≡ Menu

Ross 128 b: A ‘Temperate’ Planet?

At 10.89 light years from Earth, Ross 128 is the twelfth closest star to the Solar System, a red dwarf (M4V) first cataloged in 1926 by astronomer Frank Elmore Ross. Now we have news that a team working with the European Southern Observatory’s HARPS spectrograph (High Accuracy Radial velocity Planet Searcher) at the La Silla Observatory in Chile has discovered an Earth-sized planet orbiting Ross 128 every 9.9 days, a world whose orbit could conceivably place it in the habitable zone, where liquid water could exist on the surface. That gives us a second nearby world in an interesting orbit, the other of course being Proxima Centauri b.

What gives the Ross 128 b detection a wrinkle of astrobiological interest is that the star the planet orbits is relatively inactive. Red dwarfs are known for the flares that can flood nearby planets with ultraviolet and X-ray radiation. Compounded with the fact that habitable zone planets must orbit quite close to a parent M-dwarf (given the star’s small size and low temperature compared to the Sun), such flares could act as a brake on the development of life.

Ross 128 b may thus have a higher likelihood for astrobiological activity than Proxima b, assuming that it actually is in the habitable zone. Right now the team behind this work, led by Xavier Bonfils (Université Grenoble Alpes) hedges its bets by referring to the planet as ‘temperate’ and ‘close to the inner edge of the conventional habitable zone.’

Image: This artist’s impression shows the temperate planet Ross 128 b, with its red dwarf parent star in the background. This planet, which lies only 11 light-years from Earth, was found by a team using ESO’s unique planet-hunting HARPS instrument. The new world is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. Ross 128 b will be a prime target for ESO’s Extremely Large Telescope, which will be able to search for biomarkers in the planet’s atmosphere. Credit: ESO/M. Kornmesser.

Let’s dig into ‘habitability’ a bit more. Ross 128 is a star with about half the surface temperature of the Sun. The newly discovered planet orbits it some twenty times closer than the Earth to the Sun, while receiving 1.38 times the irradiation the Earth receives. The researchers derive an equilibrium temperature between -60 and 20°C, equilibrium temperature being determined without regard to any atmosphere. An atmosphere would substantially affect surface temperature, as the example of Venus reminds us all too well in our own system. With an equilibrium temperature of 227 K, Venus’ actual surface temperature is around 740 K.

Thus trying to figure out Ross 128 b’s placement in or near the habitable zone is a tricky proposition. Consider this from the paper:

For assumed albedos of 0.100, 0.367, or 0.750, its equilibrium temperature would thus be 294, 269, or 213 K. Using theoretically motivated albedos, the Kopparapu et al. (2017) criteria place the planet firmly outside the habitable zone, while Kopparapu et al. (2013), Yang et al. (2014), and Kopparapu et al. (2016) find it outside, inside and just at the inner edge of the habitable zone.

The key point here is that the habitable zone will take a good deal of future work to pin down. The paper resumes with this statement explaining the choice of the word ‘temperate’:

The precise location of the inner edge is therefore still uncertain, as it depends on subtle cloud-albedo feedbacks and on fine details in complex GCM [global climate] models. The habitable zone most likely will not be firmly constrained until liquid water is detected (or inferred) at the surface of many planets. Meanwhile, it is probably preferable to refer to Ross 128 b as a temperate planet rather than as a habitable zone planet.

Image: This image shows the sky around the red dwarf star Ross 128 in the constellation of Virgo (The Virgin). It was created from images forming part of the Digitized Sky Survey 2. Ross 128 appears at the centre of the picture. Close inspection reveals that Ross 128 has a strange multiple appearance as this image was created from photographs taken over a more than forty year period, and the star, which is only 11 light-years from Earth, moved across the sky significantly during this time. Ross 128 is a “quiet” red dwarf star and is orbited by Ross 128 b, an exoplanet with a similar mass and temperature to the Earth. Credit: Digitized Sky Survey 2. Acknowledgement: Davide De Martin.

Whether or not Ross 128 b is in the classic habitable zone, it presents an appealing target for future observation with instruments like the European Extremely Large Telescope. Low stellar activity bodes well for the survival of planetary atmospheres and the potential emergence of life on planets orbiting M-dwarfs. Thus this interesting planet will appear high on our target lists for future atmospheric characterization and the search for potential biomarkers.

“New facilities at ESO will first play a critical role in building the census of Earth-mass planets amenable to characterisation. In particular, NIRPS, the infrared arm of HARPS, will boost our efficiency in observing red dwarfs, which emit most of their radiation in the infrared. And then, the ELT will provide the opportunity to observe and characterise a large fraction of these planets,” concludes Bonfils.

The paper is Bonfils et al., “A temperate exo-Earth around a quiet M dwarf at 3.4 parsecs,” accepted at Astronomy & Astrophysics. I’ll post a link to the online abstract and preprint as soon as they become available.

tzf_img_post

Comments on this entry are closed.

  • Mauldred November 15, 2017, 9:40

    A very good news indeed, and another possible target for Breakthrough Starshot. It looks like most nearby red dwarves harbour an Earth-sized planet within or close to their habitable zone (Ross 128, Proxima Cen, Kapteyn’s Star, GJ 667C, Trappist-1, LHS 1140 etc). And as it’s easier to detect a planet around such small stars if they aren’t too far away, we can reasonably use the mediocrity principle to say that it is the case for most red dwarves situated in the habitable region of our galaxy.

    The current estimates give a probability of 40% for a red dwarf star to have at least 1 Earth-sized world orbiting it. If half of these worlds are within the habitable zone of their parent star, and even if only 1% of these have a nitrogen atmosphere and water flowing on their surface, that makes a whopping number of habitable planets waiting out there to be colonised… or already inhabited by an alien civilisation, which would reinforce the Fermi paradox.

  • ljk November 15, 2017, 9:41

    Let us not forget that Ross 128 was the subject of a possible SETI detection signal just this past summer:

    https://www.centauri-dreams.org/?p=38137

    It was blamed on a geostationary satellite, but as happened with the SETI detection of HD 164595 by Russia in 2016, no actual satellites were named or even their signal frequencies revealed. It was more like an educated guess, which the media and professional communities ate up with no further argument for their various reasons (relief, embarrassment, etc.).

    https://www.centauri-dreams.org/?p=36248

    Now that we know of an Earth-sized exoplanet circling Ross 128 which may also be in its habitable zone, perhaps we should give that system’s SETI detection a more serious and in-depth look.

    We still know so little about so much when it comes to the Universe, including our cosmic neighbors.

  • ljk November 15, 2017, 10:12

    The Planetary Society’s take on the Ross 128 exoworld:

    http://www.planetary.org/blogs/jason-davis/2017/20171115-ross-128b.html

    To quote:

    As if this news wasn’t interesting enough, there’s also a SETI (search for extraterrestrial intelligence) angle to the story. Earlier this year, Ross 128 made headlines because it appeared to be sending out a semi-repeating radio signal. The signal was later explained to likely be a geostationary satellite in Earth orbit, but today’s announcement puts Ross 128 back in play as a star system potentially capable of hosting life. The newly found exoplanet will soon be the target of many future astronomical observations—including SETI searches.

    “We are considering additional follow-up in light of the new discovery at radio and optical wavelengths,” said Andrew Siemion, the director of the SETI Research Center at the University of California, Berkeley. “Nearby exoplanets are particularly exciting from a SETI perspective, as they permit us to search for and potentially detect much weaker signals than from more distant targets.”

    Red dwarfs are also a frequent target for SETI searches, mostly because of their prevalence. The Breakthrough Listen group, as well as the SETI Institute, are currently listening for radio signals coming from stars close to Earth.

    In May, Abel Méndez, an associate professor of physics and astrobiology at the University of Puerto Rico, led a campaign at Arecibo Observatory to examine radio emissions coming from several nearby red dwarf stars.

    Méndez’s team wasn’t looking for extraterrestrial signals; they were hoping to learn how red dwarf flares interacted with exoplanets. The observing target list included a couple stars that had exoplanets, as well as a few that didn’t—including, at the time, Ross 128.

    When Méndez’s team looked at the results, they saw something peculiar: some strange, semi-repeating signals coming from Ross 128. The signals had a frequency around 5 gigahertz, right in the middle of the 1-to-15-gigahertz range targeted by typical SETI searches. The signals didn’t appear to be local interference, since observations made of other stars by Arecibo around the same time didn’t see the signal. So in July, Arecibo, the SETI Institute’s Allen Telescope Array, and the Green Bank Telescope listened again.

    None of the telescopes heard anything. A subsequent analysis by Breakthrough Listen, accepted for publication in the International Journal of Astrobiology, concluded the signal Méndez’s team saw probably came from one of several geostationary satellites in the direction of Ross 128.

    [And I ask yet again: WHICH geostationary satellites were they? Do they know for a fact that is where the signals came from and not Ross 128? Or is this just an educated, Occam’s razor style guess? Perhaps now the newly found alien planet there will get the SETI community to be more proactive this time – though it is rather parochial of us to assume that alien intelligences are only assigned to terrestrial type worlds. But, hey, baby steps, even 57 years after Project Ozma, right?]

    • andy November 15, 2017, 16:28

      According to this page, there were quite a number of known satellites in the vicinity of Ross 128 on the sky at the time. Humans do have quite a talent for spreading our rubbish throughout the environment, this goes for space as well.

      I suppose it’s more exciting to imagine that there’s a conspiracy to cover it up though. The truth is out there, Agent Mulder!

      • Raimo Kangasniemi November 15, 2017, 20:43

        I don’t think a conspiracy was meant – just that the most likely solution (geostationary satellite) was chosen and accepted without there being firm evidence that it was the cause.

        • ljk November 16, 2017, 10:16

          Correct – I certainly was NOT implying a conspiracy here. What I am asking for is detailed evidence for their claim that it is a terrestrial satellite. As I said about the Russian SETI event of 2016, they also claimed it was an old Soviet spy satellite yet failed to say which one and seemed very eager to dismiss the whole thing. The media dutifully parroted what they heard as usual and also considered it case closed. This is not science.

          It is a shame that the whole concept of alien life is constantly tainted and derailed by both the UFO fringe cult types and those who claim scientific objectivity yet seem eager to bury the issue for reasons that have little to do with actual science, except to use it as a front to maintain cultural and professional credibility.

          SETI really needs to get its act together across the board. Breakthrough Initiatives is a step in the right direction, at least, after decades of the field wandering in the scientific and cultural wilderness, with just a relatively few serious practitioners trying to keep it aloft in a sea of ignorance and professional disdain. Knowing whether we are alone or not in the Universe is one of the most important questions we will ever ask: We need an answer and it needs to be done right.

  • ljk November 15, 2017, 10:41

    eso1736 — Science Release

    Closest Temperate World Orbiting Quiet Star Discovered

    ESO’s HARPS instrument finds Earth-mass exoplanet around Ross 128

    15 November 2017

    A temperate Earth-sized planet has been discovered only 11 light-years from the Solar System by a team using ESO’s unique planet-hunting HARPS instrument.

    The new world has the designation Ross 128 b and is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life.

    Ross 128 b will be a prime target for ESO’s Extremely Large Telescope, which will be able to search for biomarkers in the planet’s atmosphere.

    The release, images and videos are available on:

    http://www.eso.org/public/news/eso1736/

  • Harry R Ray November 15, 2017, 11:02

    Paul Gilster: HERE’S THE LINK! Either http://www.eso.org/public/archives/re…eso1736/eso1736a.pdf or just http://www.eso.org/public/archives/re…eso1736/eso1736a.pdf From the PDF I obtained MORE SPECIFIC DATA: Msini=1.40Mearth +/- 0.21Mearth, Temperature RANGE=213 to 301 Kelvins(the orbital period remains the same at 9.9 days).

  • Harry R Ray November 15, 2017, 11:05
  • Harry R Ray November 15, 2017, 11:11

    I keep typing in the link WITHOUT the “http://” but it is POSTED WITH the “http:// BEFORE the “www” YOU CANNOT ACCESS THE PDF if you INCLUDE the “http://” in the link, so to access it, i guess you have to “google” the link with the “http://” part DELETED! That’s how I accessed it.

  • Harry R Ray November 15, 2017, 11:19

    79 thousand years from now,Ross 128 will overtake Proxima Centauri b and become the closest star to the SUN.

  • Doug DV November 15, 2017, 11:27
  • Harry R Ray November 15, 2017, 12:11

    Abel Mendez has FINALLY REVISED the “data” section of HEC(first time since May 11) and puts the BEST FIT to the Ross 128b temperature RANGE at 280K(I have absolutely NO idea what criteria he used). He still has NO POWER and has to run HEC on a generater, which is probably why he did NOT include the LATEST Kepler habitable planet candidates(http://www.drew ex machina.com) in the data set YET(I hope he can do this VERY SOON).

    • Andrew LePage November 16, 2017, 10:45

      Harry, thanks for the plug (the link to my Kepler-related articles can be found here: http://www.drewexmachina.com/tag/kepler-mission/ ). As for the temperature range cited in the Ross 128b discovery paper (as well as for many other exoplanet finds), the temperature ranges they cite are essentially useless in ascertaining the actual surface temperature of this world. It is the temperature based on the assumption of an airless blackbody with a range of assumed albedo values. Since any potentially habitable world (in the Earth-like sense) would have an atmosphere, there would be a greenhouse effect which needs to be taken into account (and if aerosols are present, even an anti-greenhouse effect). A much more informative figure to help assess the conditions on a planet is the mean stellar flux (i.e. the amount of energy a planet receives from its sun compared to the Earth).

      • Andrei November 18, 2017, 14:09

        Yes it is either effective or blackbody temperature, Earth have 255 and 279K for those. So it is not useless, we learn the planet is indeed in habitable zone. Earth would be kept warm there, but little light so plant life would not do well on such a planet and most energy in low frequency red and infrared. So even with a perfect atmosphere, liquid water and all other conditions – it is a question if planets like this is really suitable for life as we know it.

    • ljk November 16, 2017, 11:56

      An update on the Arecibo radio observatory from The Atlantic:

      https://www.theatlantic.com/science/archive/2017/11/arecibo-observatory-hurricane-maria/545522/

  • Steve Muise November 15, 2017, 12:21

    Not to be a party pooper, but the duration of our observations of Ross 128 comprise only a tiny fraction of the star’s lifespan. For all we know Ross 128 could have been active right up until 500 years ago and we would not necessarily know it.

    • Andrew LePage November 16, 2017, 10:38

      I don’t know exactly what you mean by “active” but considering that Ross 128 has an age in the range of 5+ to maybe 10 billion years out of a total expected main sequence lifetime of on the order of a trillion years, there is no reason to believe that Ross 128 has magically become “inactive” just as we are observing it so early in its evolution. Besides, if something strange happened with Ross 128, we would know about it in only 11 years (not 500) because it is only 11 light years away.

      • hiro November 16, 2017, 19:05

        He meant in the past (like around 1500s), we didn’t have cool toys back then to detect anything. People still “debated” whether the Earth was the center of the universe.

        • ljk November 17, 2017, 10:14

          Actually that is a bit of a misnomer: Back in the day many folks thought Earth and humanity were not at the center of the Universe – implying that we were the focus of existence – but at the bottom of a cosmic pit, with only hell being lower. That is why Galileo et al were so excited to learn that the stars were other suns and possibly had planets, which meant Earth and by extension our species were also elevated among the heavens.

          See this work by Dennis Danielson, The Book of the Cosmos, for the details:

          https://fab.lexile.com/book/details/9780738202471/

          http://english.ubc.ca/persons/dennis-danielson/

    • ljk November 16, 2017, 11:06

      What would make Ross 128 or any other red dwarf stop flaring, assuming that not all such suns behave the same way?

      • Michael November 17, 2017, 8:33

        A slow rotation rate caused by excess momentum been held by planets in orbit around the red dwarf. Ross may have many more planets yet to be discovered.

        • ljk November 17, 2017, 10:17

          So you are saying that if there are enough planets orbiting a red dwarf star, they can by extension control its flaring? So the quieter a red dwarf the more planets it has?

          • Adam Crowl November 17, 2017, 19:56

            Not exactly. More planets are a sign the excess angular momentum has been bled off. Magnetic activity is driven by angular momentum of the star, which is shed via magnetic-coupling with the out-going stellar wind.

      • Michael Poole November 30, 2017, 20:08

        Time. Flaring is just a billion year long epoch in a trillion year life of a red dwarf.

  • jonW November 15, 2017, 12:28

    Hello Paul–back in July you wrote about this star (in the context of an unexplained radio source): “More significantly, it is an active flare star, capable of unpredictable changes in luminosity over short periods.” I’m curious, where does the change originate in describing its status as becalmed now?

    • Paul Gilster November 15, 2017, 16:17

      jonW, I don’t recall my source in July, but everything I’m seeing now points to a quieter star. Quieter, that is, in relation to other M-dwarfs like Proxima. I’ll dig around to see if there is any active disagreement about its flare status. I may have simply mis-read something in the earlier post.

      • ljk November 16, 2017, 10:42

        Here is the link to the Centauri Dreams article on Ross 128 from July 19, which I had also posted near the top of this comments thread:

        https://www.centauri-dreams.org/?p=38137

        From my reading of that article, it sounds like the Arecibo astronomers who made the study were theorizing that the strange radio signals from Ross 128 were possibly due to Type 2 solar flares. To repeat, this was their theory, not a determined fact.

        So Ross 128 may indeed be a “quiet” red dwarf and the speculation made by an astronomers that flares caused the radio signals has been misinterpreted as the actual answer. So what we need is the actual scientific data showing whether the star flares up or not.

      • Ashley Baldwin November 17, 2017, 13:46

        I think “quiet” is a relative term. It’s flare frequency is now low but it still retains a serious overall erg output through those it does emit. It is as Ramirez Ramsses always says , the hab zone concept applies best to larger early K to late F dwarf stars and doesn’t necessarily hold as well for M dwarfs and especially not later types.

        That said I can’t help feeling that we are circling in holding mode at present . Good at discovering exoplanets but not so good at characterising them above and beyond basic mass, radius , density and orbital features. The sooner we have JWST and METIS on the E-ELT operational ( which is optimised for both direct imaging and high dispersion spectroscopy of nearby M dwarf planets like Ross 128b and Proxima b) , the better and we can move to the next level. Thanks to Hubble and Spitzer many of the techniques have already been refined. I know Ignas Snellen for one can’t wait to get his teeth into Ross 128b ! Simulations are fine as far as they go but are only as good as the input data.

        – As Sherlock Holmes said, ” Data is everything . Without it facts are made to fit theories rather than theories to fit facts “.

  • Joe H November 15, 2017, 13:15

    Based in the illustration, the star looks pinkish white. So assuming Ross 128-b is an Earth clone, would its sun look red to any inhabitants looking at it through a nitrogen oxygen atmosphere?

    • FrankH November 16, 2017, 15:36

      Ross 128’s temperature of around 3200K is equivalent to an incandescent or halogen bulb (“warm white”). M dwarfs have prominent and numerous absorption lines in their spectra, so their colors may not be an exact match to a black body at their temperature, but in most cases, it should be close enough.

      Here’s a color-temperature comparison for lights, but should be close enough to star colors:

      https://siliconlightworks.com/image/data/Graphics/Silicon-Lightworks-Color-Temperature-Comparison.jpg

    • Ashley Baldwin November 18, 2017, 7:25

      It would look orange. “Red dwarf” was coined for those stars ( including late K spectrum too ) that emitted a larger proportion of their radiation at the redder ( including ‘ invisible’ IR) end of the spectrum rather than exclusively so.

  • Brett November 15, 2017, 13:31

    The star is at least 9 billion years old. Even if this earth-like planet was habitable around it earlier in the star’s life, the planet is probably geologically inert and has been for a long time. That would be problem for any planet, but especially for one around a red dwarf star that needs a magnetic field to keep the star’s flaring from stripping off its atmosphere.

    • ljk November 16, 2017, 10:43

      What would make Ross 128b geologically inert exactly?

      • Michael November 17, 2017, 8:35

        The carbonate and tectonic cycle may have ground to a halt as the planet lost its internal heat.

        • Ashley Baldwin November 17, 2017, 13:53

          Difficult to pin down its age exactly. Estimates as low as 6 Gig years exist which could allow a big terrestrial planet to still retain enough internal heat to be active. Though tectonics likely also depends on water for lubrication – water that may have been stripped away consistently through the parent star’s extended active phase . In terms of greater stellar age given the proximity of Ross 128b to its primary it is highly likely to have been subject to substantial tidal heating which could extend its internal heat indefinitely though at risk of making it an uninhabitable Super Venus. Anything and everything applies.

    • Michael Fidler November 19, 2017, 10:23

      I believe that these planets in a much smaller solar system would have more large impacts that would keep plate tectonics active and bring huge amounts of water.

      Large meteorite impacts drove plate-tectonic processes on the early Earth.
      https://phys.org/news/2017-09-large-meteorite-impacts-drove-plate-tectonic.html
      https://cosmos-magazine.imgix.net/file/spina/photo/12010/170925-TectonicDiagram-Full.jpg?fit=clip&w=2560

      In doing so the subducting slabs would take water to the outer core that would be split and release huge amounts of oxygen in massive volcanic eruptions.

      WHEN WATER MET IRON DEEP INSIDE THE EARTH, IT MIGHT HAVE CREATED CONDITIONS FOR LIFE.
      “Reservoirs of oxygen-rich iron between the Earth’s core and mantle could have played a major role in Earth’s history, including the breakup of supercontinents, drastic changes in Earth’s atmospheric makeup, and the creation of life, according to recent work from an international research team published in National Science Review.
      The team—which includes scientists from Carnegie, Stanford University, the Center for High Pressure Science and Technology Advanced Research in China, and the University of Chicago—probed the chemistry of iron and water under the extreme temperatures and pressures of the Earth’s core-mantle boundary.
      When the action of plate tectonics draws water-containing minerals down deep enough to meet the Earth’s iron core, the extreme conditions cause the iron to grab oxygen atoms from the water molecules and set the hydrogen atoms free. The hydrogen escapes to the surface, but the oxygen gets trapped into crystalline iron dioxide, which can only exist under such intense pressures and temperatures.
      Using theoretical calculations as well as laboratory experiments to recreate the environment of the core-mantle boundary, the team determined that iron dioxide can be created using a laser-heated diamond anvil cell to put materials under between about 950 and 1 million times normal atmospheric pressure and more than 3,500 degrees Fahrenheit.
      “Based on our knowledge of the chemical makeup of the slabs that are drawn into the Earth’s deep interior by plate tectonics, we think 300 million tons of water could be carried down to meet iron in the core and generate massive iron dioxide rocks each year,” said lead author Ho-kwang “Dave” Mao.
      These extremely oxygen-rich solid rocks may accumulate steadily year-by-year above the core, growing into gigantic, continent-like sizes. A geological event that heated up these iron dioxide rocks could cause a massive eruption, suddenly releasing a great deal of oxygen to the surface.
      The authors hypothesize that such an oxygen explosion could put a tremendous amount of the gas into the Earth’s atmosphere—enough to cause the so-called Great Oxygenation Event, which occurred about 2.5 billion years ago and created our oxygen-rich atmosphere, conditions that kickstarted the rise oxygen-dependent life as we know it.
      “This newly discovered high-temperature and intense-pressure water-splitting reaction affects geochemistry from the deep interior to the atmosphere” said Mao. “Many previous theories need to be re-examined now.”

      https://carnegiescience.edu/news/when-water-met-iron-deep-inside-earth-it-might-have-created-conditions-life
      https://carnegiescience.edu/sites/carnegiescience.edu/files/resize/imagepicker/74/PRMaoWhenIronMetWater-800×371.jpg

      • Michael Fidler November 29, 2017, 1:55

        Initiation of Plate Tectonics on Exoplanets with Significant Tidal Stress.

        “Plate tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth’s climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not plate tectonics may occur on a terrestrial planet is if the stress on a planet’s lithosphere from mantle convection may overcome
        the lithosphere’s yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of plate tectonics on exoplanets have neglected tidal stresses in the planet’s lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for plate tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience plate tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active plate tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity”.

        https://arxiv.org/pdf/1711.09898.pdf

  • Adam November 15, 2017, 15:52

    Nice points Larry. I wonder – once Puerto Rico is running normally again – if Dr Mendez will re-examine their data.

  • Anthony November 15, 2017, 16:08

    Now that we know the orbital period (9.9 earth days) can someone look back at SETI’s follow up radio observations and see if this planet was, or was not, behind its own star at the time? Also, could the sharply curving orbit explain the striations observed in the first possible radio detection?

    • andy November 15, 2017, 17:22

      The TGAS parallax for Ross 154 is 295.80±0.54 milliarcseconds, which translates into a distance of 11.026±0.020 light years. Expressing the error value in light days so it is easier to compare to the orbital period, that gives an uncertainty of 7.3 light days. So the time uncertainty due to the error on the distance to the star is comparable to the orbital period of the planet, and it wouldn’t be possible to say for certain where the planet was in its orbit at the time any possible signal may have left the system.

      Since transits do not occur, it is unlikely that eclipses occur and so even if the planet were on the far side of the star, it would not be hidden from view.

  • Michael Fidler November 15, 2017, 23:05

    I have been doing a little research and have come up with some interesting clues. The picture of the geostationary satellite positions is a little deceiving since over the 10 minute time of the weird signal Ross 128 would have moved two and a half degrees in relation to the satellites.
    http://phl.upr.edu/press-releases/theweirdsignal
    http://www.hpcf.upr.edu/~abel/phl/AOSearch/satellite.png
    http://seti.berkeley.edu/ross128.pdf

    As you can see in this image that as the earth rotates the stars move thru the field of the geostationary satellites.
    https://www.noao.edu/outreach/press/pr01/images/sat_sky_wide_med.jpg
    What is interesting is that Ross 128 would be crossing thru the field of all the geostationary satellites in a 24 hour period, but only a few would come close to its position of just o.48′ north of the equator. An example would be satellite 19548 which after some 16 minutes would have crossed very close to Ross 128 position. Now this satellite is the old TDRS 3 that was launched on Sept. 29, 1988 and is still partially operational. (see this website) https://www.n2yo.com/satellites/?c=10

    Here is the pièce de résistance: since we are sending a relatively small beam up to these satellites, any of the ones that pass near Ross 128 would leak the signals in its direction. Basically would are sending several very strong tight beams of information at Ross 128 every 24 hours depending on how many geostationary satellites come close enough to it. If an exo civilization or a repeating beacon was at Ross 128 and was re-transmitting the signal back toward us then we would be receiving it some 22 years after it was transmitted from earth. There are now almost 500 geostationary satellites in orbit but in 1995 only about 200 were active including the TDRS 3 satellite . https://www.n2yo.com/satellites/?c=10
    What we should be looking at is what GeoSats crossed near Ross 128 path in that time period and at what freqs were the signals being sent to them from their earth stations. If this resulted in a match then maybe the Weird! signal could be deciphered.

  • Michael Fidler November 15, 2017, 23:11

    Would you be so kind as to correct this:
    Basically we are sending several very strong tight beams of information at Ross 128 every 24 hours depending on how many geostationary satellites come close enough to it.
    Thank you
    Michael

    • ljk November 16, 2017, 10:58

      Very nice work, Michael. Can you tell us just how strong those terrestrial beams are and if they could reach Ross 128 in a form that could be determined as artificial? I wonder what other star systems are also being “pinged” in this manner and how often as humanity goes about its daily geosat business?

      • Michael Fidler November 16, 2017, 23:27

        Thanks ljk, as to answer your questions, according to what are uplink earth stations power levels: 1000 watts. The variety of signals can be from open air digital tv (Mostly Religious) to your call to Aunt Wilma, but most of it is scrambled and for banks and military, encrypted.
        The bad news is that both the Ross 128 and the HD 164595 the Freqs 4.6 to 4.8 Ghz and 11 Ghz that the signals were on are in the range of the downlink freqs for GeoSats.
        The good news is that because the uplink earth stations are north or south of the equator they will cover a larger area of the sky to the amount of some 10 degrees north or south of the Celestial equator.
        This is because of the parallax of the stations, an uplink from Alaska would shoot a beam that would end up pointing at stars 9 to 10 degrees south of the Celestial equator. That will include the following stars within 16 light years: Barnard’s Star, Wolf 359, Epsilon Eridani, Ross 128, Procyon, Luyten’s Star, Ross 614, Wolf 424, GJ 1002. The GeoSats are separated by 2 degrees from each other so the beams are probably 1 degree in diameter. https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs

        There is plenty of material on the internet about the GeoSats and what is being transmitted and at what freqs, so anyone that has a good knowledge of the subject might be able to delve into this a little better. Just wonder what the Aliens may be thinking of us!

        • Michael Fidler November 17, 2017, 2:07

          C Band Frequency Usage
          Detailed view of the C band frequency usage in the US.

          Chart of United States frequency allocations between 3.7 to 8.025GHz.

          https://sites.google.com/site/interfacebus/Home/radar-gear/c-band-frequency-usage

          Good chart covering the 4.6 to 4.8 Ghz freq, but from 1996, does anyone have a chart for the current allocation?

          • ljk November 17, 2017, 14:17

            Of course if there are other technological civilizations in the galaxy and, assuming at least some of them operate their technologies in manners similar to ours and have similar attitudes regarding alien life, they could be inadvertently spreading their electromagnetic noise into deep space as well.

  • ijv November 16, 2017, 1:40

    According to the star chart in that Planetary Soc. article. Ross 128 is almost bang on the ecliptic. Is there any chance of it being occulted by a solar system object and would that reveal any useful information?

  • Andrew LePage November 16, 2017, 10:26

    For readers interested in another assessment of the potential habitability of Ross 128b, here is my latest “Habitable Planet Reality Check”:

    http://www.drewexmachina.com/2017/11/16/habitable-planet-reality-check-the-nearby-ross-128/

  • ljk November 16, 2017, 11:32
  • DJ Kaplan November 16, 2017, 13:21
  • Spaceman November 16, 2017, 14:26

    Paul, is it true that the next generation of ground-based telescopes might be able to take spectroscopic measurements of this newfound terrestrial world’s atmosphere (assuming it has one)? I wonder if abiogenesis occurred on Ross 128b, or, even if it did occur, the hypothetical nascent life got snuffed out by a ‘Gaian Bottleneck.’

    • Ashley Baldwin November 17, 2017, 14:01

      Ross 128 b and Proxima b ( with any other nearby M dwarf planets ) are already prime targets for the METIS Imager ( 2.9- 10 microns )on the E-ELT as well as high dispersion spectroscopy . Hopefully from 2025. G-Clef on the GMT too though this does not have either an integral field unit or imager as a first generation instrument so will be much less effective . Numerous papers published on this area on arXiv over the last three years . Ignas Snellen at Leiden University who is heavily involved with METIS ( as well as HIRES) tells me he can’t wait .

  • Michael November 17, 2017, 8:38

    I wonder if these tidally locked planets may have an other strike against them in that they may form large star facing hurricanes, so called eyeball worlds. If these hurricanes are there they could force water in the air above the cold trap allowing UV to do more damage even if a ozone layer has formed.

    • Michael Fidler November 17, 2017, 10:08

      Modelling climate diversity, tidal dynamics and the fate of volatiles
      on TRAPPIST-1 planets.

      “TRAPPIST-1 planets are invaluable for the study of comparative planetary science outside our Solar System and possibly habitability.
      Both Time Transit Variations (TTV) of the planets and the compact, resonant architecture of the system suggest that TRAPPIST-1
      planets could be endowed with various volatiles today. First, we derive from N-body simulations possible planetary evolution
      scenarios, and show that all the planets are likely in synchronous rotation. We then use a versatile 3-D Global Climate Model (GCM)
      to explore the possible climates of cool planets around cool stars, with a focus on the TRAPPIST-1 system. We look at the conditions
      required for cool planets to prevent possible volatile species to be lost permanently by surface condensation, irreversible burying or
      photochemical destruction. We also explore the resilience of the same volatiles (when in condensed phase) to a runaway greenhouse
      process. We find that background atmospheres made of N2, CO or O2 are rather resistant to atmospheric collapse. However, even
      if TRAPPIST-1 planets were able to sustain a thick background atmosphere by surviving early X/UV radiation and stellar wind
      atmospheric erosion, it is difficult for them to accumulate significant greenhouse gases like CO2, CH4 or NH3. CO2 can easily condense
      on the permanent nightside, forming CO2 ice glaciers that would flow toward the substellar region. A complete CO2 ice surface cover
      is theoretically possible on TRAPPIST-1g and h only, but CO2 ices should be gravitationally unstable and get buried beneath the water
      ice shell in geologically short timescales. Given TRAPPIST-1 planets large EUV irradiation (at least ∼ 103 × Titan’s flux), CH4 and
      NH3 are photodissociated rapidly and are thus hard to accumulate in the atmosphere. Photochemical hazes could then sedimentate
      and form a surface layer of tholins that would progressively thicken over the age of the TRAPPIST-1 system. Regarding habitability,
      we confirm that few bars of CO2 would suffice to warm the surface of TRAPPIST-1f and g above the melting point of water. We also
      show that TRAPPIST-1e is a remarkable candidate for surface habitability. If the planet is today synchronous and abundant in water,
      then it should always sustain surface liquid water at least in the substellar region, whatever the atmosphere considered.”

      https://arxiv.org/pdf/1707.06927.pdf

      They must of read your mind!

    • ljk November 17, 2017, 10:32

      Your comment reminds me of the National Geographic program from 2005 titled Extraterrestrial. The first exoworld they depict, named Aurelia, circles a red dwarf and is tidally locked, where one side is dominated by a massive hurricane far bigger than anything on Earth. They also show how the creatures on that planet deal with solar flares.

      https://en.wikipedia.org/wiki/Extraterrestrial_(TV_documentary)

      https://www.space.com/1137-tv-review-national-geographic-extraterrestrial.html

  • Michael Fidler November 17, 2017, 9:42

    PLANET-PLANET OCCULTATIONS IN TRAPPIST-1 AND OTHER EXOPLANET SYSTEMS.

    “We explore the occurrence and detectability of planet-planet occultations (PPOs) in exoplanet systems. These are events during which a planet occults the disk of another planet in the same
    system, imparting a small photometric signal as its thermal or reflected light is blocked. We focus on the planets in TRAPPIST-1, whose orbital planes we show are aligned to < 0.3 ◦ at 90% confidence.
    We present a photodynamical model for predicting and computing PPOs in TRAPPIST-1 and other systems for various assumptions of the planets’ atmospheric states. When marginalizing over the
    uncertainties on all orbital parameters, we find that the rate of PPOs in TRAPPIST-1 is about 1.4 per day. We investigate the prospects for detection of these events with the James Webb Space Telescope, finding that ∼10 − 20 occultations per year of b and c should be above the noise level at 12 − 15 µm. Joint modeling of several of these PPOs could lead to a robust detection. Alternatively, observations with the proposed Origins Space Telescope should be able to detect individual PPOs at
    high signal-to-noise. We show how PPOs can be used to break transit timing variation degeneracies, imposing strong constraints on the eccentricities and masses of the planets, as well as to constrain
    the longitudes of nodes and thus the complete three-dimensional structure of the system. We further show how modeling of these events can be used to reveal a planet’s day/night temperature contrast
    and construct crude surface maps. We make our photodynamical code available on github."

    http://astrobiology.com/2017/11/planet-planet-occultations-in-trappist-1-and-other-exoplanet-systems.html

    Very well done paper with a lot of good diagrams. This may also have the ability to detect details on the exoplanets surface. The question I’m wondering about with systems like the Trappist1 where the planets are the far side and fully illuminated could a flare on the back side of the red dwarf to the earth act like a cameras flashbulb in the UV to give a much better contrast ratio.

    • Michael Fidler November 18, 2017, 6:35

      “The Flaring Activity of M Dwarfs in the Kepler Field.
      2017 November 1
      “Flare events are mainly due to magnetic reconnection and thus are indicative of stellar activity. The Kepler Space with unprecedented high photometric precision in flux measurements. It is perfectly suitable for carrying out a statistical study of flares. Here we present 540 M
      dwarfs with flare events discovered using Kepler long-cadence data. The normalized flare energy, as defined by the ratio to bolometric stellar luminosity, Lflare bol L , is used to indicate the flare activity. We find that, similar to the X-ray luminosity relation, the Lflare bol L versus Prot relation can also be described with three phases,
      supersaturation, saturation, and exponential decay, corresponding to an ultra-short period, a short period, and a long period. The flare activity and the number fraction of flaring stars in M dwarfs rise steeply near M4, which is consistent with the prediction of a turbulent dynamo. The size of starspots are positively correlated with flare activity. The Lflare bol L ratio has a power-law dependence on LH bol a L , a parameter indicative of stellar chromosphere activity. According to this relation, a small enhancement in chromosphere activity may cause a huge rise in flare energy, which suggests that superflares or hyperflares may not need an extra excitation mechanism. Through a comparison study, we suggest that flare activity is a more suitable indicator for stellar activity, especially in the boundary region.”

      “However, contrary to what is expected, some M dwarfs with strong flares do not show any light variation caused by starspots. Follow-up observations are needed to investigate this problem.”

      http://iopscience.iop.org/article/10.3847/1538-4357/aa8ea2/pdf

      The FUV Flares of Active and Inactive M Dwarfs.
      Know Thy Star
      2017 October 11

      Very good Powerpoint presentation.

      http://nexsci.caltech.edu/conferences/2017/knowthystar/loyd_a.pdf

  • Michael Fidler November 17, 2017, 9:51

    Interstellar communication. III. Optimal frequency to maximize data rate.

    “We recommend expanding SETI efforts towards targeted (at us) monochromatic (or narrow band) X-ray emission at 0.5-2 keV energies.”

    https://arxiv.org/abs/1711.05761

    • Michael Fidler November 17, 2017, 10:03

      Maybe those X-ray flares are not flares at all! ;-}

      • Ashley Baldwin November 17, 2017, 14:06

        I seem to remember the Starflyer Alien Prime from Peter Hamilton’s ‘Pandora’s star’ communicating in just such a way by firing a “corona rupture ” device into Far Away’s star.

  • ljk November 28, 2017, 11:36

    http://astrobiology.com/2017/11/modeling-repeated-m-dwarf-flaring-at-an-earth-like-planet-in-the-habitable-zone.html

    Modeling Repeated M-dwarf Flaring at an Earth-like Planet in the Habitable Zone

    Press Release – Source: astro-ph.EP

    Posted November 27, 2017 7:37 PM

    Understanding the impact of active M-dwarf stars on the atmospheric equilibrium and surface conditions of a habitable zone Earth-like planet is key to assessing M dwarf planet habitability.

    Previous modeling of the impact of electromagnetic (EM) radiation and protons from a single large flare on an Earth-like atmosphere indicated that significant and long-term reductions in ozone were possible, but the atmosphere recovered. These stars more realistically exhibit frequent flaring with a power-law distribution of energies.

    Here we use a coupled 1D photochemical and radiative-convective model to investigate the effects of repeated flaring on the photochemistry and surface UV of an Earth-like planet unprotected by an intrinsic magnetic field. We use time-resolved flare spectra obtained for the dM3 star AD Leo, combined with flare occurrence frequencies and total energies (typically 1030.5 to 1034 erg) from the 4-year Kepler light curve for the dM4 flare star GJ1243.

    Our model results show repeated EM-only flares have little effect on the ozone column depth, but that multiple proton events can rapidly destroy the ozone column. Combining the realistic flare and proton event frequencies with nominal CME & SEP geometries, we find the ozone column for an Earth-like planet can be depleted by 94% in 10 years, with a downward trend that makes recovery unlikely and suggests further destruction. For more extreme stellar inputs O3 depletion allows a constant 0.1-1 W m−2 of UV-C at the planet’s surface, which is likely detrimental to organic complexity.

    Our results suggest that active M dwarf hosts may comprehensively destroy ozone shields and subject the surface of magnetically-unprotected Earth-like planets to long-term radiation that can damage complex organic structures. However, this does not preclude habitability, as a safe haven for life could still exist below an ocean surface.

    Modeling Repeated M-dwarf Flaring at an Earth-like Planet in the Habitable Zone: I. Atmospheric Effects for an Unmagnetized Planet

    Matt A. Tilley, Antigona Segura, Victoria S. Meadows, Suzanne Hawley, James Davenport

    (Submitted on 22 Nov 2017)

    Comments: Submitted to Astrobiology

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

    Cite as: arXiv:1711.08484 [astro-ph.EP] (or arXiv:1711.08484v1 [astro-ph.EP] for this version)

    Submission history

    From: Matt Tilley

    [v1] Wed, 22 Nov 2017 19:27:02 GMT (460kb)

    https://arxiv.org/abs/1711.08484

    Astrobiology

  • ljk November 29, 2017, 11:54

    Traces of life on nearest exoplanets may be hidden in equatorial trap, study finds

    November 29, 2017

    Simulations show that the search for life on other planets may well be more difficult than previously assumed: On planets like Proxima b or TRAPPIST-1d, unusual flow pattern could hide atmospheric ozone from telescopic observations. Ozone, which is a variety of oxygen, is seen as one of the possible traces allowing for the detection of life on another planet from afar.

    The simulations, led by Ludmila Carone of the Max Planck Institute for Astronomy, have consequences for formulating the optimal strategy for searching for (oxygen-producing) life such as bacteria or plants on exoplanets.

    http://www.mpia.de/news/science/2017-13-exoearths