Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Featured I 7 exoplanets around TRAPPIST-1

  1. Feb 20, 2017 #1

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    NASA announcement
    Wednesday, 1 pm EST. You can use the forum for time zone conversion: This post was posted 3:55 pm EST.

    While the announcement doesn't have any details, digging a bit deeper: The livestream website calls the event "Spitzer Exoplanet Science Briefing", and of course we can see what the panel is doing:

    - Thomas Zurbuchen has a management position at NASA, too unspecific.
    - Michael Gillon is working on TRAPPIST, searching for exoplanets, especially Earth-like ones, with the transit method.
    - Sean Carey works on the Spitzer telescope, an infrared telescope. It can find transit planets and map planetary disks around other stars. Microlensing events can also be observed.
    - Nikole Lewis is an expert in exoplanet atmospheres, especially with measurements in transits.
    - Sara Seager is another expert in exoplanet atmospheres, measured with transits.

    Based on that panel, I'm quite sure the announcement will be related to the atmospheric composition of some exoplanet, measured in a transit.

    Speculation: We had water (multiple times), carbon monoxide, carbon dioxide and methane already. We had hydrogen and helium. We also had sodium and titanium dioxide on very hot planets. A new observation of those gases around more exoplanets wouldn't need a press conference. Clouds were also discovered before. What is missing?
    - Nitrogen is not in the list, but nitrogen is hard to observe.
    - Oxygen would be a big sensation, as processes without life that produce oxygen are rare. While it is hard to observe, it will come with some ozone, which can be detected. Ozone has absorption bands in the infrared.
    - Oxygen plus methane together would be even more spectacular, as the combination would be outside of chemical equilibrium.

    This blog article predits 7 Earth-sized planets around TRAPPIST-1 - three are known already.
     
    Last edited: Feb 21, 2017
  2. jcsd
  3. Feb 21, 2017 #2
    Would looking for oxygen plus smog be too optimistic?
     
  4. Feb 21, 2017 #3

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Detecting industrial pollution in the atmospheres of earth-like exoplanets
    The exoplanets have to be really bad, even if we have the JWST available, to have detectable industrial pollution.

    A bit more sourced speculation about the press conference: 7 Earth-sized planets around TRAPPIST-1? 3 planets are known already, and the panel members were interested in follow-up observations if I interpret the blog sources correctly.

    This catalog of potentially habitable exoplanets expects an update on Thursday. Do they know something we do not?
     
  5. Feb 22, 2017 #4

    Ygggdrasil

    User Avatar
    Science Advisor

    Would oxygen be the main signature to indicate the possibility of life? Life existed on Earth for ~ 0.5 billion years before photosynthesis evolved (which began producing oxygen), and oxygen was not present in significant amounts in the atmosphere until about 2-2.5 billion years ago (for comparison, life is thought to have evolved ~ 4 billion years ago).
     
  6. Feb 22, 2017 #5

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Life has to alter the atmosphere notably to be detectable with current technology, there should be no natural process leading to the same result, and we need a way to find this gas. The introduction of oxygen is one of the best possibilities. Sure, not all life will emit oxygen, but life emitting CO2 won't be detectable as there are large natural sources of CO2.
     
  7. Feb 22, 2017 #6

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Yes, 7 planets around TRAPPIST-1, all about Earth-sized with quite precise radius estimates from transits, and approximate mass measurements from transit timing variation.

    3 are too hot for liquid water (b,c,d), 3 of them in the habitable zone (e,f,g), 1 (h) is too cold. The three planets seen before were the innermost two and the outermost one, so all potentially habitable planets are new. Probably tidally locked (all?).

    TRAPPIST-1e: ~0.92 times Earth radius, about half the mass
    f: missed the radius, but also similar to Earth
    g:1.05 times Earth radius, similar irradiation as Mars
    h: Largest planet. Period is poorly known which is odd.

    One has a density that suggests water present, but no confirmation of water yet. The orbits are in resonances, which suggests that they formed further out and migrated inwards, making water on them quite likely.

    Hubble is currently studying the atmospheres, and various other telescopes are looking at the system. JWST will do so later as well. JWST will measure the greenhouse gases to improve the temperature estimate, and it will look for oxygen/ozone and methane.
    We'll probably get good atmosphere estimates within the next 5 years.

    Ultracool dwarfs like TRAPPIST-1 start very active, could have blown away atmospheres from the planets in the past. Now (at least half a billion years old, hard to estimate better as the star doesn't change much any more) the star is very quiet.

    Moons around planets so close to the stars are unlikely. Tidal forces from other planets would be relevant. Planets as seen by other planets would look as large as the Moon from Earth.

    TRAPPIST program got extended to have more telescopes to observe more stars.
    SETI looked at the system in the past but didn't find anything.
     
    Last edited: Feb 22, 2017
  8. Feb 22, 2017 #7

    Ygggdrasil

    User Avatar
    Science Advisor

    From EurekaAlert press release:
    https://www.eurekalert.org/pub_releases/2017-02/e-uda022117.php\

    Here's the actual publication in Nature: Gillon et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542: 456 (2017). http://dx.doi.org/10.1038/nature21360[/URL]

    Abstract:
    [quote]One aim of modern astronomy is to detect temperate, Earth-like exoplanets that are well suited for atmospheric characterization. Recently, three Earth-sized planets were detected that transit (that is, pass in front of) a star with a mass just eight per cent that of the Sun, located 12 parsecs away[URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref1[/URL]. The transiting configuration of these planets, combined with the Jupiter-like size of their host star—named TRAPPIST-1—makes possible in-depth studies of their atmospheric properties with present-day and future astronomical facilities[URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref1[/URL], [URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref2[/URL], [URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref3[/URL]. Here we report the results of a photometric monitoring campaign of that star from the ground and space. Our observations reveal that at least seven planets with sizes and masses similar to those of Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain, such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.1 and 12.35 days) are near-ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inwards[URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref4[/URL], [URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref5[/URL]. Moreover, the seven planets have equilibrium temperatures low enough to make possible the presence of liquid water on their surfaces[URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref6[/URL], [URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref7[/URL], [URL]http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html#ref8[/URL].[/quote]

    Given that the planets are so close to the red dwarf, wouldn't the planets likely be tidally locked to the star? Seems similar to the case of [URL='https://www.physicsforums.com/threads/a-terrestrial-temperate-planet-around-proxima-centauri.882957/#post-5550240']Proxima b[/URL]
     
    Last edited by a moderator: May 8, 2017
  9. Feb 22, 2017 #8

    hilbert2

    User Avatar
    Science Advisor
    Gold Member

    If I understood it correctly, they don't have IR spectral data yet, so we have to wait a while before they can tell something about the chemical composition of the atmospheres.
     
  10. Feb 22, 2017 #9

    Haelfix

    User Avatar
    Science Advisor

    I wonder what the tidal forces would do for such a complicated system that are in such close proximity. The geological aspects would be fascinating. It's also not clear to me why people think they are all necessarily tidally locked.
     
  11. Feb 22, 2017 #10

    OmCheeto

    User Avatar
    Gold Member
    2016 Award

    Changing my will.

    NASA, ESA, et al, get everything. :oldlove:
     
  12. Feb 22, 2017 #11
    The announcement was really amazing! Seven earth-like planets around a single star!
    However, although they are located in the classical habitable zone, we need to be very cautious before calling them "habitable planets". The host star is not like our Sun and thus have some peculiarities. It is interesting to check these two papers about the Trappist system: Strong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1 and Water loss from terrestrial planets orbiting ultracool dwarfs: implications for the planets of TRAPPIST-1 .

    In short: the X-ray emission of Trappist-1 is strong enough that it could remove the atmosphere, or most of it, of the planets and also could evaporate their oceans.
     
  13. Feb 23, 2017 #12
    Two videos for us:

    1) NASA & TRAPPIST-1: A Treasure Trove of Planets Found (Feb 22, 2017)


    2) NASA full press conference on discovery of 7 Earth-like exoplanets (Feb 22, 2017)
     
  14. Feb 23, 2017 #13

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Concerning tidal effects: They scale with mass/(distance^3). That allows a comparison with the tidal effects of Moon. The largest tidal impact will be from (c) on (b), as they come closest: 30 times the tides Moon generates when they have their minimal distance. (b) will be too hot for global oceans, however. If we go further outwards: (e) and (f) have similar mass, and their maximal tidal effect is just 120% of the effect Moon has.
     
  15. Feb 23, 2017 #14
    It seems to me that this is not the first time found a planet similar to ours.
     
  16. Feb 23, 2017 #15
    I know a lot of white and red dwarf stars qualify as flare stars. Since Trappist -1 is an ultra cool dwarf, and as you've pointed out it quiets down with age, would this make flares less likely? In combination with the x-rays that have been mentioned, flare activity would not bode well for any "habitable zone" planet.
    Could one of these worlds possibly have a magnetic field strong enough to protect it from these issues, or is the x-ray radiation too powerful?
     
  17. Feb 23, 2017 #16

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    In the press conference they said the star is now very quiet, and they got a lot of telescope time to study potential atmospheres, so they certainly hope to find something.
    For exoplanets searches, planets like Venus and Mars are "similar" to Earth. By that metric, three of the TRAPPIST-1 planets are similar, and we have many others that are similar as well. Here are lists.
     
  18. Feb 23, 2017 #17

    Borg

    User Avatar
    Gold Member

    As I understand it, most (or all) of these planets are probably tidally locked. If there was liquid water on the warm side, wouldn't the water evaporate into the air, get blown to the dark side, precipitate out as snow and never get back to the other side? I guess you could get some melting on the fringes but I would think that the sunlit side would be pretty dry within a few million years at most.
     
  19. Feb 23, 2017 #18

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Hot gases from the sunlit side can heat the other side.
    Ice can move towards the sunlit side.

    Antarctica doesn't trap all the water on Earth either, and its temperature is constantly below zero.
     
  20. Feb 23, 2017 #19

    Borg

    User Avatar
    Gold Member

    I understand. I guess that it's more of an equilibrium question and Antarctica is a good example of equilibrium on our planet. I didn't think about an ocean near the fringes but I still wonder what the final equilibrium would be like.
     
  21. Feb 23, 2017 #20

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    We have Venus as interesting example. Its rotation is very slow (and retrograde), solar days are 116 Earth days long. Its atmosphere is so thick and moves so fast (in the upper layers) that the surface temperature does not change much during the day.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted