Kepler-186f: Close to Earth Size, in the HZ

by Paul Gilster on April 17, 2014

We have another ‘habitable zone’ planet to talk about today, one not much bigger than the Earth, but it’s probably also time to renew the caveat that using the word ‘habitable’ carries with it no guarantees. The working definition of habitable zone right now is that orbital distance within which liquid water might exist on the surface of a planet. Whether it actually does is just one of the questions. A second is whether or not we’re in fact dealing with a rocky terrestrial world.

So Centauri Dreams approaches the announcement of Kepler-186f with guarded enthusiasm for an exoplanet that looks interesting indeed. Five planets circle this star, an M-dwarf a great deal smaller and cooler than the Sun. Discovered by the Kepler space observatory, the planet presents us with transit information telling us that it is about 1.1 Earth radii, although we don’t yet know what the mass of this world is, and hence can’t make a definitive call on whether or not it is rocky. But Stephen Kane (San Francisco State), one of the researchers involved in today’s announcement, thinks we have reason to think that it is:

“What we’ve learned, just over the past few years, is that there is a definite transition which occurs around about 1.5 Earth radii,” said Kane. “What happens there is that for radii between 1.5 and 2 Earth radii, the planet becomes massive enough that it starts to accumulate a very thick hydrogen and helium atmosphere, so it starts to resemble the gas giants of our solar system rather than anything else that we see as terrestrial.”

Kepler-186f is thus well below the value where we would expect it to accumulate a thick hydrogen and helium envelope, causing Kane to add “there’s a very excellent chance that it does have a rocky surface like the Earth.” If that’s the case, then we have a planet on the outer edge of its star’s habitable zone, though one that may have a somewhat thicker atmosphere than Earth’s because of its somewhat larger size. Perhaps the surface can avoid freezing. In any case, this is what lead author Elisa Quintana (NASA Ames) calls “the first definitive Earth-sized planet found in the habitable zone around another star.” The work appeared today in Science.

quintana4_2

Image: The artist’s concept depicts Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distances from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that Earth-size planets exist in the habitable zone of other stars and signals a significant step closer to finding a world similar to Earth. Credit: NASA Ames/SETI Institute/JPL-Caltech.

The discovery team used so-called ‘speckle imaging’ in obtaining its high resolution observations from the eight-meter Gemini North telescope on Mauna Kea as well as adaptive optics observations from the ten-meter Keck II telescope to rule out extraneous sources that could account for the Kepler data, concluding that the signal has to be that of a transiting planet. The speckle data allowed direct imaging of the system to within 400 million miles, confirming there were no other stellar-sized objects orbiting within this distance from the star. “The Keck and Gemini data are two key pieces of this puzzle,” adds Quintana. “Without these complementary observations we wouldn’t have been able to confirm this Earth-sized planet.”

The new planet orbits its star once every 130 days, receiving about a third of the heat energy that Earth does from the Sun. The four inner planets — Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e — are all too hot for life as we know it, with periods of 3, 7, 13 and 22 days.

quintana

Image: Kepler-186 and the Solar System: The diagram compares the planets of the inner solar system to Kepler-186, a five-planet system about 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 orbit a star classified as a M1 dwarf, measuring half the size and mass of the sun. The Kepler-186 system is home to Kepler-186f, the first validated Earth-size planet orbiting a distant star in the habitable zone—a range of distances from a star where liquid water might pool on the surface of an orbiting planet. Credit: NASA Ames/SETI Institute/JPL-Caltech.

The objection to Kepler-186f as a home for life rests on the dangers of orbiting an M-dwarf, a class of star prone to flare activity. Move a planet close enough to the star to be in its habitable zone and the assumption is that it’s also tidally locked, presenting the same side to the star throughout its orbit, with all the complications that brings to climate models. Neither of these factors are complete show-stoppers — some climate studies show that temperature extremes can be mitigated by winds or ocean currents — and in the case of Kepler-186f, we do have a world on the habitable zone’s outer edge, perhaps far enough out not to suffer tidal lock.

So it’s an interesting place, this new world, about 490 light years away in the constellation Cygnus and thus tantalizingly out of reach for atmospheric analysis even with instrumentation planned for the near future. The James Webb Space Telescope itself won’t be able to help us with that task. But it’s pleasing to note that Kepler-186f has been studied over a frequency range of 1 to 10 GHz looking for emissions, though none has so far been found. Getting a detectable signal here from this star would require a transmitter between 10 and 20 times as powerful as the planetary radar system at Arecibo. SETI keeps coming up empty, but good for us if, in addition to our other studies, we keep our ears open for a long-shot detection.

The paper is Quintana et al., “An Earth-Sized Planet in the Habitable Zone of a Cool Star,” Science Vol 344, No. 6181 (18 April 2014), pp. 277-280 (abstract). This news release from the Gemini and Keck observatories is also helpful, as is this one from San Francisco State University.

tzf_img_post

Wojciech J April 17, 2014 at 14:19

Besides tidal lock, other issues like flares from the red dwarf star would present problems. Nevertheless this is an extremely interesting candidate and hopefully future missions will study its atmosphere.And who knows? Perhaps one day we will have instruments capable of taking photos of the continents and cloud cover.

Harry R Ray April 17, 2014 at 14:19

According to “Planet Hunters”, this planet shows TTV’s. It appears to be in a 10/1 resonance with one of the inner planets. To me,this means that it IS tidally locked, but, if this induces signifigant volcanic activity, the atmosphere should NOT freese out on the permanently dark side. Also, this is a shot in the dark, but I,m sure David Kipping will be looking for a moon around this planet, and if he gets real lucky, he may be able to determine the mass,like he did for the gas midget Kepler138c!

Enzo April 17, 2014 at 16:43

At least this time it looks on the outer edge of the extended HZ that (by comparison with diagram above nearly includes Venus). So maybe it really is in the HZ this time.
When I went through Kepler’s data a while ago, I did notice tat red dwarfs seemed to have more promising planets (in terms of earth size and HZ), even though they were only of small portion of the stars observed.

coolstar April 17, 2014 at 16:45

The orbital period of planet f is close to 10x that of planet d, which also has the largest size of the planets detected at about 1.4 R(earth). that doesn’t necessitate that planet f is tidally locked to the star though. But it does mean that further constraints on the masses may be forthcoming.
A significant omission both from the paper in Science and the press conference is exactly what the radial velocity amplitude would be for planet f. given estimates of its mass. If you plug in the best numbers for the mass of the central star, the period of f, assume a circular orbit, and an inclination of 90 degress (all reasonable estimates), then the rv amplitude scales as
7.26 cm/sec times the mass of the planet in earth masses.
That should be detectable with the next generation of rv spectrograph on the EELT. The star isn’t THAT faint, at 14 mag, it’s chromospherically quiet with a rotation period of about 34 days and no large flares have been observed. Long integration times can be used to average over p-mode oscillations and the orbital period of the planet isn’t (quite!) an integer multiple of the rotation period so any necessary corrections for activity on the star should be doable. It would be nice to know the rotational amplitude of the light curve from the Kepler data to get a better idea of magnitude of the corrections though.

Dave Moore April 17, 2014 at 16:49

Does anybody know the eccentricity of this planet’s orbit?

tesh April 17, 2014 at 17:03

Wonder why there is a big gap between the inner system and the outer planet?

Holger April 17, 2014 at 17:12

Enzo:
“At least this time it looks on the outer edge of the extended HZ that (by comparison with diagram above nearly includes Venus). So maybe it really is in the HZ this time.”

I don’t understand what you mean by this. 186f gets less solar irradiation than Mars does (the published image deceivingly doesn’t show the whole extent of the “comparison” habitable zone around Sun). That’s not very promising to me, it may well turn out to be too cold, just like previous Kepler planets did turn out to be too hot.

It’s strange that the first discovered Earth-sized planet in the HZ lies at its outer edge – closer Earth analogues should have been more easy to discover due to lower orbital period. Therefore it seems that none of Kepler’s observed M-dwarfs has a transiting Earth-mass planet with warmer “habitable” temperatures…

Brett April 17, 2014 at 23:36

I wonder if that would be so far out in terms of sunlight that CO2 would freeze out of the atmosphere as opposed to staying as a gas and warming the planet (methane could still stay up if there’s a reliable source). That already happens on Mars during the southern hemisphere’s winter.

Andrew Palfreyman April 18, 2014 at 4:06

What makes April 17th 2014 a red letter day in human history for me is the demonstration afforded by Kepler 186f that M-dwarves can support a planet that is potentially life-bearing, and that such stars are ubiquitous. To quote a news source I read today
“The good news is that there are ridiculous numbers of M-dwarfs in the Milky Way—far more than there are Sun-like stars. There are so many, in fact, that a study concluded last year that if only six percent of them had an Earthlike planet, and if they were spread evenly through the galaxy, that would put the nearest one a mere 13 light-years away. “

Enzo April 18, 2014 at 7:56

@Holger,

What I meant is that, so far, planets declared to be in the HZ have often been well inside the equivalent of 0.95-0.98 AU. That’s because there’s been a tendency of extending the HZ nearly to Mercury’s orbit in order to announce planets in the HZ.
So, I was hoping that this time, even taking into account this common exaggerations, the planet is REALLY in the HZ :-)

Personally, I’d rather see planets on the outer edges of the HZ than the inner edge. The reason is the possible atmosphere. Earth has a very thin atmosphere compared to what earth mass planets are capable of (see Venus and Kepler 138c the gas dwarf).
Therefore I’m more worried that thicker atmospheres then Earth’s might be more common on Earth mass planets and, hence, being further out is better.
I don’t have any evidence for this, just a bit of extrapolation on the little we know.
If Earth is really that close to the edge of the HZ as multiple studies suggest, than a few extra bars of atmosphere could be all it’s needed to make it (or another world in a similar position) inhabitable.

Brett Bellmore April 18, 2014 at 8:48

About 500 light years; I’d expect that, by the time we get that far from Earth in our colonization efforts, we’ll have the tech to live just about anywhere there’s energy and matter.

This planet might be a good candidate for terraforming, being tidally locked at the outer edge of the HZ; You could put a good sized mirror at L-2, and illuminate the back side at whatever level was desirable, and not concern yourself with the flares bombarding the day side.

Harry R Ray April 18, 2014 at 9:52

This is an UPDATE on my ORIGINAL comment. A COMPANION paper to the discovery paper just showed up on ArXiv! Eliza Quintana was a participant, but the lead auther was Sean Raymond, also of the Seti Institute. Kepler 186 most likely has 2 MORE non-transiting (this is NOT a CERTAINTY) planets in the gap between e and f! The good news is that the best fit to f<s TTV"s is either a super earth in a 2/1 or 3/2 resonance with f, which would mean that it would be in the warmer part of the hz! The bad news is that this would COMPLETELY STYMIE David Kipping's potential determination of 's mass(see my EARLIER comment)! ALSO: Raymond appears to believe that f is LESS than 10% larger yhanearth, making it EVEN MORE of a "twin" of Earth! Abel Mendez's HEC lists it at ONLY 1.02 Earth radii!

Ronald April 18, 2014 at 12:08

Although any discovery like this is fascinating and important in it own right, I am not overly impressed. What makes this discovery special is the fact that is has been confirmed by ground observatories.
But apart from the fact that its mother star is an M-dwarf, with the risk of flares and tidal locking, 186f receives 1/3 of Earth’s insolation: this corresponds with about 1.7 – 1.8 AU in our solar system, well beyond Mars and barely or not in the HZ.

There are much better Kepler candidates even now, just not confirmed yet, which takes time.
As I reported recently, I found at least 5 very good earthlike candidates around solar type stars in the Kepler (KOI) database at Caltech:
ID/Name Temp Lum Mass Radius Metal ID/Name Radius AU Mass (Me) ESI (PHL) PHL designation
5091808 5786 0,69 – 0,83 -0,82 K05123.01 1,09 0,77 – 0,93 G-Warm Terran
11654039 5997 1,09 – 0,97 -0,14 K05927.01 1,24 1,13 – 0,91 G-Warm Terran
8570210 5829 0,67 – 0,8 -0,42 K05545.01 1,05 1,25 – 0,72 G-Warm Terran
11465869 5359 0,53 – 0,74 -0,28 K05904.01 0,77 0,86 – 0,82 G-Warm Subterran
10663976 5513 0,44 – 0,73 -0,46 K05819.01 1,29 0,95 – 0,83 G-Warm Superterran

(I hope the table comes out well)

They are also mentioned in the PHL data, as well as the new 186f:
http://phl.upr.edu/projects/habitable-exoplanets-catalog/data

RobFlores April 18, 2014 at 12:12

As pessimistic as I have been regarding Twin earth finds:

I think we will find an ideal world to colonize much closer than 500LY.
At 100-250Ly the number of K and G, and Lower Mass F, stars are pretty
large. Odds favor One really good Twin of Earth*. This assumes there
in not an undiscovered mechanism that inhibits the creation of Earth
sized planets around the HZ’s of those type Stars.

* Large moon sold separately
(too unlikely an event to be
common around terrestrial planets.)

Ronald April 18, 2014 at 12:18

For clarity:
The 1st column is the Kepler star ID, 2nd column Temp (in K), 3rd column Luminosity (*solar), 4th column stellar mass (all empty, dashes –), 5th column stellar radius (* solar), 6th column metallicity, 7th column planet (KOI) ID, 8th column planet radius (* Earth), 9th column planet S.M. axis (AU), 10th column planet mass (all empty, dashes –), 11th column Earth Similarity Index (by PHL), 12th column PHL designation of planet type.

ljk April 18, 2014 at 12:46

Has anyone heard of the SETI detection around TYC 1220-91-1 before?

Here is where I just learned about it:

http://infidel753.blogspot.com/2014/03/the-blip.html

There are images and other data here, including a link to the science paper on the event:

http://www.abovetopsecret.com/forum/thread1000282/pg1

http://arxiv.org/ftp/arxiv/papers/1211/1211.6470.pdf

Worthy of more investigation and discussion, I would say.

andy April 18, 2014 at 13:44

While 1/3 Earth insolation is indeed less than present-day Mars, it is a pretty good match to Mars under the ZAMS Sun, which is the time that the evidence suggests Mars had liquid water at its surface.

It’s also not entirely clear that the planet would actually be tidally locked, depending on various (unknown) parameters such as tidal dissipation rate it may not be, and depending on what planets (if any) are in the gap between “e” and “f” it may even maintain a significant obliquity. See today’s arXiv paper Bolmont et al. “Formation, tidal evolution and habitability of the Kepler-186 system.”

Peter Popov April 18, 2014 at 19:08

Kepler can detect planets whose orbits lie in a plane aligned with our line of sight. This means about 1% of all planets are detectable by this method. 186f is the first detected earth-sized habitable planet at 500ly distance from here. Therefore, a lower estimate on the number of earth-sized habitable planets within 500ly is 100. Assuming random distribution, this means the closest is 500/(100^(1/3)) ~ 107 ly. This is a lower estimate.

So, how to design a starship that can transport a human within reasonable time @ 100ly, assuming non new physics?

coacervate April 18, 2014 at 20:30

A thick atmosphere and magnetic field might protect against flares. Also if it is tidally locked doesn’t that leave a band around the terminator where things would be blissful?

Paul, shouldn’t you write this story if someone has not already? And really hoping to see your book on “AC: current knowledge and conjecture” on Amazon soon.

Tish, i think mars is cold because its blanket of co2 is too thin.

I can’t help but hope we can somehow expand our range to these sorts of distances, as I’m sure we all do. Being a non-physicist, I am free to dream of stargates or other loopholes in the lightspeed limit. Someday…someday. Thanks for this great blog. Such a welcomed Oasis amidst the endless parsecs!

Joe April 18, 2014 at 21:33

What I find amazing about the coverage of Kepler 186F is that most newscasts failed to mention that the image of the planet is just an artist’s rendition. A lot of people seem to think this is an actual photograph of the planet. And while I’m sure the artist’s work is original, the image looks a lot like SF paintings of Dune or Tatooine.

ljk April 18, 2014 at 21:47

Five points to make about this new exoplanet find:

http://www.space.com/25541-alien-planet-kepler-186f-facts.html

Peter Popov said on April 18, 2014 at 19:08:

“So, how to design a starship that can transport a human within reasonable time @ 100ly, assuming non new physics?”

How about we build an interstellar vessel that can get us to Alpha Centauri in a reasonable time period first before we go hundreds of light years? We are still quite far from that relatively modest proposal.

P April 18, 2014 at 23:25

A lot of people seem to forget that Mars is actually in (just) the Sun’s Hz. Mars’ problem is not its position(it might actually be in a better position than the Earth re the long term evolution of the Sun) but its size. Its just too small.

P

Michael April 19, 2014 at 1:33

@andy April 18, 2014 at 13:44

‘It’s also not entirely clear that the planet would actually be tidally locked…’

My biggest concern with tidal locking of a planet is the loss or reduced likelihood of a magnetic dynamo, a protective field. If there is no magnetic field and the star is flaring UV there is an increased likelihood of the atmosphere been removed. Also living at the terminator on a tidally locked planet reduces the effects of UV by the atmosphere been optically thicker. The winds though must be fast due to the large differences in temperature between the light and dark sides.

@Peter Popov April 18, 2014 at 19:08

‘So, how to design a starship that can transport a human within reasonable time @ 100ly, assuming non new physics?’

I am not sure we would want to go there in person anyway, we can study the planet from afar. If the planet is inhabited our biology and bacterial cohabitates may not be compatible with theirs.

Brett Bellmore April 19, 2014 at 7:47

In one trip? Define “reasonable time”. I would be surprised at a technology which could drive a starship, (rather than a “probe”) to greater than 20% of C. So, neglecting for acceleration on both ends, 500 years. That’s either a generation ship, suspended animation, or radical life extension.

I think, barring some radical development, we will need to make that trip in shorter hops, with colonies in between. This implies that the colonies will NOT be at sites with remotely habitable planets. We’ll have to learn to live in space as a destination, not just as a route.

But, playing the game: The only propulsion technology I’m aware of that uses current physics, capable of reaching near-relativistic speeds, is some form of beamed propulsion. EM radiation, or my favorite, the mass beam. The real limit with this sort of propulsion becomes your technology for surviving the interstellar media, because it circumvents the mass ratio issue.

Then you “just” need to slow down at the other end of the trip. Perhaps some combination of Magsail and fusion or anti-matter rocket?

But I don’t see that being applied to such long trips; The further you go, the greater the odds for some accident along the way.

Holger April 19, 2014 at 16:15

@Enzo:
Thanks for explaining your argument.
But not all previous HZ discoveries were close to the inner edge; e.g. Kepler-62f is in a similar position as 186f according to this beautiful overview: http://www.nasa.gov/sites/default/files/hz-tempstellar-flux_victoria_meadows.jpg

I agree that an “average” Earth-sized HZ planet may have a denser atmosphere than Earth, but I don’t see a much denser atmosphere as something positive for habitability: Venus’ atmosphere is believed to be a result of its being too close to the Sun (evaporation of presumed water oceans led to large amounts of CO2 via loss of hydrogen) and of its lack of plate tectonics; a “super-Mars” would keep its water on the ground (like Earth did) and not produce a CO2 atmosphere that it would need to keep the water liquid.
And I don’t know if an H/He atmosphere does increase surface temperatures, but a gas dwarf like 138c would be expected to be uninhabitable anyway AFAIK.

Peter Popov April 19, 2014 at 16:24

Interesting comments. The 107ly estimate is the most pessimistic one. It is related to what is observable by the current technology, the amount of data that has been processed and confirmed, and a few radically uncheckable statistical assumptions. The main benefit of the Kepler spacecraft is that it allows us to gather sufficient data so one can use statistics in a meaningful way. If this particular planet is habitable or not wil not be known for a very long time to come.

@Brett: yep, progresive collonization. By the time we get to 100ly, planets probably won’t matter as we’ll be used to space.

@ljk the question was just a teaser. Clearly we need to settle the solar system first, then travel to the nearby stars … I was just hapy I could come up with an upper bound estimate on the distance to closest habitable planet.
going to bed

Holger April 19, 2014 at 17:08

@Peter Popov:
“Kepler can detect planets whose orbits lie in a plane aligned with our line of sight. This means about 1% of all planets are detectable by this method. 186f is the first detected earth-sized habitable planet at 500ly distance from here. Therefore, a lower estimate on the number of earth-sized habitable planets within 500ly is 100. Assuming random distribution, this means the closest is 500/(100^(1/3)) ~ 107 ly. This is a lower estimate.”

That calculation makes no sense to me: the 500 ly distance of this planet is completely unrelated to the distance of the nearest HZ world – Kepler does NOT look at all stars within 500 ly (almost all of its target stars lie much further away). Also, “habitable zone” does not imply a habitable planet, as noted in the article.
FWIW, where did you get the “1%” transit probability? I’d expect the probability of an Earth analogue’s transit to be higher than that for red dwarfs…

Enzo April 19, 2014 at 17:13

@Holger,

Yes, I previously posted that Kepler 62f was the most promising so far.

” I don’t see a much denser atmosphere as something positive for habitability”

Neither do I. And that’s why I said that, since I expect it to be denser, I’d rather see more planets away from the edge of HZ in order to increase their chances of being habitable.
Ronald’s table looks good.

BTW, H/HE does work as greenhouse gas and moves the HZ outwards :
http://geosci.uchicago.edu/~rtp1/papers/H2Worlds.pdf

Nathan Currier April 19, 2014 at 20:13

ljk:

Thanks for those links. Hadn’t heard about this signal before. I’m surprised it only got a few pages of Google hits, all from alternative websites.

Hydrogen times pi. That was the frequency of the signal from the movie Contact. Interesting coincidence (if it is a coincidence). Also, Jill Tarter is on the paper, probably as tribute for running SETI. Jill Tarter was the inspiration for Jodie Foster’s character, Ellie Arroway.

Actually, it’s not quite hydrogen times pi. It might be if it were Doppler shifted by a radial velocity of -106km/s. That’s very high but still possible.

Due to lack of interest, we might have to wait for the GAIA mission to tell us the radial velocity of TYC 1220-91-1. We would also need to know the time the signal was detected, to correct for Earth’s motion. Haven’t been able to find this time anywhere.

Brett Bellmore April 20, 2014 at 7:17

“By the time we get to 100ly, planets probably won’t matter as we’ll be used to space.”

By the time we launch the first starship, more realistically. No planet bound species is going to master the necessary technologies. Reaction drives with exhausts powerful enough to fry a planet? A species that runs screaming from radiation levels that don’t even have biological significance isn’t going to build those.

No, we’ll move into space, and then the people living in space will launch the starships, likely over the futile protests of the planet bound. But they’ll have gotten used to ignoring those protests, from using nuclear bombs to push asteroids around.

Wojciech J April 20, 2014 at 10:27

To all the people talking about colonizing or terraforming this planet. If you have a technology to transport people 500 light years and keep them alive in artificial habitat, you no longer need to colonize other planets. I repeated this before, but I think it is important point. You either can create artificial habitats with perfect living conditions(much more faster and efficiently than a planet will be terraformed) or you have post-biological population which needs no planets to exist.
And of course if there is an alien biosphere it is far more valuable for study and research than colonization.

Brett Bellmore April 20, 2014 at 20:05

I think there’s a fair excuse for terraforming a planet, if a suitable one is at hand: While not an efficient use of the mass, habitable planets are very long lasting habitats for life.

We have, today, one example of intelligent life, and that life evolved on a planet over a long period of time. That planet has sustained life for billions of years.

It would be folly to assume that a technological civilization in space, dependent on technology for it’s survival, would be this reliable. (Though it certainly might be.) Why not take the chance to create a second cradle of life, complex life, to reseed the galaxy if our space borne technological society falls?

andy April 21, 2014 at 7:42

To all the people talking about colonizing or terraforming this planet. If you have a technology to transport people 500 light years and keep them alive in artificial habitat, you no longer need to colonize other planets.

Rubbish. It’s perfectly possible to envisage scenarios where this is not the case, e.g. if human hibernation becomes possible — the requirements of keeping people in hibernation would presumably be rather different to keeping them alive.

The view that planets become irrelevant when living in space becomes possible utterly ignores that a planetary environment gives you a massive buffer against the fact that it is impossible to build a truly closed system. A space habitat by contrast is going to be far more vulnerable to the various losses due to inefficiencies in the recycling processes, etc.

Furthermore, we’re already running up against the limitations of our own planet to provide a buffer against the various byproducts of human technology: anthropogenic climate change shows us that there’s only so far we can push the system before it has measurable consequences. Since we’re failing at managing such a system, I do not have much hope for our capability to handle a much less forgiving and stable scenario such as a space habitat.

Michael April 21, 2014 at 10:35

@Wojciech J April 20, 2014 at 10:27

‘To all the people talking about colonizing or terraforming this planet. If you have a technology to transport people 500 light years and keep them alive in artificial habitat, you no longer need to colonize other planets.’

I agree, making an artificial habitat will be a lot easier than terra-formation. However worlds could be utilised if say they are close to tipping towards a habitable world like ours, it would just depend on the resources needed.

‘And of course if there is an alien biosphere it is far more valuable for study and research than colonization.’

Again I agree on this point as well, unless our biology, including our bacterial baggage, were compatible it would be folly for us and the indigenous inhabitants to physically interact.

@andy April 21, 2014 at 7:42

‘A space habitat by contrast is going to be far more vulnerable to the various losses due to inefficiencies in the recycling processes, etc.’

If we can travel 500 lyr then we will have the tech to manage a closed system for long term durability I would think.

Michael April 21, 2014 at 13:46

@ljk April 18, 2014 at 12:46

‘Has anyone heard of the SETI detection around TYC 1220-91-1 before?’

This did not make the big news in any way so I looked a little deeper. I still remember that incident when they thought they had a transmission but the guy who was on duty kept missing it, it turned out to be when he used the microwave for his dinner!

Unfortunately there is no radial velocity information about the Star. We do have a proper motion though of {13.2 -19.2} which translates to ~23.3 mas/yr. (SIMBAD)

When we work out the transverse velocity we get about ~159 km/s. So because it is so large it is less likely to be coming towards or away from us. So a Doppler velocity of around 106 km/s is harder to get but not unreasonable.

As for a long duration alien transmission I think it would unwise of them energy wise, best transmit a signal to the most likely stars for a while then to the next, say changing the frequency in prime numbers. So if we next see it and it is 5 times the hydrogen emission then it more likely an ‘alien’ transmission. My thoughts are also pulled to the doppler shift if its was a hydrogen emission line as we don’t have any spacecraft flying around at that speed. Further we have only been transmitting radio waves for about a century so they may have just got the signals, but it would take another 100 years to respond.

I can’t seem to get any info on the pulses so more than likely a reflected earth transmission, probably the neighbours stereo.

Michael April 21, 2014 at 14:27

It looks very much like the signal from the Crab nebulae.

crab

05 34 32 +22 00 52 pulsar 4462 Mhz 2010-05-07

Very strange object (1 of a kind) has short giant pulses, 4462.336 MHz

And here

gal anti-center

05 45 37 +28 56 10 Galactic Anti-center 4462 2010-05-07
Taken at the “magic” PiHI frequency = 4462.336 MHz, a clean band

And the famous WOW signal

WoW1

19 25 31 -26 57 00 legend 1430 Mhz 2011-02-18

Position of the famous Wow! signal[9]

PiHI looks quite common

http://setiquest.org/wiki/index.php/SetiQuest_Data_Links

Most likely a false alarm, phew I can sleep easy

Eldritch April 21, 2014 at 23:30

“Getting a detectable signal here from this star would require a transmitter between 10 and 20 times as powerful as the planetary radar system at Arecibo. ”

Could you explain how this was worked out? Other sources I’ve found say we could detect a radar system as powerful as Arecibo from 720 ly (if we were also recieving it with Arecibo). Are you just assuming a less effective reciever on our end?

Paul Gilster April 22, 2014 at 8:52

Eldritch, the figures come from the SETI Institute, so I’d send you to them for how the calculation was worked out. You can see them cited in this news release:

http://www.seti.org/seti-institute/press-release/press-release-first-discovery-earth-sized-planet-habitable-zone

ljk April 22, 2014 at 11:19

Interesting new cosmic radio bursts from much farther out:

http://io9.com/unexplained-intergalactic-radio-bursts-confirmed-at-ari-1565649619

Imagine Kardashev Type 3 civilizations trying to get in touch with other similar types in neighboring galaxies. To make a K Type 4 perhaps? Or just that conversing with anything lower on the scale is so boring.

Michael April 22, 2014 at 12:54

There is every reason to suggest that the planet has a thick atmosphere. If you look at Venus, CO2 aside it has around 2-3 bars of nitrogen. Earth could quite possibility have lost the rest of its nitrogen thru the moons formation process. CO2 in the presence of water would not last billions of years in a planets atmosphere, it would form carbonates at the surface. But with only the same amount of energy falling on it as mars it may well still be a frozen world.

snippet

https://www.ncbi.nlm.nih.gov/m/pubmed/23855332/?i=8&from=/23537135/related

‘..Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant.’

I wonder if this is why our early earth did not freeze over, our sun outputted more in the red part of the spectrum during its youth which is less reflective in the infrared part of the spectrum.

see full article

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3746291/

Ronald April 23, 2014 at 5:27

andy:
“The view that planets become irrelevant when living in space becomes possible utterly ignores that a planetary environment gives you a massive buffer against the fact that it is impossible to build a truly closed system. A space habitat by contrast is going to be far more vulnerable to the various losses due to inefficiencies in the recycling processes, etc.”

One of the very best things I have ever read here, and something I have argued myself many times over. Space colonies are intrinsically instable and vulnerable and require continuous intensive maintenance and rebuilding, planets are intrinsically long-term stable (as in: surviving changes) objects.

Michael: “If we can travel 500 lyr then we will have the tech to manage a closed system for long term durability I would think.”
If superman existed, he could certainly fly. I sincerely hope and expect that the nearest suitable (as in: either habitable or easily terraformable) planet is much, much closer than that, I would rather think a few tens of ly.
And: surviving in a state of deep hibernation in order to be revived upon arrival, much like a seed, is not exactly the same as *living* in a closed ecosystem.

Michael April 24, 2014 at 9:47

@Ronald April 23, 2014 at 5:27

‘andy:
“The view that planets become irrelevant when living in space becomes possible utterly ignores that a planetary environment gives you a massive buffer against the fact that it is impossible to build a truly closed system. A space habitat by contrast is going to be far more vulnerable to the various losses due to inefficiencies in the recycling processes, etc.”

You can build very large rotational colonies so you can incorporate a lot of redundancy in it.

‘Space colonies are intrinsically instable and vulnerable and require continuous intensive maintenance and rebuilding..’

They may be a little vulnerable to space weathering but they are not unstable or require intensive maintenance and rebuilding. There are plenty of techniques that could be used to protect it.

‘I sincerely hope and expect that the nearest suitable (as in: either habitable or easily terraformable) planet is much, much closer than that, I would rather think a few tens of ly.’

The problem with habitable, in an earth sense, is that it will most likey have a biological eco-system in place that we would not know the consquences of interferring with, we could wipe it out by accident!

Robert Feyerharm April 24, 2014 at 13:22

Michael – thank you for the article link discussing CO2 levels and stellar luminosity (or “instellation” – different from luminosity?).

Leaving the effects of different stellar spectrums aside, if you slide an Earth sized planet outwards towards the outer edge of the HZ, presumably you can increase the bars of CO2 to maintain surface habitability. CO2 seems to have been an abundant atmospheric ingredient in the solar nebula. But at what point does this model no longer work? I suspect the greenhouse effect of CO2 cannot completely compensate for less solar radiation at some distance, no matter how many bars of CO2 you pile on, although this may require a sophisticated mathematical model to prove.

Michael April 25, 2014 at 3:12

@Robert Feyerharm April 24, 2014 at 13:22

‘Leaving the effects of different stellar spectrums aside, if you slide an Earth sized planet outwards towards the outer edge of the HZ, presumably you can increase the bars of CO2 to maintain surface habitability. But at what point does this model no longer work? I suspect the greenhouse effect of CO2 cannot completely compensate for less solar radiation at some distance, no matter how many bars of CO2 you pile on, although this may require a sophisticated mathematical model to prove.’

I can’t see large amounts CO2 been in a cool enough planets atmosphere over billions of years especially where there is abundant water, carbonates would form. I also see too much CO2 as although beneficial to habitabilty in keeping the place warm to much would prevent animals from breathing effectivily and would tend to form an acidic ocean. As for a very thick CO2 atmosphere if say the planet formed in the outer reaches of the HZ and had a warm temperature profile it would eventually get colder and colder as the CO2 was removed from the atmosphere and sequestered.

Ashley Baldwin April 28, 2014 at 15:44

Very good point Michael. Eventually , Greenhouse or not the stellar flux per unit planetary surface drops too low and the CO2 freezes out and the system collapses. This has been used as one of the definitions of the outer limit of the Habitable zone .
The other key to M dwarf habitability of course is tidal locking. If you google this with ” graph” you will find a nice graph charting the “high tide” line for tidal locking per spectral class . Although this graph is crude , it shows that for a semi major axis of about 0.4 AU , Kepler 186 f will remain outside of the tidal locking zone for a long time ( the graph does not show that time is also involved in tidal locking but that complicates what us a nice visual demonstration unnecessarily) , hopefully long enough for life to develop without being subject to a permanent night/day cycle. Kepler 186 is a large M dwarf , approaching the maximum mass for the class of 0.5 M sun, so its habitable zone extends about as far as an M dwarf’s can ,although a thick greenhouse atmosphere ( perhaps from a large , volcanically active planet) with high obliquity to help prevent glaciation should mitigate and drive it out further . The further the better , as apart from tidal locking , it will help keep ‘f’ as far as possible from those nasty CME, XUV and X rays we all know M stars are capable of .( some evidence suggests that even 0.8 AU isn’t enough for even the strongest dynamo induced magnetic field to hang onto an atmosphere , so hence the need for ongoing volcanic activity to keep belching out fumes) .

Michael April 29, 2014 at 0:00

@Ashley Baldwin April 28, 2014 at 15:44

‘Greenhouse or not the stellar flux per unit planetary surface drops too low and the CO2 freezes out and the system collapses. This has been used as one of the definitions of the outer limit of the Habitable zone .’

Yes, High pressure gases would also have a direct impact on life’s biomechanics through protein folding issues and molecular cellular transfer mechanisms. Could hydrogen under high pressure cause proton pump issues? I would think so. So a greenhouse effect based on hydrogen could also causes issues, but it is unlikely with helium. Once you start applying all these filters or stressors we can start to see why life could be so rare.

‘Although this graph is crude , it shows that for a semi major axis of about 0.4 AU , Kepler 186 f will remain outside of the tidal locking zone for a long time ‘

The greater the eccentricity the greater the chance of a resonance rotation and liberation so the chances of tidal locking could be reduced.

‘hopefully long enough for life to develop without being subject to a permanent night/day cycle.’

There is the terminator around the planet which would be quite large and the denser the atmosphere the greater light will be bent around it creating a wider twilight zone of hundreds of kilometres. At the terminator the optical thickness is also very high giving more protection against the stars tantrums.

‘…volcanically active planet) with high obliquity to help prevent glaciation should mitigate and drive it out further.’

Although volcanism could help it too eventually subsides. The dynamo issue is of greatest concern, any tidally locked planet runs that risk. My opinion is that a higher gravity world and thicker atmosphere, but not to thick, are required to aid life on planets around Red dwarfs against the Stars volatilities.

ljk May 28, 2014 at 9:50

Looking for signs of life on Kepler 186-F

May 19, 2014

By Gerry Harp, Director of Center for SETI Research

Consider this post, which firmly states that proto-Earth Kepler 186-f has a 50% chance of harboring technologically equipped intelligent life:

http://www.science20.com/quantum_gravity/blog/a_better_than_5050_chance_kepler186f_has_technological_life-134555

Although about science, this blog is primarily lacking in real science. By my reckoning, even the most optimistic assumptions indicate a probability of <4 GHz, because signals sent continuously may still fade in and out over time due to scattering from interstellar gas on the way to Earth. Multiple observations increase the likelihood that our telescope will detect the signal.

Simply put, if about 500 years ago, 186-f were transmitting a tuning-fork like radio beacon, then we would have seen it. Provided their transmitter were at least 8x as powerful as the most powerful transmitter on Earth, the Arecibo planetary radar. Considering that ET probably has better technology than humans do (since we are a very young technological civilization), this is far from impossible.

Each day, the signal reports came in, but there was no evidence of alien signals. We celebrated on the day that we finished the first complete scan 1-9 GHz of the planet. Even though we didn’t find ET, we knew that we could support Quintana’s discovery by helping to answer the obvious question, “So you’ve discovered an Earth-like planet, do you think it bears life?” By the time Kepler 186-f was published by Science, and the embargo was lifted, we had a very good sample including 2-3 scans over the planet. Whew! That was fun!

It is important to note that our SETI measurements do not prove there is no intelligent life on Kepler 186-f. If 186-f has intelligent life, then they might be sending signals weaker than we can detect, or they might be sending signals in the visible (optical) domain, or perhaps not at all in the direction of Earth. Future research may find signals we missed.

Kepler 186-f is just the first of uncountable planets that could harbor life “as we know it.” Extrapolations of Kepler results suggest that Earth-like planets are abundant. Still, life as we know continues to be evasive. As Fermi put it, “Where are they?”

This article first appeared on the Cosmic Diary blog.

ljk May 28, 2014 at 9:53

Somehow the previous article messed up. Here is the proper link to the whole piece:

http://www.seti.org/seti-institute/news/looking-signs-life-kepler-186-f

Simply put, the discoverers of Kepler-186f contacted The SETI Institute just before its public announcement and asked them to aim the ATA at the exoplanet to see if any artificial signals could be detected over a few days.

Shockingly, none were.

ljk June 25, 2014 at 11:26

Abundance of Earth Analogs

Drew Ex Machina

By Andrew Lepage

June 25, 2014

The original motivation behind NASA’s Kepler mission (and, indeed, the primary driver of the design of its hardware) was to detect Earth-size planets orbiting Sun-like stars in Earth-like orbits. While the ongoing analysis of the huge amount of data from Kepler’s primary mission has uncovered thousands of planets to date including easier-to-detect Earth-size planets in short-period orbits, larger planets in Earth-like orbits and even potentially habitable planets orbiting stars much smaller than the Sun, no true Earth analogs have been found… yet!

This is not to say that such planets do not exist. They are just more difficult to detect via the transit method than those already announced and will require more time to tease out of the data set from Kepler’s prime mission.

Full article here:

http://www.drewexmachina.com/2014/06/25/abundance-of-earth-analogs/

ljk July 9, 2014 at 11:04

Astronomers Discover First Ever Terrestrial Exoplanet in Earth-Type Orbit, Around Red Dwarf Binary Star System

By Leonidas Papadopoulos

An artist’s rendering of the newly discovered exoplanet OGLE-2013-BLG-0341LBb (far right) orbiting one star (right) of a binary red dwarf star system, from an Earth-type distance of approximately 0.9 Astronomical Units away. Image Credit: Cheongho Han, Chungbuk National University, Republic of Korea

The discovery of yet another exoplanet orbiting outside of the habitable zone of its star hardly seems newsworthy these days, given the routine nature of new exoplanet findings. Having already discovered thousands of alien worlds within the Milky Way galaxy showcasing a huge diversity in mass, size, orbital characteristics, and possible habitability, astronomers are now focused on finding a true “Earth analog”: a terrestrial planet in an Earth-type orbit, around an Earth-like star.

Working toward that goal, four collaborating international teams of astronomers have recently announced the discovery of a seemingly inconspicuous cold terrestrial exoplanet around a binary red dwarf star system. What makes this discovery significant, however, is that this newly found alien world is the first to have an orbit of approximately 1 Astronomical Unit, or AU, from its host star, which is the same distance between the Earth and Sun, indicating that such Earth-type orbits might indeed be common in other exoplanetary systems as well.

Even though red dwarf stars are the most abundant stellar population in the Milky Way galaxy, possibly comprising up to 80 percent of the galaxy’s total number of stars, they had systematically been ignored for years by astronomers in their search for exoplanets. With masses and sizes ranging from approximately 1/10th to 1/3rd that of the Sun and a metallicity (abundance in chemical elements heavier than helium) substantially lower than that of Sun-like stars, red dwarfs were seen as very poor candidates for forming and maintaining any exoplanetary systems. In addition, the lower luminosity of red dwarf stars made them very difficult targets for study.

Yet the advent of observational exoplanetary research during the last two decades with a new generation of advanced ground- and space-based instruments of high-sensitivity has revealed a multitude of planets and planetary systems around red dwarf stars, leading scientists to calculate that there might be billions of exoplanets in the Milky Way, many of which potentially habitable, orbiting these previously neglected, inconspicuous stars.

Full article here:

http://www.americaspace.com/?p=63806

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