joigus Posted December 1, 2022 Posted December 1, 2022 This certainly sounds like a big deal: https://www.nature.com/articles/d41586-022-03820-3 5 papers published so far on it: References Rustamkulov, Z. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10487 (2022). Alderson, L. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10488 (2022). Ahrer, E.-M. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10489 (2022). Tsai, S.-M. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10490 (2022). Feinstein, A. D. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10493 (2022). But I would like to sample opinions from local experts. Some kind of photochemistry seems to be going on in the atmosphere of exoplanet GASP-39b The bulk of the information I've been able to gather so far is the presence of some mighty-selective absorption lines detected during the transient, and significant amounts of CO2 and SO2.
Ken Fabian Posted December 2, 2022 Posted December 2, 2022 I expect this type of observation and analysis of exoplanet atmosphere is the most likely way we will detect signs of life outside our solar system. Impressive to do so with a planet and star so far away. Not going to find life on this specific planet though, unless it is very different to life as we know it. And the method will be limited to planets that transit between the parent star and our solar system. I don't know if it could become possible to use more distant starlight that way, ie not confined to light from the parent star - seems unlikely, but not so long ago detecting any exoplanets seemed unlikely.
joigus Posted December 2, 2022 Author Posted December 2, 2022 10 hours ago, Ken Fabian said: I expect this type of observation and analysis of exoplanet atmosphere is the most likely way we will detect signs of life outside our solar system. Impressive to do so with a planet and star so far away. Not going to find life on this specific planet though, unless it is very different to life as we know it. I agree. If you think about the Earth from the point of view of external observers, and picture them looking at us only through a random time window, the most likely thing they would see would be a world ruled by cyanobacteria. Multicellular life came very late in the game. OTOH, inferring the existence of organisms like, say, an elephant only from chemical signatures seems far-fetched. So we may be seeing signatures of some life forms we have no idea what it may be, or its degree of complexity. It's also possible that some worls that potentially would harbour life, would find it impossible to get past the equivalent-to archean or proterozoic eons. It would be amazing to find them nonetheless. 10 hours ago, Ken Fabian said: I don't know if it could become possible to use more distant starlight that way, ie not confined to light from the parent star - seems unlikely, but not so long ago detecting any exoplanets seemed unlikely. Transits against more-distant stars? Do you think they could carry relevant chemical information?
Moontanman Posted December 2, 2022 Posted December 2, 2022 Isn't that planet so close to it's star that it makes Venus look like a ski resort?
joigus Posted December 2, 2022 Author Posted December 2, 2022 36 minutes ago, Moontanman said: Isn't that planet so close to it's star that it makes Venus look like a ski resort? Yes, it's about Jupiter-sized, but considerably lighter. And very close to its star. I don't know how it compares to Venus. Venus has a greenhouse effect on steroids, from what I remember. So maybe this one's milder and some kind of bacterial/archaean life can manage to pull some tricks. Who knows.
Moontanman Posted December 2, 2022 Posted December 2, 2022 1 hour ago, joigus said: Yes, it's about Jupiter-sized, but considerably lighter. And very close to its star. I don't know how it compares to Venus. Venus has a greenhouse effect on steroids, from what I remember. So maybe this one's milder and some kind of bacterial/archaean life can manage to pull some tricks. Who knows. Or possibly the "effect" is chemical and non biological?
joigus Posted December 2, 2022 Author Posted December 2, 2022 27 minutes ago, Moontanman said: Or possibly the "effect" is chemical and non biological? Sure. It's not that this photochemistry is necessarily related to biological activity. The finding is exciting nonetheless, because it allows planetary scientists to gather information on more varied scenarios of what kind of chemical processes might be going on out there. Here's a YT video on the find: https://www.youtube.com/watch?v=eW38rqLZMPg 1
exchemist Posted December 2, 2022 Posted December 2, 2022 19 hours ago, joigus said: This certainly sounds like a big deal: https://www.nature.com/articles/d41586-022-03820-3 5 papers published so far on it: References Rustamkulov, Z. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10487 (2022). Alderson, L. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10488 (2022). Ahrer, E.-M. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10489 (2022). Tsai, S.-M. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10490 (2022). Feinstein, A. D. et al. Preprint at arXiv https://doi.org/10.48550/arXiv.2211.10493 (2022). But I would like to sample opinions from local experts. Some kind of photochemistry seems to be going on in the atmosphere of exoplanet GASP-39b The bulk of the information I've been able to gather so far is the presence of some mighty-selective absorption lines detected during the transient, and significant amounts of CO2 and SO2. Interesting that there is so much water, considering the high temperatures - 900C- on the sunward side (it's tidally locked, apparently). One would think water would be lost into space at such temperatures, as the fraction of light molecules with velocity > escape velocity must be significant, I'd have thought. But then if, as they suggest, it started out in an orbit of similar radius to that of Jupiter, and was later kicked inward, we are probably not looking at an equilibrium state. 1
joigus Posted December 2, 2022 Author Posted December 2, 2022 35 minutes ago, exchemist said: But then if, as they suggest, it started out in an orbit of similar radius to that of Jupiter, and was later kicked inward, we are probably not looking at an equilibrium state. That makes sense. It's intriguing... I've read about exoplanets that are in a similar situation to what you suggest, and in some cases a trail has been identified as due to their atmosphere being lost from the exposure to the star's heat. I've just found this on Wikipedia, concerning another planet (51 Pegasi b) that's in a similar situation --tidally-locked gas giant very close to its star--, Quote In the report of the discovery, it was initially speculated that 51 Pegasi b [...], but it is now believed to be a gas giant. It is sufficiently massive that its thick atmosphere is not blown away by the star's solar wind. 51 Pegasi b probably has a greater radius than that of Jupiter despite its lower mass. This is because its superheated atmosphere must be puffed up into a thick but tenuous layer surrounding it. Beneath this, the gases that make up the planet would be so hot that the planet would glow red. Clouds of silicates may exist in the atmosphere. Why are experts so excited about SO2? --even more than by the presence of water or CO2.
Ken Fabian Posted December 2, 2022 Posted December 2, 2022 9 hours ago, joigus said: Transits against more-distant stars? Do you think they could carry relevant chemical information? I was thinking it is light source that passes through an exoplanet atmosphere too - ones that from our angle don't transit their parent star. It was a thought, but I hadn't thought it through - telescopes less good that that will probably be able to detect them and directly observe atmosphere lit by the parent star's light and get relevant chemical information from it. 1
joigus Posted December 3, 2022 Author Posted December 3, 2022 16 hours ago, Ken Fabian said: I was thinking it is light source that passes through an exoplanet atmosphere too - ones that from our angle don't transit their parent star. It was a thought, but I hadn't thought it through - telescopes less good that that will probably be able to detect them and directly observe atmosphere lit by the parent star's light and get relevant chemical information from it. I see. Just off the top of my head, apart from resolution --as you said--, it seems hard to identify telltale signs of a planetary transit, as such events wouldn't have any definite transit period. But who knows. I find this conversation stimulating. Just as I was pondering about your comments, I've started wondering about rogue planets. It seems to me that detecting them would be similar to what you're suggesting. They obviously have no neighbour star to transit against. There is a mention of microlensing techniques in relation to a possible detection on this Wikipedia article: https://en.wikipedia.org/wiki/Rogue_planet#:~:text=A rogue planet (also termed,without a host planetary system. Quote In September 2020, astronomers using microlensing techniques reported the detection, for the first time, of an Earth-mass rogue planet (named OGLE-2016-BLG-1928) unbounded to any star and free floating in the Milky Way galaxy.[19][20][21] They're based on gravitational lensing. Gravitation lensing doesn't afford you the possibility of getting data about the chemistry. But combined techniques could do it. I could be totally wrong, as I'm very far from having any level of expertise on this.
exchemist Posted December 3, 2022 Posted December 3, 2022 (edited) 19 hours ago, joigus said: That makes sense. It's intriguing... I've read about exoplanets that are in a similar situation to what you suggest, and in some cases a trail has been identified as due to their atmosphere being lost from the exposure to the star's heat. I've just found this on Wikipedia, concerning another planet (51 Pegasi b) that's in a similar situation --tidally-locked gas giant very close to its star--, Why are experts so excited about SO2? --even more than by the presence of water or CO2. Doing some back of the envelope calculations, the rms velocity of water molecules at 900C will be about 1.26km/sec, if I've got my arithmetic right. (v[rms] = √(3RT/m) m being in kg. ) The escape velocity of Saturn, which has about the same mass as this planet, would be 36km/sec. I have not worked out how to do the velocity distribution curve, to see what fraction of the "tail" of the velocity curve will represent molecules with a velocity greater than this, but one can see it could easily be 0.1-1% or so. So one might expect the water to escape over time. Regarding SO2 I'm not sure I follow this, except that one might expect reducing conditions, in which case the presence of SO2 rather than H2S presumably indicates photochemical reactions. They propose photolysis of water, apparently. Edited December 3, 2022 by exchemist 1
Moontanman Posted December 3, 2022 Posted December 3, 2022 1 hour ago, joigus said: I see. Just off the top of my head, apart from resolution --as you said--, it seems hard to identify telltale signs of a planetary transit, as such events wouldn't have any definite transit period. But who knows. I find this conversation stimulating. Just as I was pondering about your comments, I've started wondering about rogue planets. It seems to me that detecting them would be similar to what you're suggesting. They obviously have no neighbour star to transit against. There is a mention of microlensing techniques in relation to a possible detection on this Wikipedia article: https://en.wikipedia.org/wiki/Rogue_planet#:~:text=A rogue planet (also termed,without a host planetary system. They're based on gravitational lensing. Gravitation lensing doesn't afford you the possibility of getting data about the chemistry. But combined techniques could do it. I could be totally wrong, as I'm very far from having any level of expertise on this. Rogue planets are fascinating, Especially rocky planets with dense hydrogen atmospheres could actually harbor life with water oceans and dry land. Sara Seager of NASA has proposed this. 1
joigus Posted December 3, 2022 Author Posted December 3, 2022 (edited) 5 hours ago, exchemist said: Doing some back of the envelope calculations, the rms velocity of water molecules at 900C will be about 1.26km/sec, if I've got my arithmetic right. (v[rms] = √(3RT/m) m being in kg. ) The escape velocity of Saturn, which has about the same mass as this planet, would be 36km/sec. I have not worked out how to do the velocity distribution curve, to see what fraction of the "tail" of the velocity curve will represent molecules with a velocity greater than this, but one can see it could easily be 0.1-1% or so. So one might expect the water to escape over time. Thanks! I used \( \sqrt{2K_B T / m} \) with Boltzmann's constant. The ballpark of it certainly checks with me. Your argument seems convincing, and very informative. +1 We sometimes forget the cosmic time scales. We see Saturn in the sky with its beautiful rings and it isn't a static situation. Probably the aftermath of a catastrophe as compared to Solar-system lifetime. Similarly, it's very likely that this giant got sucked into the inner region from a recent event --in terms of the age of that star system. 5 hours ago, Moontanman said: Rogue planets are fascinating, Especially rocky planets with dense hydrogen atmospheres could actually harbor life with water oceans and dry land. Sara Seager of NASA has proposed this. I sometimes fantasize with the possibilities they offer. I don't think it's too far-fetched that a select group of them can seed other systems with life. Edited December 3, 2022 by joigus 1
exchemist Posted December 4, 2022 Posted December 4, 2022 17 hours ago, joigus said: Thanks! I used 2KBT/m−−−−−−−−√ with Boltzmann's constant. The ballpark of it certainly checks with me. Your argument seems convincing, and very informative. +1 We sometimes forget the cosmic time scales. We see Saturn in the sky with its beautiful rings and it isn't a static situation. Probably the aftermath of a catastrophe as compared to Solar-system lifetime. Similarly, it's very likely that this giant got sucked into the inner region from a recent event --in terms of the age of that star system. I sometimes fantasize with the possibilities they offer. I don't think it's too far-fetched that a select group of them can seed other systems with life. Actually, on further reflection, if @Janus were here he'd probably be telling me I'm going about this all wrong and that the real mechanism of depletion is the stripping action of the solar wind on the outer atmosphere (ionosphere?), like the way a diffusion pump works.
joigus Posted December 4, 2022 Author Posted December 4, 2022 1 hour ago, exchemist said: Actually, on further reflection, if @Janus were here he'd probably be telling me I'm going about this all wrong and that the real mechanism of depletion is the stripping action of the solar wind on the outer atmosphere (ionosphere?), like the way a diffusion pump works. I see. Depletion is more to do with solar wind, so the momentum of protons hitting the atmosphere is essential. I also think this thread requires an expert to guide it through.
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