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Proxima Centauri Planet

A planet in the habitable zone around Proxima Centauri? The prospect dazzles the imagination, but then, I’ve been thinking about just that kind of planet for most of my life. Proxima Centauri is, after all, the closest star to our own, about 15000 AU from the primary Alpha Centauri stars (though thought to be moving with that system). A dim red dwarf, Proxima wasn’t discovered until 1915, but it quickly seized the imagination of science fiction writers who pondered what might exist around such a star. Murray Leinster’s story “Proxima Centauri” (1935) is a clanking, thudding tale but it still evokes a bit of the magic of one of the earliest fictional interstellar voyages.

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Image: This wide-field image shows the Milky Way stretching across the southern sky. The beautiful Carina Nebula (NGC 3372) is seen at the right of the image glowing in red. It is within this spiral arm of our Milky Way that the bright star cluster NGC 3603 resides. At the centre of the image is the constellation of Crux (The Southern Cross). The bright yellow/white star at the left of the image is Alpha Centauri, in fact a system of three stars, at a distance of about 4.4 light-years from Earth. The star Alpha Centauri C, Proxima Centauri, is the closest star to the Solar System. Credit: A. Fujii.

More recently, Stephen Baxter pretty much nailed Proxima Centauri b in his depiction of a just over one Earth-mass planet in the habitable zone called Per Ardua — this was in Baxter’s 2015 novel Proxima. Baxter’s planet was at 0.04 AU, and a little more massive than Earth; the real thing is 0.05 AU and 1.3 Earth masses. I would call that very nice work. Baxter has also noted, with considerable justification, that if we find a truly habitable planet in the very next system to our own, the implication is that such planets are quite common.

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Image: This image of the sky around the bright star Alpha Centauri AB also shows the much fainter red dwarf star, Proxima Centauri, the closest star to the Solar System. The picture was created from pictures forming part of the Digitized Sky Survey 2. The blue halo around Alpha Centauri AB is an artifact of the photographic process, the star is really pale yellow in colour like the Sun. Credit: Digitized Sky Survey 2. Acknowledgement: Davide De Martin/Mahdi Zamani.

Having been at the Breakthrough Starshot meetings all this week, I’m delighted to see that we now have a potential destination; i.e. an actual rather than assumed planet around one of the stars in the system nearest to us. Finding Proxima’s planet has been a long process, drilling down to the kind of measurements that can reveal its presence. Up until now we’ve been excluding larger planets in various kinds of orbits around Proxima, but the prospect of something Earth-sized in the habitable zone remained open. I hasten to add that Breakthrough Starshot has made no decisions about its target at this point, but it’s clear that Proxima b is going to be a prime contender.

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I’m going to let Guillem Anglada-Escudé, head of the Pale Red Dot project, and his collaborators describe what his team has found. Noting that uneven sampling and the longer-term variability of the star are reasons why the signal could not be confirmed from the earlier data, the researchers go on to describe these key characteristics of the planet. From the paper:

The Doppler semi-amplitude of Proxima b (∼ 1.4 ms−1) is not particularly small compared to other reported planet candidates. The uneven and sparse sampling combined with longer-term variability of the star seem to be the reasons why the signal could not be unambiguously confirmed with pre-2016 rather than the amount of data accumulated.

And here’s what we’ve been waiting to hear:

The corresponding minimum planet mass is ∼ 1.3 M . With a semi-major axis of ∼0.05 AU, it lies squarely in the center of the classical habitable zone for Proxima. As mentioned earlier, the presence of another super-Earth mass planet cannot yet be ruled out at longer orbital periods and Doppler semi-amplitudes <3 ms −1 . By numerical integration of some putative orbits, we verified that the presence of such an additional planet would not compromise the orbital stability of Proxima b.

Image: Guillem Anglada-Escudé, head of the Pale Red Dot project and lead author of the paper on the discovery of Proxima Centauri b.

And there we are, our first assessment of a planetary system around Proxima Centauri. The team’s analysis taps into previous Doppler measurements of Proxima Centauri coupled with the follow-up Pale Red Dot campaign of 2016. The Doppler data draws on the HARPS (High Accuracy Radial velocity Planet Searcher) spectrometer and UVES (the Ultraviolet and Visual Echelle Spectrograph). The search methods and signal assessment are thoroughly discussed in the paper (citation below). Key to the effort was what Anglada-Escudé and team call “[a] well isolated peak at ∼11.2 days” that appeared in the pre-2016 Doppler data. The HARPS Pale Red Dot campaign was created to confirm or refute this 11.2-day signal. And confirm it they did.

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Image: This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser.

We have a long way to go before knowing whether a planet around a red dwarf like this can truly be habitable. Tidal locking is always an issue because a planet this close to its host (Proxima Centauri b is on an 11.2-day orbit) is probably going to have one side fixed facing the star, the other in permanent night. There are papers arguing, however, that tidal lock does not prevent a stable atmosphere with global circulation and heat distribution from occurring.

And what about Proxima’s magnetic field? The average global magnetic flux is high compared to the Sun’s (600±150 Gauss vs. the Sun’s 1 G). Couple this with flare activity and there are scenarios where a planet gradually has its atmosphere stripped away. A strong planetary magnetic field could, however, prevent this erosion. Nor would X-rays (400 times the flux the Earth receives) necessarily destroy the planet’s ability to keep an atmosphere.

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Image: An angular size comparison of how Proxima will appear in the sky seen from Proxima b, compared to how the Sun appears in our sky on Earth. Proxima is much smaller than the Sun, but Proxima b lies very close to its star. Credit: ESO/G. Coleman.

And then there’s the matter of the planet’s origins, and how that could affect what is found there. From the paper:

…forming Proxima b from in-situ disk material is implausible because disk models for small stars would contain less than 1 M Earth of solids within the central AU. Instead, either 1) the planet migrated in via type I migration, 2) planetary embryos migrated in and coalesced at the current planet’s orbit, or 3) pebbles/small planetesimals migrated via aerodynamic drag and later coagulated into a larger body. While migrated planets and embryos originating beyond the ice-line would be volatile rich, pebble migration would produce much drier worlds.

We can now hope for further data on Proxima Centauri b through transit searches, direct imaging and further spectroscopy. Ultimately, of course, we can think about the prospects of robotic exploration, the sort of thing we’ve been discussing here on Centauri Dreams for the last twelve years. No star is closer, and few will reward follow-up study more than this one. I need to get into a meeting and will have to let that wrap this up, but you can be sure there will be a lot more to say about Proxima and the entire Alpha Centauri system as the analysis continues.

The paper is Anglada-Escudé et al., “A terrestrial planet candidate in a temperate orbit around Proxima Centauri,” Nature 536 (25 August 2016), 437-440 (abstract).

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Comments on this entry are closed.

  • Wojciech J August 24, 2016, 13:07

    Ad Aspera Per Astra!

    Potential implications as noted are very interesting, even if not habitable it can be a stepping stone towards further exploration and colonization of the galaxy.
    Also if it is detected so closely, it means they must exist likely in great numbers. Raises questions of life and Fermi Paradox….

    • EricSECT August 25, 2016, 4:59

      And if Proxima b is NOT habitable, it may turn out to be “easy” to terraform.

  • Ashley Baldwin August 24, 2016, 13:30

    Hab zone Earth mass planets around the nearest stars ? Project Star-shot Breakthrough ?

    Well done Guillem. And Paul too.

    Centauri Dreams indeed !

  • Giulio Prisco August 24, 2016, 13:30

    Totally awesome. Now we must really push hard to achieve Starshot. I don’t want to log off before seeing the first probes on their way to Proxima’s planet/

    • Joe August 24, 2016, 18:04

      In doing some rough calculations, say Starshot is launched in 20 years. Figure 20+ years to get to Proxima B. Figure 5 years to beam a signal back to Earth. Who among us will be alive in 2060? Maybe Peter Thiel and those like him who can afford anti-aging treatments. As for the rest of us (judging by the average age at February’s Chattanooga conference), we will have to settle for Centauri dreams and the hope that our descendants find the Starshot project as fascinating as we do.

      • Raimo Kangasniemi August 24, 2016, 22:49

        I would be 83. My grandfather lived to be 82. Perhaps I will make it. ;)

        The idea of seeing actual data and photos from a flyby is something to… live for. :)

        • Giulio Prisco August 25, 2016, 1:22

          I would be 103 in 2060, so I don’t really hope to see the data coming back. But living to see the launch would be good enough.

          We should start seeing ourselves as a small part of a Mission to Proxima B, and then to other interstellar destination, and try to make our best contribution to the mission (which includes advancing science and taking care of each other here on Earth).

          Our grandchildren, or their grandchildren, will visit the stars and live there among the wonders of the universe. We are preparing the way.

          • Wojciech J August 26, 2016, 16:40

            The builders of cathedrals often didn’t see the results of their work…But were driven by ideas that allowed them to go on labouring whole lives, knowing that their descendants will see results of their work.
            I think space exploration requires a way of thinking that sees things in longer perspective…Unless we change our species dramatically by cybernetics and gene engineering, the rhythm of space will always stop our endeavours if we will think of scales measurable by human lifespans.

            • Giulio Prisco August 27, 2016, 2:57

              I totally agree! I developed the cathedral analogy (which is also in Centauri Dreams the book) in an essay titled “The Sacred Road to the Stars”:
              http://www.transfigurist.org/2016/06/the-sacred-road-to-stars.html

              I support the idea that we should “change our species dramatically by cybernetics and gene engineering” (becoming human 2.0) but I think we can develop the right attitude now, as human 1.0, without waiting for developments that could take centuries. The cathedral builders were people like us, and yet they practiced long term thinking.

              • Alex Tolley August 27, 2016, 8:33

                Does the cathedral analogy really work for space probes? cathedral builders were paid for the ongoing work of construction. The techniques didn’t change for other buildings or over time. The priests would still be doing the same work in smaller edifices.
                But a space probe is different. There is a long flight period that benefits few people. What is the incentive for scientists whose careers require getting publishable results for their careers? It seems to me that the space probe project is more suited for administration people whose careers are not determined by outcomes. Just build standard probes, launch them and then hire a team to analyze the results if needed. A rather different model than we use today, and certainly not the model cathedral builders used.

                • NS August 27, 2016, 19:22

                  Cathedrals were actually built to be immediately useful, with only some parts of them being built over the longer term. I suppose the space probe equivalent would be one that would return data about the interstellar medium while it was on its way to another star. If our descendants decide the probe is still useful they’ll keep it going, otherwise they’ll switch it off (as we often do with ours). I agree that it’s probably impossible for us to guess what will be scientifically important decades or centuries from now. Progress can be two-edged sword!

                • Giulio Prisco August 28, 2016, 1:13

                  Space engineers are also paid and could re-use their skills in science, maths, engineering, and computing, in other application fields. Also the incentive part seems pretty much the same – somebody who worked 30 years at building a cathedral could never say, look, here’s something that I started and finished.

                  I think the main point of the cathedral analogy is the similar spirit: working steadily for decades at a project whose completion you won’t see, because the project is important.

                  • Michael August 28, 2016, 14:11

                    We are seeming to see only the end point, the arrival of the probe into the target star system. An incredible amount of science can be achieved on the trip there and we will see the planets long before we get there with a suitable mirror. As I have written before we will start to see stars from different angles including transits and radial velocity changes which will help nail down the masses of planets more accurately.

                    There is plenty to see in the vast expanse of space if we care to look.

                • Ashley Baldwin August 31, 2016, 18:32

                  Reminds me a bit of the story behind the creation of the Earth in “The Hitchhiker’s guide to the Galaxy”.
                  Don’t forget the fjords .

      • Malcolm Davis August 24, 2016, 23:41

        I’d be 96… so I’d hope that we make some significant breakthrough in anti-aging technologies before 2060. Starshot is clearly the best bet to get an early look at Proxima B, and now having a destination to go to makes this project much more important.

        But we have to ask ourselves the question – what happens if as we gather more data from Earth, or Starshot arrives and sends back images and data showing a truly habitable planet, perhaps with local flora visible? I don’t think we can stop at Starshot at that point. But nor can we really explore the Proxima system with 20+ year transits. We have to find a way to get either an unmanned probe, or a crewed spacecraft there faster. I think that investment for R&D into viable interstellar propulsion to make trips of around 10 years should now be a goal.

      • Antonio August 26, 2016, 5:43

        I’m 42 now. I will be 86 in 2060. Current life expectancy in my country for men of my age is 81.5 years, but it has been increasing (for men of my age) in the last decades at a sustained rate of 3 months per year, so, even without rejuvenation, my real life expectancy would be around 91.5 years. Anyway, I think rejuvenation therapies will be available and cheap as dirt before 2040.

  • Harry R Ray August 24, 2016, 13:33

    Add 30% to it’s minimum mass and you get 1.7Me, which is what Kepler 186f is ESTIMATED TO BE! Alittle warmer, though, BUT NOT MUCH! The TRAPPIST search would ALMOST CERTAINLY HAVE DETECTED IT if it DID transit(unless it is made almost entirely of Iron). Perfect for Andrew LePage’ conservative habitable zone, although I’m betting he’s still going to give it the thumbs-down due to all of the constant flaring, but we’ll just have to wait and see. Now, I’m going to SHOCK YOU ALL! If this were ANY OTHER PLANET AROUND ANY OTHER STAR, I would be litterally PRAYING for life to exist on it, BUT NOT THIS ONE! Here’s why! I hope it’s a cooler version of Gliese 1132b, which is now theorized(but not proven) to be, NOT a Venus analog, but, instead; a nearly AIRLESS world with oxygen as its PRIMARY atmospheric component. I do not want a SINGLE SHREAD OF DNA to exist on Proxima Centauri b UNTILL WE PUT SOME THERE OURSELVES! After our sun has evolved to a White Dwarf, we could live on a TERRAFORMED Proxima Centauri b for ANOTHER TRILLION YEARS! Rather that than a sterile “megastructure” for me, anyway. I guess that makes me “old fashioned” by preferring an honest-to-God planet over an Oort cloud or O’Neil colony.

    • Harry R Ray August 24, 2016, 13:41

      I’m ASSUMING, of course, that Proxima Centauri b’ s atmosphere(or LACK of one)was a RESULT of being cooked off the planet when a YOUNGER Proxima Centauri was MUCH MORE LUMINOUS than it is now. A COMPLETE LACK OF LIFE EVER EXISTING ON IT would alleviate any POTENTIAL GUILT we as as a collective species may feel after we TERRIFORM it into Earth 2.0!

      • Michael August 24, 2016, 14:11

        It has more than likely lost a significant amount of its atmosphere due to the luminous pre-main sequence stage. Might be a super mercury than a super venus, plenty of material to build our gallatic empire and plenty of room for more planets.

      • Robert August 24, 2016, 15:08

        Any advanced technological spaced based civilization capable of terraforming a planet would most likely not need or want to bother to do so.

        • Zanstel August 25, 2016, 5:28

          We are humans. Not always rational.
          An ET could ask humans… why are you making so expensive modifications on this planet? The galaxy is plenty of better planets!

          Well… It’s very near of my house. We like to make gardens near our home, and that was a barren place.
          We make it not because it’s easy because it’s hard!

          • Harry R Ray August 25, 2016, 9:50

            OOPS: I guess the OFFICIAL designation is going to be just Proxima b. Bad news and good news. Davenport, Kipping, et al just submitted their “MOST data Proxima Centauri paper to Arxiv, and there is no mention of transits whatsoever. The only hope is that they propose that the CONSTANT small flares MAY have PREVENTED TRAPPIST from detecting any transits of Proxima b(although, if this IS true, why were they able to detect any transits at TRAPPIST-1?), and the transit issue will have to be resolved by space telescopes like Hubble and Spitzer. RUMORS: ANOTHER POSSIBLE planet signal APPEARS to be in the data. Just looking at the graph, if the signal is REAL, it is of a much larger planet, much farther out, just the KIND of planet the February microlensing/mesolensing event could EASILY detect. Also, we MAY not have to wait for New Worlds Observer to get an image of Proxima b. As soon as JWST launches, a much less sensitive “prototype” version could be built VERY QUICKLY and quite possibly do the trick. ANY TAKERS? It seems like this is JUST THE SORT OF THING The Planetary Society would be interested in doing.

            • EricSECT August 25, 2016, 17:12

              How about another “Kickstarter” to raise donation money, like we just did for Tabby’s Star?

              • Harry R Ray August 26, 2016, 9:35

                The Planetary Society has MILLIONS of members! If they INITIATE initial construction of a rudimentary starshade AFTER(NOT before)JWST has achieved orbit and is functioning flawlessly, you would NOT need to KICKSTART. I and many many thousands of members would donate IMMEDIATELY! Any reader of this posting who is NOT YET A MEMBER SHOULD JOIN so that your INPUT could add this to their other projects, like their lightsail.

                • Robert August 26, 2016, 11:48

                  Are you not aware that using all caps is like screaming. You don’t need to scream for emphasis.

                  • Michael August 26, 2016, 15:00

                    It is his STYLE, let him be! and I can’t be bothered to get a Kickstarter project going to get him a new keyboard.

                    • Rob Henry August 26, 2016, 19:12

                      More’s the pity as many would give generously to that.

                • Ashley Baldwin August 29, 2016, 7:13

                  It’s not as easy as that unfortunately. To use a star shade a telescope needs numerous adaptations for “formation flying ” . Not many and costing no more than a few tens of millions of dollars to be fair ( versus the $8.5 billion it cost to build ) , but vital for functionality .

                  The exoplanet fraternity tried very hard over an extended period to do this , but to no avail. As far as the budget was concerned , and it’s overspend , not a cent more . A shame because it could have imaged a lot of interesting planets , including Proxima b. The other problem is due is the starshade itself . The Exo-S Probe starshade telescope study showed that a 37m shade was estimated to cost about $63o million to build. That was for a WFIRST class 2.4m scope. At 6.5 m JWST would need a 50m plus shade with all its extra cost and launching difficulty given its size though it would at least be lightweight. Would probably require a modified ( a fairing size increase from 5 to 6.5m ) Delta IV Heavy to get it to L2 also at $385 million per launch. Role on the Falcon Heavy !?
                  The case to get WFIRST ” starshade ready ” goes on meantime with a view to keeping the option of using one open should funds be available later. The concept has already moved orbit from geosynchronous to L2 which has been seen as a concession for a starshade , but already it has irritated some as a recent “independent report” of the WFIRST formulation process was ominously critical of its increasing price which was clearly ( by the report ) connected with incorporation of a coronagraph and to the telescope”s its orbit move to more remote L2. Caution advised !

            • Ashley Baldwin August 30, 2016, 8:20

              Can’t image Proxima b with a telescope with an space telescope aperture less than 4m unfortunately. Bendek et al article on “ACEsat” has a nice graph illustrating this with very readable supporting text on small, bespoke telescopes. It’s because of the very narrow habitable zone of M dwarfs , the later they are the worse it is and Proxima is an M5.5 , versus say G2 Alpha Centauri A And K 1 B which can be imaged with enough time . Even Proxima’s proximity can’t make up for it and even 2.4m WFIRST isn’t big enough unfortunately .

              All may not be lost though until we have the ELTs to image the planet in a decade . Clever extended “high dispersion spectroscopy” ( a potent combination of high resolution optical spectroscopy and high definition imaging ) from ground and space ( as described on this site in Snellen’s ” Here come the Giants” article) scopes should at least be able to tell us the whether the planet has an atmosphere ( in itself a hugely important discovery ) and possibly even identify an ozone layer too if one is present ( indirectly implying a high O2 content to atmosphere ) . Not bad for starters and if achieved probably Nobel prize material.

      • EricSECT August 26, 2016, 6:49

        I think that we, as a species, need to get over this “potential guilt”. We can wisely do both: Transform “easily” terra-formable planets to suit our needs while being good stewards AND accommodate extant life that we may find there. Create a reserve, a sanctuary, etc. for the life we find. After all, if we win “the race” in technological development and ability to star travel, we should get to call the shots.

        • hiro August 26, 2016, 17:52

          Anything within a radius of 500 ly is almost a fair game. However if we expand too quickly after that “boundary”, we might be dragged into the interstellar war game with some unknown players. I think this is one of the reason advanced civilizations don’t do colonization the entire galaxy because the resources are wasted more than the receiving benefits after crossing certain distance from the home star system due to useless & unwanted games of damage.

          • Harry R Ray August 29, 2016, 19:55

            KIC8462852? GULP! We’ll ALL know how THAT will end up.

    • Andrew LePage August 24, 2016, 15:14

      “Perfect for Andrew LePage’ conservative habitable zone, although I’m betting he’s still going to give it the thumbs-down due to all of the constant flaring, but we’ll just have to wait and see. ”

      Want to place a wager? I have already started working on my review :-)

      • Kappy August 24, 2016, 22:02

        I rather think you will tell us that with a min 1.3Me and likely somewhere closer to 1.6-1.7Me that this is much more likely a mini Neptune than a Super Earth. I’m hoping for a habitable exomoon, which isn’t impacted by tidal locking.

        • Kappy August 24, 2016, 22:06

          Edit: I confused mass and radius here. Seems the planet is likely less than 1.6Re making it most likely a terrestrial world.

          • Eric August 25, 2016, 0:30

            Note: it it is a mini-Neptune, then maybe the flaring will be a good thing, at least with respect to life. Flaring could gradually strip away too much atmosphere and leave a more hospitable residual atmosphere until Proxima Centuri calms down over time and flares less.

        • Andrew LePage August 25, 2016, 9:36

          The work by Rogers and others suggest that planets transition from being more than likely rocky to being volatile rich at a a radius of ~1.5 RE which corresponds to a mass of ~6 ME, assuming an Earth-like composition. With a Msini value of 1.27 ME, Proxima b has ~98% chance of having an actual mass below this value. More recent work by Chen and Kipping suggests that the gradual transition from rocky to volatile-rich planets seems to start at ~1.2RE or ~2ME. With an unconstrained orbit inclination, the odds that the actual mass of Proxima b is less than this value still ~77%. The odds seem to heavily favor Proxima b being a rocky planet like the terrestrial planets of our solar system.

      • spaceman August 25, 2016, 10:41

        Hi Andrew,

        My first guess is that the planet may have had its atmosphere stripped by high energy radiation emanating from the parent star. On the other hand, I could imagine a scenario in which the planet formed further out and then migrated to its current position after the star quieted down. This latter possibility might mean there is still an atmosphere, but an atmosphere made out of what who knows. I watched the coverage of this discovery on the PBS New Hours and Miles O’brien talked about how if the planet is found to have liquid water, then there may be a good chance of finding life because wherever there is water on earth there is Life present. I am of the view that the presence of water may not automatically imply life, but it would sort of be hard for the mind, my mind at least, to imagine planets with large amounts of completely sterile liquid water though I guess that the lack of exobiological contamination might make it safer to drink.

        Since you are a scientist working in the exoplanet field, I was wondering if you had heard about a recent paper claiming that the Kepler team’s occurrence rates for terrestrial planets (not just giants) may have been overestimated by as much as a factor of 2-4! Here is a link to the paper: https://arxiv.org/pdf/1608.05410.pdf Does this seem right to you, that the occurrence rates could be off by this much? That would seem like a pretty big discrepancy.

        • Andrew LePage August 25, 2016, 15:23

          Yes, I saw the paper a few days back but it isn’t saying that Kepler’s rocky planet occurrence rates are incorrect. Instead the paper suggests that there is something wrong with the widely held view that the presence of warm dusty debris around young stars (which is observed 2-3% of the time) is associated with the formation of rocky Earth-mass planets at AU distances (which can be found around ~20% of stars). Either the two are not related after all or dust is cleared out faster then believed after rocky planet formation or planet formation is not quite as dusty as supposed or something else we do not fully understand is going on.

  • Lionel Ward August 24, 2016, 13:36

    Seems that Centauri Dreams do come true!

  • Alex Tolley August 24, 2016, 13:40

    If you don’t have access to Nature, you can view the full paper using this link: A terrestrial planet candidate in a temperate orbit
    around Proxima Centauri
    .

  • Coacervate August 24, 2016, 13:42

    I presume you will take your office somewhere along the terminator. Thanks for keeping this candle burning a bit brighter day by day.

    • Harry R Ray August 25, 2016, 9:59

      Actually the two POTENTIAL HZ’ are NOT at the terminator. HZ1 would be just OUTSIDE the stellar point IF(AND ONLY IF) the planet IS tidally locked. HZ2 would be in “belts” NEAR the equator IF(AND ONLY IF) the planet’s rotation period is similar to Mercury’s. I’m sure Andrew LePage will have a lot more details in his upcoming post.

  • DJ Kaplan August 24, 2016, 13:54

    Already there is a Wikipedia article dedicated to this. Any eager editors out there?
    https://en.wikipedia.org/wiki/Proxima_Centauri_b

  • DJ Kaplan August 24, 2016, 14:02

    Would this star’s proximity to the Earth make the exoplanet a good candidate for direct imaging?

    • Joy August 24, 2016, 17:16

      Yes and no. The small angular separation raises the difficulty, comparable to trying to resolve the Earth from 80 light years away. It is also unfortunate that being a cool star with a high fraction of infrared radiation, that the colour difference between Proxima and the planet is less than the Earth-Sun colour difference, so the advantages of doing infrared imaging are less. No existing instrument could hope to resolve this planet.

      The good news, for (younger) people living now is that the combination of the failure of the $17 billion and counting LHC to produce any physics beyond the standard model and this discovery will argue for the next multi billion dollar science project to be a truly colossal telescope. Even if Proxima B turns out to be boring, the science return on investment in new telescopes is still huge. Go astronomy!

      • Ashley Baldwin August 30, 2016, 18:12

        What would be a nicer still would be a still big if not colossal , circa 12m ” all rounder ” non cryogenic LUVOIR telescope ( but starshade adapted for special cases ) AND a 5-6m bespoke , modular and monolithic, off axis exoplanet imager with state of the art coronagraph , starshade and various low-medium resolution spectrographs covering a respectable 0.4-12 microns bandwidth that avoids the need for life limiting cryogenics . Both tried and tested designs with minimal need for expensive development and fitting into ample fairing room of cheap new heavy launchers . Also equipped with powerful next gen ion thrusters to help return them to LEO for convenient low risk servicing when required .

        Exoplanets need long observations of up to several months and that is never going to happen on any shared scope so it’s worth sacrificing some aperture to get a scope that can still characterise planets around most stars within 50-100 light years without interference from other astrophysics projects . The scope could do transit spectroscopy as required. But wouldn’t break the bank. The two scopes could cross cover on occasion whilst one serviced or do joint imaging on exceptional targets .

        Maybe one day in future , technology allowing their star shade hardware could be adapted to link them up with numerous smaller scopes as part of a large space interferometer .

    • Ashley Baldwin August 24, 2016, 17:51

      The proximity helps but it’s still a big ask. The angle subtended by the planet is less than 50mas at quadrature , so would need a big telescope or purpose built space scope , maybe HabEx or the next generation LUVOIR scope if equipped with a suitably Uber high stability and high contrast occulter . Internal or external. Could be a while.

      The lucks in so far though , so here’s to hoping that meantime a circa 1.5% chance of a transit comes good . If it does then TESS and JWST particularly can get at it. It’s for things like this MIT are hoping for with TESS though even then to get enough transits to characterise on non dedicated JWST would depend on where Proxima sits in its field of view. This would vary from not a lot to a small area graced with all year coverage . That would be pushing things , but you never know.

      A great incentive to build something that can characterise any planets?!

      If there’s one ,as the author’s state and has been shown by Kepler et al, there’s likely to be others too.

      • Raimo Kangasniemi August 24, 2016, 22:56

        Let’s not forget ESA-Swiss’ CHEOPS and ESA’s PLATO going up in 2017 and 2024. Both of these space telescopes could observe transits’ (even Canada’s suit-case sized’ MOST have tried it for Proxima).

      • Michael C. Fidler August 25, 2016, 9:11

        So no chance a Super ACEsat would work?

        • Ashley Baldwin August 26, 2016, 12:38

          Excellent point. You’ve read my mind . Maybe is the answer. ACEsat could achieve contrasts of 4e11 and Inner Working angles, IWAs, of down to 40 mas for the Alpha Centauri B hab zone . ( 0.6 AU- 1 AU) . It had a 45 cm mirror and observed nothing bar Alpha Centauri for two years . It’s novel ,indeed unique Multi star wavefront control system ,MSWFC, allowed it to simultaneously image both stars of the binary “primary” . The long observation allowed Orbital differential imaging, ODI, via 20 k photographs of the system to help increase sensitivity in building up the final image from the initial crude images . “Post processing” that allows a reduction in how much of the contrast differential between the star and planet had to be produced by the coronagraph . This last being the most difficult and expensive to build and run of the entire telescope with silicon carbide construction throughout ( like the Herschel space telescope ) also helping keep costs down to a very reasonable “small” Explorer programme $120 million. For what was a unique telescope.

          The big Explorer fund ( conveniently due this year) is $250 million and thanks to WFIRST research much of he technology has matured ( a factor in ACEsats non selection ) . Could it be beefed up enough ? Bigger , yes, perhaps 1m. Spectrograph for more detailed characterisation? ( the original didn’t have one but Imaged in five separate wavelengths of important bio signatures like Rayleigh scattering from an Earth like atmosphere and methane .) Hopefully .

          The key is the best IWA. Proxima Centauri is much dimmer than its A/B neighbours so contest isn’t a problem. ( how much dimmer a planet you can see in relation to its parent star). The best IWA for ACEsat was 40 mas for Alpha Cent B . Proxima b is 28 mas from its star. Can it be done ? Maybe for a bespoke scope looking at just it without worrying about other stars (though Alpha Centauri A/B would be the obvious follow on) . Timing will never be better. No risk of coming up blank as with the original ACEsat at Alpha Centauri A/B so no shooting in the dark at all your eggs in one basket.( another reason the original was rejected) .

          WFIRST can’t image Alpha Centauri without ACEsats MSWFC and JWST won’t see Proxima b unless it transits ( 1.5%) . E-ELT with the EPICS spectrograph can, but not till 2029 earliest. That’s a long time for a very obvious target , one that’s very near which ultimately is the reason that ACEsat works so well. If given the chance .

          So we shall see…….

          • Michael C. Fidler August 27, 2016, 3:20
          • Ashley Baldwin August 29, 2016, 7:41

            Reading up on the ACEsat spec ( which the team published in detail) , even an enhanced ACEsat with say a 1.2m ( might fit within available astrophysics programme budgets ) telescope , would not have enough resolution to see Proxima b.

            Alpha Centauri A/B , it’s principal target has a uniquely wide hab zone as seen from Earth , partly because of its suitable stars but also thanks to its proximity. Proxima is close too of course , but as a late , cool M dwarf ,has a very narrow hab zone . Even 2.4m WFIRST with a starshade couldn’t see it. It needs a minimum 4m aperture space scope like HabEX . Might be a good boost for ACEsat in terms of Alpha Centauri A/B which still haven’t been found to have a planet despite being so near.

            What better time on top of Starshot Breakthrough than to submit a revised and enhanced ACEsat ? Such is their motivation , that the designers have been trying hard to get private funds for a toned down mission, Centaur , based on a large Cubesat , but Proxima b might change things .

            Might even be something the Starshot committee could help them with . If you are planning a mission somewhere and it needs funds , best to know what you are aiming for especially if it is exciting . Imagine the effect of finding an Earth sized hab zone planet around A or B, and unlike Proxima b, being able to see and characterise it immediately . What better incentive . The original highly capable 0.45 m ACEsat telescope could do this , and only came in at $120 million . For added value it could also have imaged Sirius,Altair and Procyon.

            What could a bigger telescope $250 million Medium Explorer mission with a proper spectrograph achieve ?

            So it’s either JWST on the faint chance of a transit or wait till the E-ELT is operational with its EPICS package ( the successor to the VLT’s SPHERE , combining a 1e8 coronagraph, extreme adaptive optics and a visible /Near infrared spectrograph . Resolution ~ wavelength / telescope aperture , so shorter wavelengths give better resolution than say Mid infrared . )

    • Raimo Kangasniemi August 24, 2016, 22:53

      Yes, combined with Proxima being a rather feeble star. A decent space telescope with a fitting star-shade (even when Proxima b is orbiting very close to the star) could pick it up, although some people are claiming that ESO’s own new 39.3 telescope becoming operational in early 2020s should be able to directly imagine it.

      • Raimo Kangasniemi August 24, 2016, 23:00

        39.3 meter telescope of course.

      • Ashley Baldwin August 26, 2016, 13:17

        Not until it has a potent 1e8 coronagraph and suitable adaptive optics package it won’t . And a visible /near infrared spectrograph too, ( longer wavelengths don’t give the resolution required even for a telescope this big) all as one package. That is planned as EPICS, but unfortunately as a second generation instrument ( partly cost , partly incredibly difficult development and processing power required ) won’t see “first light “until 2029 at the earliest. Same with TMT though that hasn’t started building yet.

        ELT has the similar METIS tool as a first light instrument but this operates at wavelengths too far ( and long. Resolution ~ wavelength/Aperture , so 450 nm blue light gives 10 times better resolution than 4500 nm (4.5 micron) mid IR light ) into the IR to resolve Proxima b. It may work on larger , brighter planets further out from primary though , perhaps around nearby early M0/1 dwarfs rather than poor M5.5 Proxima. “Calmer” too. What TESS is after effectively .

    • ljk August 25, 2016, 9:21

      Next Big Future has a list of the telescopes that could image and monitor Proxima Centauri B with details, here:

      http://www.nextbigfuture.com/2016/08/upcoming-telescopes-that-will-provide.html

      The list:

      * James Webb Space Telescope (2018)
      * 24 meter ground based telescope, Giant Megallan (2022-2025)
      * 39 meter ground based Extremely Large Telescope (2024-2027)
      * 30 Meter Telescope (permit delays, around 2022-2025 if resolved)
      * Proposed 12 meter High definition space telescope (could spot earth sized planets out to 45 light years and directly image Proxima B). If funded could get built by 2030 or so.

      • DJ Kaplan August 25, 2016, 12:42

        Thanks, all!

      • Joy August 25, 2016, 14:49

        Asterisk! – Each of these proposed or under construction projects would require a coronagraph or starshade to image Proxima b. But yes, this is doable in under 20 years, even though large telescopes are never completed on schedule. The mighty ELT is a construction site, with instruments still in the design phase.

        • Ashley Baldwin August 30, 2016, 18:26

          EPICS is the second generation instrument for Proxima b on E-ELT. Essentially the descendent of SPHERE on VLT. An Optical/NIR spectrograph/extreme adaptive optics /1e8 contrast coronagraph package . METIS similar but images in the Mid IR (L-N band) so won’t be able to image Proxima though maybe some bigger , further out nearby planets . Designers not happy with choice of Cerro Amazones as site for E-ELT as not as good as others for thermal IR imaging given background . Would have preferred Atacama desert site near ALMA ( but higher ) or Dome C at Antarctica . For all its inaccessibility, lack of infrastructure and hostile climate it possesses viewing mid way between the best mid latitude sites and space ( once you get 30m up above ground turbulence )

      • Ashley Baldwin August 26, 2016, 13:27

        The science definition teams from Nasa are already meeting to talk about the telescope to follow WFIRST. That will inform Decadel 2020. With WFIRST due to launch circa 2024/5 I can’t see it launching till a decade after that sadly . Whatever form it takes and both X Ray and Far IR scopes are in the mix , both far from suitable for exoplanets .

        I think the ground based scopes are a good bet ,eventually . Shorter term WFIRST-S with a star shade ( and multiple star system imaging software ) a possible though a bespoke Proxima /Alpha Centauri ACEsat scope might surprise us meantime. Takes advantage of the system’s unique proximity to keep aperture and thus telescope costs down hugely . ( also close ,promising Tau Ceti, with multiple proven planets is nearly three times further away!)

        Here’s to hoping .

        • George King August 28, 2016, 23:45

          PEACEsat

          Proximate Exoplanet [and] Alpha Centauri Explorer Satellite

          “The Little Telescope That Could”

          Yes, here’s to hoping that we see that.

  • Alex Tolley August 24, 2016, 14:05

    To have a potential rocky world so nearby should be inspiring. If future spectral data show signs of water and an atmosphere, then this would be a certain target for a probe.

    Greg Benford’s short story “The Man Who Sold the Stars” (Starship Century) went for a brown dwarf as the target. With this Proxima data, future stories by authors will pehaps be more biased towards this star.

    • ljk August 25, 2016, 9:19

      It is still quite possible that there are brown dwarfs (with their own planets) and rogue exoworlds closer to the Sol system than Proxima Centauri, so I would not rule them out any time soon. And maybe some alien Worldships and Matrioshka or Jupiter Brains passing through the neighborhood. :^)

      Also, do not forget the giant so-called Planet Nine that may exist way out in the Kuiper Belt, not to mention other similar large worlds we have yet to find in that distant and dark realm. Is Nemesis still a thing?

      A new paper relevant to the topic:

      https://arxiv.org/abs/1608.06719

      Search for exoplanets and brown dwarfs with VLBI

      K. Katarzynski, M. Gawronski, K. Gozdziewski

      (Submitted on 24 Aug 2016)

      The main aim of this work is to estimate possible radio GHz emission of extrasolar planets and brown dwarfs and to check if such radiation can be detected by Very Large Baseline Interferometers (VLBI). In the estimation we assume that the emission may originate in processes similar to those observed in the Jupiter system. The frequency of the radio emission that is produced in this system depends mostly on the magnetic field strength. Jupiter’s magnetic field (∼9 G on average) allows for radiation from kHz frequencies up to 40 MHz. This is well below the frequency range of VLBI.

      However, it was demonstrated that the magnetic field strength in massive and young object may be up to two orders of magnitude higher than for Jupiter, which is especially relevant for planets around short-lived A type stars. This should extend the range of the emission up to GHz frequencies.

      We calculated expected flux densities of radio emission for a variety of hypothetical young planetary systems. We analysed two different emission scenarios, and found that the radiation induced by moons (process similar to Jupiter-Io interactions) appears to be less efficient than the emission generated by a stellar wind on a planetary magnetosphere.

      We also estimated hypothetical emission of planets and brown dwarfs located around relatively young and massive main sequence A-type stars. Our results show that the emission produced by stellar winds could be detected by currently operating VLBI networks.

      Comments: 11 pages, 5 figures

      Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

      Journal reference: 2016 MNRAS vol. 461 p. 929

      DOI: 10.1093/mnras/stw1354

      Cite as: arXiv:1608.06719 [astro-ph.EP]
      (or arXiv:1608.06719v1 [astro-ph.EP] for this version)

      Submission history

      From: Krzysztof Katarzynski [view email]

      [v1] Wed, 24 Aug 2016 05:32:49 GMT (218kb,D)

      https://arxiv.org/pdf/1608.06719v1.pdf

  • Wojciech J August 24, 2016, 14:42

    A good article on habitability of Proxima b:

    http://www.ice.cat/personal/iribas/Proxima_b/indepth.html

  • Michael August 24, 2016, 14:46

    Of interest is the long rotation period of Proxima, planets love to rob angular momentum from stars and I think there are more planets in this system.

    • Raimo Kangasniemi August 24, 2016, 22:58

      The data hints at another Super-Earth orbiting well beyond the habitable zone.

    • DJ Kaplan August 25, 2016, 12:46

      You don’t think that might be coming from the Alpha cen binary?

  • Michael Morris August 24, 2016, 15:12

    Interesting we find a small rocky theoretically in the habitable zone in the next star to us. It could suggest there are way more of these within a 50 ly distance from Sol.

    • Wojciech J August 24, 2016, 18:32

      This is one of the important implications that need to be raised.
      If we found a rocky planet in HZ just around next star to ours, it probably means they are widespread. This has consequences on our search for life and Fermi Paradox.

  • RobFlores August 24, 2016, 15:28

    We need to not just send One probe to the Centauri system.
    That being said We need to set up an assembly line of probes,

    We need some insurance at least twin probes should be sent (close enough to each other that they can share resources for repair should the hostile space environment partially cripple both.

    Because Life is full of disappointments We can’t just assume we will hit
    close to Jack pot on P Centauri. The flaring potential of Proxima hangs over this discovery. Even if it does have Lakes or a modest Ocean, (I doubt it, with all that flaring) It is strictly a candidate for subterranean type colonization.

    The question is it more hostile than Mars or Titan?

    Don’t get me wrong I welcome the shot to the arm this will bring to interstellar flight projects.

    Also, There are other close targets that should be considered as well.

    Episilon Eri.
    61 Cygni
    Epsilon Indi
    Tau Ceti.
    As we gain experience in design and tech advancement in miniaturization these systems will not seem so far. As a matter of fact I predict the 1st probe
    sent to E. Eridani will travel 2x as fast the 1st one to Proxima C.

    • Wojciech J August 24, 2016, 18:33

      Well I heard that Pale Red Dot team will encourage projects like this to be done on other stars.
      I also think there was an idea of sending out mini-satellite telescopes to observe just one star in search of exoplanets.

  • Richard Flapper August 24, 2016, 15:37

    Well now, I’d say, as a token of appreciation towards Stephen Baxter, this planet should be called Per Ardua!

    • EricSECT August 25, 2016, 5:14

      I second this motion!

      • Harry R Ray August 25, 2016, 10:06

        SORRY: Proxima Three! I’m a HUGE “Babylon Five” fan! That’s wh I was SO BUMMED that Davenport, Kipping et al found no transits. Still betting on Hubble, Spitzer, or JWST to find something.

    • Giulio Prisco August 25, 2016, 11:44

      I thought the same after noticing the similarities between Proxima b and Per Ardua (which in Baxter’s novel is Proxima c).

      By the way here’s my review of Baxter’s Proxima:
      http://io9.gizmodo.com/take-a-wild-trip-to-our-nearest-stellar-neighbor-in-pro-1535403681

      The novel continues with the sequel Ultima (highly recommended). No third novel is expected, but if you have read Ultima, don’t you think that the ending clearly calls for a sequel?

      • ljk August 25, 2016, 15:57

        Not to be rude, but while Baxter is described as a “hard science” science fiction author, I find these kinds of things, as quoted from your piece next, no better than Star Trek dilithium crystals or being just this side of outright magic:

        “The “Ad Astra” starship is powered by “kernels,” mysterious objects recently discovered by the UN’s International Space Fleet (ISF) buried in the rock of Mercury, perhaps the products of alien technology. The kernels, programmable wormholes, can extract energy from remote places – for example from high-energy astrophysical events – and take the starship to Proxima Centauri in only a few years at near-light speed.”

        Maybe some day we will find advanced alien technology somewhere in the Sol system that will improve our civilization dramatically, but I am not placing bets on it nor am I willing to wait indefinitely for any kind of FTL drive while we can develop our own legitimate interstellar propulsion methods, even if they are – gasp! – slower than light speed.

        Thank goodness for Breakthrough Starshot and Project Orion – yes, the one with the exploding nuclear bombs for fuel.

        • Giulio Prisco August 25, 2016, 23:50

          Well, the kernels are needed for other aspects of the plot as well, so why not using them also for propulsion.

          Baxter is a hard science fiction writer indeed, and in my opinion one of the best. As you say, he describe things “just this side of outright magic,” but what’s wrong with that? Baxter stays “this side” and compatible with the scientific worldview. Note that great technological advances, from the sail to the internet, have always been “just this side of outright magic.”

          • ljk August 26, 2016, 9:57

            I would rather see some effort made to come up with a realistic method of propulsion, since he is supposed to be hard science SF. Otherwise this might as well be magic and that is neither science nor science fiction but space opera fantasy, and we have more than enough of them.

            Mysterious aliens leaving even more mysterious devices buried on an alien planet is really no better than the unexplained hyperdrive in Star Wars and countless other science fiction/fantasy stories. It waves away the real technical problems without having to address them.

            Such plot mcguffins also promote the copout that one day either our human descendants or altruistic aliens will just happen to figure such things out because they are from the future and therefore must be more advanced, smarter, and kinder. I am sure the ancient Romans once thought their future would behold a continuation and improvements upon their civilization. Surprise.

            You can tell me that one day we may indeed have portable wormholes to flit around the Cosmos with, but until someone can actually figure out how to build such things, they remain a fantasy and do those of us who live in this world and are striving for real interstellar travel little good.

            Here’s a place for those who want some science in their science fiction:

            http://www.projectrho.com/public_html/rocket/

            • Giulio Prisco August 26, 2016, 11:49

              Baxter is a writer, not an program manager. His role is different.

              I think highly imaginative speculations, as long as they remain essentially compatible with science, do _a lot of_ good to those “who live in this world and are striving for real interstellar travel.” They keep us dreaming, and dreams motivate and give energy to overcome challenges.

              • ljk August 26, 2016, 13:41

                “If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them.” – Henry David Thoreau

                http://thoreau.eserver.org/jimmy2.html

                • Giulio Prisco August 27, 2016, 2:51

                  This is a GREAT quote, thanks for sharing! Now, I don’t know how you interpret it, but to me it says that it’s OK to let visionary imagination run wild and scout strange places, provided you then build bridges to reality and achieve your visions.

                  Here “you” means us, our society, because very few people have both sets of skills. Typically, it’s other people who build on the work of the scouts.

                  In our context, I think the work of those who scout the fringes of physics to find new approaches to space propulsion has value. Most of them will fail, which is the price one pays for going off the beaten path, but some of them will find something that practically-minded engineers will exploit, sometimes with spectacular results.

                  In conclusion, the world needs both practical engineers and visionary dreamers, and the two groups should respect and support each other.

                  • ljk August 29, 2016, 12:00

                    Glad you like the quote. It is among Thoreau’s most famous.

                    Not arguing your points, I just want a novel that purports to be written as hard science fiction to not shy away from its concepts; the author needs to give at least SOME scientific/technical explanation.

                    Saying they found some strange alien device by chance with no idea how it works then having it get used anyway to move the plot along is not science fiction but fantasy. Many otherwise “hard” SF stories are guilty of this.

                    See my point about Jules Verne and his Moon novels below.

              • ljk August 26, 2016, 14:03

                A prime example of an SF novel where the author not only did his homework for every detail but still managed to have a good and even entertaining plot and characters were the classics From the Earth to the Moon and Round the Moon by Jules Verne:

                http://www.gutenberg.org/ebooks/12901

                Yes he used a 900-foot deep cannon to propel his explorers to the Moon (three of them from Florida, please note), but the point is Verne did his level best to be as accurate as possible using what was known to science in the mid-Nineteenth Century. We forgive him for his errors because he did not try to wave away such advanced concepts as sending humans to the Moon.

                Same for most of his other such works, especially this one:

                http://www.ibiblio.org/julesverne/books/20t.htm

  • H. Floyd August 24, 2016, 15:47

    Congratulations, Paul! There’s no denying that you are permanently associated with this finally materializing vision, and share bold company with our tallest space science dreamers, all correctly “hoping an inch of good is worth a pound of years.”

    • Paul Gilster August 24, 2016, 16:36

      Very kind, sir! I can’t claim anything but a peripheral role, but what a pleasure it continues to be to write about this work and the people who achieve it. I’m with a bunch of them right now and it’s a humbling experience. Also a very energizing one!

  • Hop David August 24, 2016, 16:35

    Interplanetary travel would be a little different in a red dwarf system.

    The earth orbits the sun at 30 km/s. If this Earth2 orbits Proxima Centauri in a .05 A.U. circular orbit, I get 47 km/s. Escape velocity from the star at that distance would be 66 km/s (vs about 42 km/s to escape from the sun at 1 A.U.).

    In my spreadsheet I stuck in a Mars2. 1.52 times the distance from the star as Earth2. I made Earth2 and Mars2 1.3 times the mass of their sol counterparts. Radius I made 1.3^(1/3) times the radius of their counterparts.

    My spreadsheet relies solely on the vis viva equation so it doesn’t take into account aerobraking. Nor does it give gravity loss incurred in vertical ascent through an atmosphere. It gives 17 km/s between Earth’s surface and Mars’ surface. But 20 km/s between Earth2 and Mars2. I had expected the delta V to be a lot higher, still checking my arithmetic.

    Launch windows and trip times are a whole lot nicer. Earth2Mars2 synodic period I get 25 days (vs 2.14 years for Earth and Mars). Trip times for Earth2 and Mars2 is 8.3 days vs 8.5 months for Earth and Mars.

  • Geoffrey Hillend August 24, 2016, 16:40

    An 11. 2 day orbit is not a long time so it should take to long to do transit spectroscopy or even direct imaging spectroscopy. The detection of H2O in the atmosphere would be interesting. A thick atmosphere might block a lot of the x-rays however as written in this article if the planet does not have a strong magnetic field like our Earth, the solar wind could be cause a loss of atmosphere. How strong is the solar wind of Proxima Centauri compared to our Suns at one AU?

    There should still be some atmosphere around Baxter’s planet though and the atmospheric composition will tell us whether or not it has a strong magnetic field and if a serious atmospheric stripping is happening.

  • Geoffrey Hillend August 24, 2016, 16:41

    I meant it shouldn’t take long to do transit spectroscopy.

    • ljk August 25, 2016, 11:40

      Why did it take so long to find Proxima Centauri b?

      http://www.space.com/33845-why-proxima-b-exoplanet-hard-to-find.html

    • DJ Kaplan August 25, 2016, 12:49

      Yes, once a transit is detected.

      • Ashley Baldwin August 26, 2016, 12:42

        A 1.5 % chance of a transit for this planet. Rs( radius of star in kms ) / a ( semi major axis of planet in kms ) gives chances as a fraction roughly .

        Even if it does , the star’s multiple flares are likely to make it difficult to see let alone detailed transit spectroscopy .

        • Michael August 26, 2016, 15:30
          • Ashley Baldwin August 26, 2016, 17:11

            Do you know, whilst part of me wants Proxima b to transit and thus fall within the ambit of JWST ( assuming the transit can be seen and the limited time allocated for exoplanet studies on JWST allows the twenty or so required to do spectroscopy . Largely dependent on where the star falls within JWST’s observational field) , part of me wont be disappointed if it doesn’t as I think the temptation of having a planet , but not just any planet , an Earth sized planet in the habitable zone, of the nearest star , will all prove too much and someone will come up with a way of imaging it within available funds and well before the ELTs get to it late next decade

            . Too long to wait. It’s the ultimate scientific discovery and to not characterise it , the implications of which can only be interesting and groundbreaking no matter what, would be bordering on a crime when the technology is available . It’s there, staring us all in the face , and just asking to be scrutinised in the detail it deserves.

            Something will give ….

  • Lionel Ward August 24, 2016, 18:16

    Does anyone have any info on the expected range of tectonic activity on Prox-B? Here’s two factors I’m thinking might make it be a lot higher than on earth:
    i. planetary mass of roughly 1.3 ME
    ii. expected levels of tidal forces on the planet gives its 0.05 AU from Proxima Centauri

    • Ashley Baldwin August 26, 2016, 17:25

      At 1.3 Me you would expect any planet to have greater residual heat of formation and also radionuceotide burden ( U235/238, Th 232, K40) which should drive convection and in turn tectonics . Not to big to compress the mantle and suppress the convection that drives R&D tectonics too . Though the latter case requires lubrication which in turn is dependent on starting water mass (- controversial feature for such a planet . Did it form beyond ice line with big water content and avoiding any damaging early stellar activity then migrate in . Did it form close in to where it is now but subsequently get bombarded with icy comets like Earth gravitationally disturbed by nearby Alpha Cent A/B or other planets and also have water, or did it have non to start or get desiccated by the well documented stellar outbursts having formed in situ. )

      In terms of gravitational tides be careful what you ask for. Even in a 1.3Me planet at that semi major axis and they could drive up enough heat to lead to toxic runaway greenhouse in any primary or secondary atmosphere .
      Just so many unknowns to be investigated asap.

      • Michael August 27, 2016, 2:34

        I would expect the tidal forces to be minimal as the planet is most likely tidally locked unless there is eccentricity involved. What worries me and others is the long contraction phase exposing the planet to light fluxes 100’s of times normal for around 50 to 200 million years. The lack of water as Ashley has stated has a crucial effect on starting and maintaining plate tectonics. Now I am not sure if the stellar flux decay is linear or has an exponential rate, if exponential then the total flux exposure will be a lot less and could have prevented a run away greenhouse event limiting water. If there is another super earth or larger planet in an outer orbit it could have thrown in icy material later to water the inner worlds though.

  • Dave Moore August 24, 2016, 18:18

    With a 0.05 AU orbit, there is a very good chance this planet’s orbit will be aligned with Proxima Centuari’s equator. I can’t find Proxima Centauri’s axial inclination in a quick search, but if we knew that then we could get a much more likely figure of the planet’s mass (the sin i in the Msin i).

    • Ashley Baldwin August 26, 2016, 17:31

      It might be aligned with the Star’s equator , indeed likely so at that distance , but that doesn’t necessarily mean that the system’s equator and “plane of the ecliptic ” in turn is inclined at the near 90* to our own system / viewpoint . Only that allows sini to equal 1 and the mass of the planet to be the lowest and also allow potential transits.

    • Harry R Ray August 29, 2016, 20:00

      To transit, though, it would have to be ABSOLUTELY PERFECTLY aligned, because the star is so small.

      • Ashley Baldwin August 31, 2016, 18:37

        It will be if it formed from the same rotating cloud of collapsing interstellar dust as the parent star unless subsequently gravitationally perturbed by say a close pass with Alpha Centauri A/B.

  • DJ Kaplan August 24, 2016, 18:22

    No lie, discovering a planet around our closest star is an exciting scientific acheivement.

    For me, calling something four light-years away “habitable” is something of a stretch when a) we barely know it exists, and b) the only life that we know could possibly be there (at this point), is ourselves, and even that’s a long shot. ;) Yes I do realize that “habitable” is a term of art and is shorthand for certain interesting parameters.

    The scientists from whom I learned, would be interested in finding what’s out there, no matter what it is, rather than what they wish was out there.

  • Rob Henry August 24, 2016, 23:18

    BULLSEYE

    If I wished for a living planet around our closest star, I would put it on the outer edge of the habitable zone (0.05AU) to protect it from atmospheric erosion. I would also give it extra mass to support a denser, and more tightly held atmosphere, but not so heavy that it could not support plate tectonics. Geological heat on its far side would promote the return of volatiles to the near side. About 1.5 times our mass seems right in that optimal zone to maximise that possibility.

    One afterthought is that non-thermal mechanisms of atmospheric erosion are poorly understood, and the effect of flare activity seems speculative to me, as implied by the absence of figures that ever accompany such arguments. It has to be asked: is this really as large a problem as some make out.

  • Rogério Penna August 25, 2016, 0:50

    Before sending Breakthrough Starshot probes to it, send them to the Sun Gravitational Focus so we can directly and perfectly IMAGE this planet.

  • Andrew Palfreyman August 25, 2016, 1:12

    I never thought I’d live to see the day. Just Wow.

    • Andrew Palfreyman August 25, 2016, 3:57

      A couple of comments on points I haven’t yet seen addressed in much detail
      1. Metallicity. Proxima seems to be about the same age as Sol. Can we therefore conclude it’s a Population II type M-dwarf and the 0.21 Fe/H ratio does not cause a problem for putative life?
      2. X- and UV-radiation. In this case, tidal locking is a distinct advantage. It provides a haven from the nasty stuff when needed.

  • xcalibur August 25, 2016, 3:55

    I once commented that if we found a habitable planet around Proxima Centauri, it would be like the universe smiling upon us. I was being rhetorical and hyperbolic, but it’s true – an exo-earth around a nearby star would provide a focus for interstellar efforts, and its existence would suggest that terrestrial planets are common, with many implications.

    And now it seems to be coming to pass. All the data is not yet in, but this is highly encouraging. At the very least, it indicates that there are many worlds like ours, and that a number of them are within reach of a voyage traveling at 90% c.

    Ad astra incrementis.

  • epsilon August 25, 2016, 3:59

    what astounding times we live in!

    I wonder how we can get a fix on the other, still putative, planet in the system…

  • djlactin August 25, 2016, 4:21

    Possible second signal at 30 – 500 days (stated in the text) and at ~ 200 d in the caption to Fig. 2: “Although its nature is unclear, a second signal at P ≈ 200 d was fitted and subtracted from the data to produce this plot and improve visualization.”
    However, this massaging of the data worries me.

    • DJ Kaplan August 25, 2016, 12:54

      You and me both.

      • Harry R Ray September 18, 2016, 16:17

        An ALTERNATIVE EXPLANATION is that Proxima b would have an ECCENTRICITY of 35%, AND; there is ALSO ANOTHER PLANET, but even FARTHER out than 500 days. The reason why they went with their PUBLISHED interpretation, is that this ALTERNATIVE planet SHOULD HAVE TURNED UP IN Endl’s EARLIER data, and it DIDN’T!

  • kzb August 25, 2016, 7:27

    What is the outlook for imaging the posited second planet in its further-out orbit? This should be easier, but is it easier by enough?

  • Frank Smith August 25, 2016, 7:38

    Does anyone know if a strong magnitude field is possible if the planet is tidally locked?

    I would assume a earth-sized rocky planet would have a molten core, but would it move to produce a magnetic field in a tidally locked situation?

    • Karl Zimmerman August 25, 2016, 11:18

      Tidally locked planets still rotate, it’s just that their rotation is either in a 1:1 or 3:2 resonance with their orbit. Mercury still manages a magnetic field around 1.1% of Earth’s strength even though it takes 59 days to rotate. Ganymede is tidally locked with Jupiter with a period of 7 days, 4 hours, but manages a magnetic field three times stronger than Mercury in spite of probably lacking a fully molten iron core.

      The bottom line is Per Ardua would certainly have some sort of magnetic field. Whether one would call it “strong” is another question. Someone with more technical background than I could probably estimate how strong a field would need to be to stop atmospheric stripping and/or dangerous effects of solar flares however.

      • Ashley Baldwin August 26, 2016, 17:37

        You can have 2:1 resonances too and of course unlike Mercury this planet orbits in just 11 days so halve of that is 5 and a half days which isn’t a bad rate . Might yet stir up a magnetic field as might any salty subsurface Ocean created by gravitational tides as with Ganymede.

    • H. Floyd August 25, 2016, 16:36

      Enhancing or engineering magnetospheres seems like essential technology for sustainable off-world habitat building efforts in the foreseeable future, either in this system or at Proxima. In his recent article here, Adam Crowl was confident that magnetospheres can be easily engineered or simulated on other worlds, given sufficiently vast energy resources (a “task… puny by comparison”!). He didn’t elaborate much, but here’s a fascinating discussion vis-a-vis Mars: http://tinyurl.com/zo5q7j8

      Artificial magnetospheres, or maybe more correctly, electrostatic fields constrained by magnetospheres, could provide protection from crippling radiation and atmosphere-stripping solar winds. But for terraforming purposes it doesn’t sound like they’re any substitute for genuine mantle convection, and nice things like crust tectonics, oceans and carbon cycles which would require geodynamics if, as with Mars and Venus, they’re not already present on Proxima b. How to jumpstart a broken planetary engine?

      Alex Tolley, David H and others here finally have me thinking that it’s more feasible to engineer flocks of worldships, and maybe even their inhabitants, than it is to whip hostile planets into friendly dispositions.

      Paul’s “Asteroids as Spacecraft” post in June prompted me to go back and read Rendezvous With Rama from a fresh perspective. Clarke’s hinted-at thesis (spoiler, beware) that spacefaring species will more naturally produce sustainable worldship environments suited to their needs, rather than bothering to conquer and homestead planets foreign to their evolution, suddenly sounds obvious.

      Is preoccupation with planetary homes just another paradigm to outgrow? If so, spacefaring eyes would not be disappointed to find a dead terrestrial planet at Proxima’s goldilocks. It would mean a mother lode of engineering resources, around a new home star with a vastly longer life expectancy than the Sun. Who knows where this discovery will lead? Maybe this means Earth’s last children will live to see her eaten by the Sun, from the safety of Proxima Centauri, and with billions of years to spare.

  • David Payton August 25, 2016, 9:12

    So this brings up a Fermi paradox question…. maybe life around stars like the sun is actually more likely to create a diversity of life that could culminate into intelligent life. Because the radiation is such that the mutations are the right kind and frequency. So alien races do not come here simply for that reason. M dwarf stars being so active might cause too many mutations and never form intelligent life, so more ripe for energy harvesting….

  • ljk August 25, 2016, 9:29

    Here are the links to some papers on the potential habitability of Proxima Centauri B:

    The Habitability of Proxima Centauri b I: Evolutionary Scenarios

    https://arxiv.org/abs/1608.06919

    The habitability of Proxima Centauri b II. Possible climates and Observability

    https://arxiv.org/abs/1608.06827

    The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present

    https://arxiv.org/abs/1608.06813

    Now if only the general media would restrain itself regarding the possibility of life on that exoworld, but I know I am being silly. On the plus side, it may encourage those with the clout and purse strings to push Breakthrough Starshot into reality sooner.

  • Michael C. Fidler August 25, 2016, 9:44

    Could this be a someone sending a signal on 445~GHz from planet Proxima b and what is the black body peak of the red dwarf star Proxima Centauri???
    Submm source within a few arcseconds of α Centauri:
    https://arxiver.wordpress.com/2015/12/10/a-new-submm-source-within-a-few-arcseconds-of-centauri-alma-discovers-the-most-distant-object-of-the-solar-system-ssa/
    https://www.sciencenews.org/article/its-new-planet-its-unknown-star-its-oops

    Interesting!

    • ljk August 26, 2016, 10:10

      First you have to answer the question of why would someone be sending us a signal from that planet? And I have to assume they are not natives to such a world.

      It also seems that the object just happens to be in the vicinity of the Alpha Centauri system from our perspective on Earth, not actually part of it. However this celestial body does warrant further study.

      https://www.centauri-dreams.org/?p=34606

      • Michael C. Fidler August 27, 2016, 9:34

        So what if it is a beacon, and how do we know it a celestial body? The fact is we do not know what it is!

        • ljk August 29, 2016, 12:02

          I asked you first.

  • spaceman August 25, 2016, 10:30

    An amazing breakthrough! The discovery a terrestrial, earth-sized planet in the habitable zone of the nearest M dwarf is truly exciting! Congratulations to all of those whose work led up to this historic moment. It really does not seem all that long ago, at least not to me, when nobody had any firm data on the prevalence of planets around MS stars.

    With a suite of new instruments in development and set to start observing in the next few years, it sure seems like it won’t be more than a decade before we start can really start piecing together spectroscopic data on the planet’s atmosphere (assuming it has one). Exciting times indeed!

  • ljk August 25, 2016, 10:45

    Your comment is awaiting moderation.

    https://arxiv.org/abs/1608.06930

    Biofluorescent Worlds: Biological fluorescence as a temporal biosignature for flare star worlds

    Jack T. O’Malley-James, Lisa Kaltenegger

    (Submitted on 24 Aug 2016)

    Habitability for planets orbiting active stars has been questioned. Especially, planets in the Habitable Zone (HZ) of M-stars, like our closest star Proxima Centauri, experience temporal high-ultraviolet (UV) radiation. The high fraction of M-stars (75%) within the solar neighborhood, the high occurrence rate of rocky planets around M-stars, and the favorable contrast ratio between the star and a potentially habitable rocky planet, makes such planets interesting targets for upcoming observations.

    During M-star flares, the UV flux on a HZ planet can increase by up to two orders of magnitude. High UV radiation is harmful to life and can cause cell and DNA damage. Common UV protection methods (e.g. living underground, or underwater) would make a biosphere harder to detect. However, photoprotective biofluorescence, “up-shifting” UV to longer, safer wavelengths (a proposed UV protection mechanism for some corals), would increase the detectability of biota and even uncover normally hidden biospheres during a flare. Such biofluorescence could be observable as a “temporal biosignature” for planets around UV-active stars.

    We model temporal biofluorescence as a biosignature for an exoplanet biosphere exposed to such conditions, based on planets in M-star HZs. We use fluorescing coral proteins to model biofluorescence, comparing observable spectra, and colors, to vegetation and fluorescent minerals. Our planetary models assume a present-day Earth atmosphere and explore the effect of varying cloud coverage and land:ocean fractions.

    UV flare-induced biofluorescence could be remotely detectable, comparable in strength to vegetation on Earth. On planets in the HZ of M-stars, biofluorescence could be a temporary biosignature, distinguishable from fluorescing minerals and vegetation.

    Comments: Submitted to Ap.J., 16 pages, 10 figures

    Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

    Cite as: arXiv:1608.06930 [astro-ph.EP]
    (or arXiv:1608.06930v1 [astro-ph.EP] for this version)

    Submission history

    From: Jack O’Malley-James [view email]

    [v1] Wed, 24 Aug 2016 19:53:19 GMT (5895kb)

    https://arxiv.org/ftp/arxiv/papers/1608/1608.06930.pdf

  • RobFlores August 25, 2016, 11:09

    For reference Here is a calculation of what it would take in Joules
    to accelerate a one metric ton probe to .25 C (leaving out relativistic effects)

    Delta KE = 1/2 x 1000 x (.25 x 299792458)^2 = 2.8 x 10^18 Joules
    or the energy in a 669 megaton nuclear device. So yes smaller probes
    are more tractable.

    How capable would a 10 kg be if we sent one. My guess is that we will not have the technology within our lifetimes to make this viable.

    However I think we have a shot with a 50kg device in the near term. That is that still means 33 Megatons

    • Robert August 25, 2016, 15:07

      Alternatively, it would take 2.4 years at an acceleration of 1m/s2 using a force of 1000N. Ten Newtons for the 10kg probe. Both require only 1 N/Kg.

      The question is how do we create a constant force without using a monstrous amount of power? Rockets too quickly run out of reaction mass and beams have far too little momentum to transfer.

      • Michael August 26, 2016, 3:09

        Particle beams.

    • Andrew Palfreyman August 26, 2016, 0:20

      Here in a nutshell are some rough numbers for Project StarShot.

      For final coast v=0.2c and an acceleration time of 100 secs, s=3*10^9 m or 0.03 AU. For a 3 m sail, the required best pointing accuracy is 1 nanoradian.
      The acceleration is 6*10^5 m/s^2 or 60 Kgee.
      If the all-up mass is 1 gm, the required force is 600 N. For perfectly reflecting sails, the required beam power is 100 GW.

      • Robert August 26, 2016, 11:42

        If you wish to only accelerate for 100 seconds, have you considered a photon recycling scheme to reduce the required beam power by a few orders of magnitude?

        • Paul Gilster August 26, 2016, 12:47

          This was a topic of discussion at the Starshot meetings I attended this past week. More on that next week.

          • Robert August 26, 2016, 13:05

            Thanks Paul. I’m looking forward to reading that.

      • Robert August 26, 2016, 12:57

        Here’s a question I’ve always wondered. Is it possible to slow light within some gaseous medium and thus increase its momentum? Imagine creating a region around the probe where c=1 m/s and then using a beam where P=E.

  • ljk August 25, 2016, 11:25
  • Tom Mazanec August 25, 2016, 12:19

    I understand this is the same observatory which “discovered” Alpha Centauri Bb.
    I hope this does not turn out to be a mirage like that one.

    • Ashley Baldwin August 26, 2016, 17:50

      Unlikely . The key is the photometry they did at other observatories in parallel with the RV spectroscopy . That ruled out stellar activity occurring at times that planetary “peaks” occurred on HARPS spectrograph which was run over a substantial 80 nights . Effectively excluding any confounders. The signal had been there a while. The lead author told me about the exact figures they ended up publishing last November . But extraordinary claims require extraordinary evidence .

      Nicely covered and imaged on the “lost in transits ” blog run by astronomy doctorate student Hugh Osborn , who is also involved in this line of work with Don Pollaco’s team ( PI for PLATO coincidentally ) . As Hugh says , “they really through the kitchen sink at this”.

  • kzb August 25, 2016, 12:59

    The age of Proxima is now given as 4.85bn years. Not too long ago it was stated the system was 5-6bn years old and significantly older than the sun. Or are they now saying Proxima is younger than Alpha Centauri A and B? Does that mean Proxima is not actually bound to the other two stars?

    • Paul Gilster August 25, 2016, 14:59

      It’s not full determined that Proxima is gravitationally bound to A and B. Current thinking is leaning in that direction, and I’ve written here before about Greg Laughlin’s work on this, but I don’t think it’s completely established yet. Hence there are still questions about Proxima’s age.

    • Lionel Ward August 25, 2016, 17:44

      I haven’t read the research on this, but suspect that gravitational capture of Proxima by Alpha Centauri AB could also have been quite possible – so they could be gravitationally bound yet different in age

    • Ashley Baldwin August 26, 2016, 17:54

      Surprisingly enough given all the research and modern asteroseismology the exact ages of Alpha Centauri A and B ( and with them by default C, on the balance of probabilities as Paul says ) are not well constrained . An age of 4.85 Gyrs is the average , but the range is large , covering from 3.2 Gyrs up to the 5.9 Gyrs you’ve heard !

      • EricSECT August 27, 2016, 6:08

        Ashley:
        Question—(I am no astrophysicist, I only have a basic grasp of the overalls, so bear with me please). The way I understand it, trying to determine an individual star’s age (NOT stars in clusters) is NOT an exact process, surprisingly. Age is more of a guesstimate, primarily based on computer and theoretical models. We apply these models once we know things that CAN be directly measured: For example, the star’s temperature, distance, colour and metallicity (spectrum). And when the models do spit out a number for the probable age of the star, there are large uncertainties. Bottom line: The uncertainties are large because age is a calculated number and cannot be directly measured. Do I have my facts straight?

        If so, this has implications for trying to determine the cause of the dimming at Tabby’s star.

        As an “F” star, Tabby’s lives but a few billion years on the main sequence. But… WHERE on the MS is Tabby’s right now? Is it middle aged (stable) or about to die (unstable)? What are the uncertainties in the age that we calculated for Tabby’s Star? Perhaps we place too much validity on this calculated value of age, when in fact our computer and/or theoretical models may require some tweaking. The star may be just about to exit the MS and hence in an instability region, as we’ve discussed in previous posts (your “overshoots” hypothesis, etc).

        • Ashley Baldwin August 27, 2016, 11:33

          Very good points and a tough question. I think the calculation of for any star is afar less precise process than comes across. I’m no astrophysicist either though stellar development is something I follow closely on arxiv and have read up extensively on asteroseismology which is so critical to exoplanet science . It seems to be improving things significantly but there is a lot to do. Until recently the stars rotation rate was used extensively ( astergyrontology) I.e older stars rotate slower due to magnetic braking , and indeed still is , but there are exceptions and often ages calculated by different methods vary substantially. Alpha Centauri is a real case in point given how it’s average age is given as similar to our own system , but with a big range of values on either side. Even here , stellar activity , which is also used to calculate age , is an unreliable predictor as Proxima is quite active for a star of supposedly billions of years (and a slow rotation rate of 80 plus days -all suggesting a higher age.) . If it was 3.2 billion years that might fit better with its activity but not its slow rotation rate. Hence the need for detailed asteroseismology . Kepler and especially PLATO that is very asteroseismology focused ,will really take things on I’m sure over the next fifteen years. TESS’ relatively short viewing periods will unfortunately limit its effectiveness in this area ( 80 day observations versus up to three years for PLATO)

          In terms of Tabby’s star , . It’s cited as being an F3 star but I’ve seen publications suggesting it is evolving off the main sequence , others that it’s not. So you’re right , I don’t think it’s age has been accurately determined . F dwarfs have very tight spectral lines too apparently which makes assessment and asteroseismology ( including planet hunting) tough . Not that that is ever mentioned when quite precise ages are published for stars!

          In terms of overshoot , this is a well recognised feature of F dwarfs. It’s because of their unique place in the MS ,sitting astride the pp fusion and CNO fusion process interface in their cores that occurs around 1.1-1.2 Msun and particularly the development of core convention at the same point . ( ironically currently a moot point as although listed as a G2 star,Alpha Centauri A shows some evidence of this and it’s listed mass of circa 1.1 Msun is very close to that of a late F star) .

          This can lead to an overshoot of fusion into surrounding non core areas allowing the utilisation of hydrogen that would generally be out of reach ( almost like a smaller version of hydrogen shell burning occurring in red Giants caused as the core runs out of fuel and collapses /compresses heats up and expands) and a sudden brightening presumably followed by dimming .

          I don’t now think overshoot can explain the large 20 % dimming seen in Tabby’s star though . I asked the the Kepler science team themselves to see there explanation . They think it to be due to either the rubble of a broken up planet ( they cited recent observational evidence of planetary remains found around, and inside, some white dwarfs ) which is essentially a variant of the old cometary swarm idea as far as I can see.

          Alternatively they also commented on a similar occurrence they had come across once previously ( but which wasn’t published- as another such system was discovered and written up in the meantime !!) that turned out to be due to a rare quintuple star system consisting if I recall of two binaries and a fifth singular star in a complex orbital dynamic with multiple unpredictable dimming episodes due to eclipses. As contact binaries are the equal biggest cause of false positives with Kepler I think this and the previous white dwarf broken planets theory led to them passing Tabby’s star by. They certainly aren’t over excited about it in discussion !

          Take that his you will. I’m still letting it sink in . I was quite surprised by their comments and relaxed attitude .

          But meantime you are quite right to be wary of the ages cited for individual stars , bar the Sun of course. I was shocked by the 3.2-5.9 range given for Alpha Centauri . When you think how much the Earth ( and maybe Mars and Venus too) has changed over that period. An F3 star can be expected to have a main sequence life of about 2 billion years so for Tabby’s star such variation would have a huge impact on the star’s history too and not just any planets . Stellar Ages need to come with a warning attached for sure !

          • Michael August 28, 2016, 2:15

            ‘If it was 3.2 billion years that might fit better with its activity but not its slow rotation rate. Hence the need for detailed asteroseismology.’

            It still may be a young star (active flares) with the rotation rate brought down by the formation of planets in the system, we have found one there may be many more.

            • Ashley Baldwin August 30, 2016, 8:30

              You never know. Just recently Nasa have revised their opinion on an apparently large red giant star that on closer examination turned out to be a bright protostar despite numerous signs of old age . The key was measuring it’s mass which came out at five hundred Msun. Not even the largest early O stars have that amount of mass and certainly not a red giant with planetary nebula. This is another example of what large surveys turn up . Just wait till Gaia’s finished and we have the LSST up and running. Another reason to be cautious of predictions based on limited data and especially the Sun and it’s system alone . Nothing wrong with that, it’s just that sometimes such predictions are talked about more confidently than warranted which leads to misperception .

        • Ashley Baldwin August 27, 2016, 17:57

          Well worth reading about , F dwarfs . Sato et al have a delightfully well presented and readable summary on them in “habitability around f-type stars ” , arxiv feb 2014.

  • David Cummings August 25, 2016, 13:14

    I am very excited by the prospect of a Starshot launch. I am also confident that long before the probe ever gets there we will have abundant data from new ground and space telescopes, data that will tell us definitively if there is an atmosphere and what that atmosphere holds.

  • DJ Kaplan August 25, 2016, 13:40

    How much light would Proxima receive from α Cen AB?

    • Michael August 27, 2016, 2:43

      Next to nothing, ~100 millionth we would get on Earth, 15 000 AU’s is a long way.

  • Robert August 25, 2016, 13:54

    About the only thing better woud be to find a true earth parallel around Alpha Centauri A or B.

    • DJ Kaplan August 25, 2016, 15:38

      That’s for sure. The apparent angular distance between A and B is at the smallest we will see for the next 80 years, so it’s not really the season for spotting exoplanets in that binary system. :(
      I like to see this Proxima matter as a sort of drill, to get the enthusiasm and funding and instruments in place for the main event. ;)

      However, with A and B getting so close, I wonder if a planet from A could transit in front of B and be spotted?

  • Janw Pool August 25, 2016, 14:35

    Just a thought: what if it is a double planet….? Both rocky and with a slightly lower mass than earth. Does the gravitational pull of Proxima permit two planets circling each other? Or would this have been found in the calculations?

  • RAS August 25, 2016, 14:35

    With this discovery I believe it’s all the more important that we re-study Barnard’s star for comparison not just because it’s also nearby and another Red Dwarf, but at 10 billion years old it must be from at least one generation earlier.

    • ljk August 25, 2016, 15:30

      SolStation is a good source for information about nearby stars, although it does need a little updating in certain places. Here is the entry for Barnard’s Star:

      http://www.solstation.com/stars/barnards.htm

      The Alpha Centauri system, including Proxima Centauri:

      http://www.solstation.com/stars/alp-cent3.htm

      Some day we will colonize Proxima Centauri…. :^)

      http://www.orionsarm.com/eg-article/4ce52fdf5e9de

      …and Barnard’s Star:

      http://www.orionsarm.com/eg-article/4609c8d6cadb4

    • Lionel Ward August 25, 2016, 17:42

      Agree! Also in about 10,000yrs Barnard’s star will be about 3.8Lyr from us, before rapidly receding away – so a much shorter launch window than Alpha and Proxima Centauri

      https://en.wikipedia.org/wiki/Barnard%27s_Star#/media/File:Near-stars-past-future-en.svg

      • RAS August 26, 2016, 2:42

        Thank you for that. Is that a periodic cycling that moving towards us and then away again for our local group of stars & if it is over what period of time does it run?

        • ljk August 26, 2016, 9:04

          Check out this Centauri Dreams article on Erik Anderson’s book Vistas of Many Worlds:

          https://www.centauri-dreams.org/?p=32199

          • RAS August 26, 2016, 13:36

            Thank you for the link. Will have to track down the book mentioned in it.

        • Lionel Ward August 27, 2016, 9:06

          @ RAS
          Sorry for slow reply

          I believe such stellar encounters involve a large amount chance – Wikipedia’s page on Stellar Dynamics says “…stellar dynamical orbits tend to be much more irregular and chaotic than celestial mechanical orbits” due to the endless gravitations tugging back and forth between all these celestial bodies.

          Looking at the bottom two panels of Fig. 1 on http://arxiv.org/pdf/1412.3648v1.pdf it’s clear that stars that we may encounter may have come from and go back to separations of hundreds of light years away

      • Harry R Ray August 26, 2016, 9:47

        And right after THAT comes Gliese 810 to about 1Lyr in about 50,000 years! I know this is VERY long-term planning, but maybe PRD should start FOCUSING on THAT STAR RIGHT NOW(as of yet, NO planets detected, because if there ARE planets there, they all are probably TOO SMALL to detect until ESPRESSO becomes FULLY OPERATIONAL!).

        • DJ Kaplan August 26, 2016, 12:59

          I’m excited to see what ESPRESSO brings as well.

  • Geoffrey Hillend August 25, 2016, 17:01

    Ljk. Brown dwarfs are failed stars of less than seventy six Jupiter masses so there is no light from them at least not enough for life to evolve. There is not enough mass below a certain size to produce a pressure strong enough to start thermonuclear fusion.

    The planets around them would be frozen. There are arguments that life might evolve without light from liquid water in oceans from inner planet heat like Europa around Jupiter etc. but that chances for life are much higher with an Earth like world with Earth like surface conditions and weather such as oceans, liquid water, and light.

    • ljk August 26, 2016, 8:59

      Geoffrey, are you referring to my earlier comment about nearer brown dwarfs with their own planets and rogue exoworlds? I was only pointing out that such objects may exist close to Sol than Proxima Centauri. I was not speculating on whether they could be inhabited or not.

      That being said, while I want to think and say that they probably are not places friendly to organic life, the Universe continues to show just how much it has no interest in limited human knowledge and perceptions on all subjects, including and especially alien life.

  • P August 25, 2016, 20:17

    Perhaps the HARPS Nth and Sth instruments need to embark on a ‘Pale Red Dots’ program – not just Barnard’s Star, but the other close red dwarfs? Who knows what might rise above the noise floor in a concerted campaign? Wolf 359 (an especially faint target for RV, maybe too faint?), Lalande 21185, Luyten 726-8 (also faint), and Ross 154 are all inside 10ly. Finally, Luhman 16 A & B are faint, but maybe not too faint because of their proximity? Wouldnt it be interesting to find small exoplanets around the closest brown dwarfs?

    For me the habitability debates can rage on – I dont really care – I guess the ELTs might sort that out eventually. Its the mere existence of the planets that is so interesting and exciting. What wonderful times we live in.

    P

    P

    P

  • ljk August 26, 2016, 9:13

    New Daily Galaxy article on searching for life on Proxima Centauri b – and other red dwarf systems:

    “Red dwarfs – the dim bulbs of the cosmos – have received scant attention by SETI scientists in the past,” said Jon Richard, of SETI, a private, non-profit organization which stands for Search for Extraterrestrial Intelligence. “That’s because researchers made the seemingly reasonable assumption that other intelligent species would be on planets orbiting stars similar to the sun.”

    Full article here:

    http://www.dailygalaxy.com/my_weblog/2016/08/esos-discovery-of-mystery-planet-orbiting-nearby-red-dwarf-star-proxima-centauri-could-prove-to-be-t.html

    To quote:

    The SETI Institute believes that planetary systems orbiting red dwarfs — dim, long-lived stars that are on average billions of years older than our sun — are worth investigating for signs of advanced extraterrestrial life. The star that’s closest to our sun, Proxima Centauri, is a red dwarf. A variety of observing efforts, including Cornell’s Pale Red Dot initiative, are looking for habitable planets around Proxima Centauri .

    The two-year project involves picking from a list of about 70,000 red dwarfs and scanning 20,000 of the nearest ones, along with the cosmic bodies that circle them using the SETI Institute’s Allen Telescope Array in the High Sierras of northern California, a group of 42 antennas that can observe three stars simultaneously.

    “We’ll scrutinize targeted systems over several frequency bands between 1 and 10 GHz,” said SETI scientist Gerry Harp. “Roughly half of those bands will be at so-called ‘magic frequencies’ — places on the radio dial that are directly related to basic mathematical constants. It’s reasonable to speculate that extraterrestrials trying to attract attention might generate signals at such special frequencies.”