The headline, as usual, plays up the research, which is primarily about establishing that a single planet, TRAPPIST-1c, has no atmosphere. But the research methodology is actually quite a bit more...
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The headline, as usual, plays up the research, which is primarily about establishing that a single planet, TRAPPIST-1c, has no atmosphere. But the research methodology is actually quite a bit more interesting than the headline.
The journal article summarized by the link is here. I'm not a specialist, but I was interested and did some work to grasp the main ideas, which I'll try to summarize here for anyone else who wants to go deeper.
TRAPPIST-1 is a dwarf star about 40 light years away. That's quite close in interstellar terms, which makes it easy to observe.
TRAPPIST-1 has seven planets. The planet of interest to this study, TRAPPIST-1c, orbits its star once every 2.4 days and is about the radius of the Earth. So everything is much more compact than the solar system we live in.
In part because TRAPPIST-1c is so close to its sun, it is tidally locked, which means that one side of it always faces its sun. (Our moon is also tidally locked to the Earth, which is why we never see its back side.)
Therefore, the side of TRAPPIST-1c that faces its sun is expected to be much hotter than the side that faces away - unless there is some sort of atmosphere which would act to spread out the heat. This is the fulcrum that the study leans on to come to its conclusion.
Now, we can begin to unpack the abstract:
We measure a planet-to-star flux ratio of fp/f⁎ = 421 ± 94 parts per million (ppm), which corresponds to an inferred dayside brightness temperature of 380 ± 31 K. This high dayside temperature disfavours a thick, CO2-rich atmosphere on the planet.
This makes sense now: If there were atmosphere, the dayside (facing the sun) would not be so hot. But how did they figure out how hot the atmosphere is, and what does that have to do with eclipses?
The key is in the term "planet-to-star flux ratio". Flux refers to how much energy passes through a particular area (e.g. a telescope's lens) per unit time. Brightness, basically. When the planet TRAPPIST-1c passes behind its star, for a moment, its light is blocked out by the star and the brightness of the entire system dims. This figure shows a red curve which models the brightness of the system during these eclipses. Notice the red curve sits at a y-coordinate of about 400 except for the eclipse dip? That 400-ish number is the planet-to-star flux ratio. It's just a way of saying "this is how much the light dims when the planet goes behind the star".
Hotter planets give off more flux. So the amount of dimming during eclipses gives the researchers a way to infer the temperature of the planet. (And since no light comes from its dark side, we know the flux is caused by its dayside, which is the part we're trying to measure!) This is how they conclude the temperature is about 380 K.
Then they rule out the likelihood of a thick atmosphere by comparing these results to a bunch of models and simulations and showing that they do not match up with the simulations where there is an atmosphere but they are consistent with bare rock.
Whew. And that's the research. Again, not a specialist, so take all of this with a cupful of salt, but I hope it's interesting!
Thank you for dissecting the research and explaining it in such an understandable way! Really interesting. The original article posted says “ TRAPPIST-1 c’s surface temperature, on the side that...
Thank you for dissecting the research and explaining it in such an understandable way! Really interesting.
The original article posted says “ TRAPPIST-1 c’s surface temperature, on the side that faces its star, registers at around 107 °C — too hot to maintain a thick atmosphere that is rich in carbon dioxide.” This feels like a much simpler question than everything you parsed out here so I thought I’d try asking you: why does heat = no atmosphere?
I have to agree it's likely, but it's beyond a scale with winning Powerball. I also have to accept that our ability to live in our habitat is specialized. Even at the fringes we require tools to...
I have to agree it's likely, but it's beyond a scale with winning Powerball.
I also have to accept that our ability to live in our habitat is specialized. Even at the fringes we require tools to survive in the short term, and adaptations (and their required timeframes to develop) to survive long term. The odds of finding something out there are slim enough, and then of course the vast distance requiring literal generations (reproduction during the course would likely be a constraint) in order to transport. It's a tall order, and fixing our sitch here remains to be the most efficient solution. Alas, humans are a selfish lot.
I don’t agree that looking for “backup” environments is taking focus away from preserving the Earth. Only a small percentage of interest and resources are spent worrying about that. Pollution,...
I don’t agree that looking for “backup” environments is taking focus away from preserving the Earth. Only a small percentage of interest and resources are spent worrying about that.
Pollution, war, and petroleum consumption are a far greater risk to our survival.
Also religious fanatics that assume there is another world waiting for them if we blow up this one.
I sigh whenever people talk about settling or terraforming other worlds. We can't even be bothered to keep our own homeworld terraformed, yet we're going to muster the political and societal will...
I sigh whenever people talk about settling or terraforming other worlds. We can't even be bothered to keep our own homeworld terraformed, yet we're going to muster the political and societal will to start a project magnitudes more expensive and difficult, and whose completion will arrive generations after its beginning? It's just pure fantasy. We can't even get ourselves to go to Mars, and it's right there.
Life requires chemistry, and chemistry achieves by far its maximum potential when there's carbon and liquid water around. That's peak chemistry with peak chemical versatility. The places where...
Life requires chemistry, and chemistry achieves by far its maximum potential when there's carbon and liquid water around. That's peak chemistry with peak chemical versatility. The places where liquid water exists are just by chemical potential more likely to have advanced life than places where it does not.
There are for example theories about silicon life that show it's possible, but compared to carbon life it's limited and slow moving, meaning slower evolution. Far fewer chemical tricks it can play with than carbon. We're not likely to find life on a star because the chemistry there is just too volatile. It's all a probabilities game. That's why we look for liquid water - those environments have the highest chances in the raw physics for other life to exist and be looking back at us. We have to target our limited telescope time so that's where it goes.
Unless its more probable for life to evolve on a non-earth like planet, the fact that we see so no earth-like planets and we see no life on any non-earth like planets is evidence that life isn't...
Unless its more probable for life to evolve on a non-earth like planet, the fact that we see so no earth-like planets and we see no life on any non-earth like planets is evidence that life isn't common.
All arguments I've seen to date suggest that carbon based life is the only *probable type of life.
This is pretty amazing stuff to read. We’ve gone from “we can look for blips to find stars with exoplanets” to “this specific system has 7 known planets, and we’re going to look at the atmosphere...
This is pretty amazing stuff to read. We’ve gone from “we can look for blips to find stars with exoplanets” to “this specific system has 7 known planets, and we’re going to look at the atmosphere makeup of them one by one”. The level of detail were starting to unlock really let’s us explore the galaxy.
The headline, as usual, plays up the research, which is primarily about establishing that a single planet, TRAPPIST-1c, has no atmosphere. But the research methodology is actually quite a bit more interesting than the headline.
The journal article summarized by the link is here. I'm not a specialist, but I was interested and did some work to grasp the main ideas, which I'll try to summarize here for anyone else who wants to go deeper.
Now, we can begin to unpack the abstract:
This makes sense now: If there were atmosphere, the dayside (facing the sun) would not be so hot. But how did they figure out how hot the atmosphere is, and what does that have to do with eclipses?
The key is in the term "planet-to-star flux ratio". Flux refers to how much energy passes through a particular area (e.g. a telescope's lens) per unit time. Brightness, basically. When the planet TRAPPIST-1c passes behind its star, for a moment, its light is blocked out by the star and the brightness of the entire system dims. This figure shows a red curve which models the brightness of the system during these eclipses. Notice the red curve sits at a y-coordinate of about 400 except for the eclipse dip? That 400-ish number is the planet-to-star flux ratio. It's just a way of saying "this is how much the light dims when the planet goes behind the star".
Hotter planets give off more flux. So the amount of dimming during eclipses gives the researchers a way to infer the temperature of the planet. (And since no light comes from its dark side, we know the flux is caused by its dayside, which is the part we're trying to measure!) This is how they conclude the temperature is about 380 K.
Then they rule out the likelihood of a thick atmosphere by comparing these results to a bunch of models and simulations and showing that they do not match up with the simulations where there is an atmosphere but they are consistent with bare rock.
Whew. And that's the research. Again, not a specialist, so take all of this with a cupful of salt, but I hope it's interesting!
Thank you for dissecting the research and explaining it in such an understandable way! Really interesting.
The original article posted says “ TRAPPIST-1 c’s surface temperature, on the side that faces its star, registers at around 107 °C — too hot to maintain a thick atmosphere that is rich in carbon dioxide.” This feels like a much simpler question than everything you parsed out here so I thought I’d try asking you: why does heat = no atmosphere?
I have to agree it's likely, but it's beyond a scale with winning Powerball.
I also have to accept that our ability to live in our habitat is specialized. Even at the fringes we require tools to survive in the short term, and adaptations (and their required timeframes to develop) to survive long term. The odds of finding something out there are slim enough, and then of course the vast distance requiring literal generations (reproduction during the course would likely be a constraint) in order to transport. It's a tall order, and fixing our sitch here remains to be the most efficient solution. Alas, humans are a selfish lot.
I don’t agree that looking for “backup” environments is taking focus away from preserving the Earth. Only a small percentage of interest and resources are spent worrying about that.
Pollution, war, and petroleum consumption are a far greater risk to our survival.
Also religious fanatics that assume there is another world waiting for them if we blow up this one.
I sigh whenever people talk about settling or terraforming other worlds. We can't even be bothered to keep our own homeworld terraformed, yet we're going to muster the political and societal will to start a project magnitudes more expensive and difficult, and whose completion will arrive generations after its beginning? It's just pure fantasy. We can't even get ourselves to go to Mars, and it's right there.
Life requires chemistry, and chemistry achieves by far its maximum potential when there's carbon and liquid water around. That's peak chemistry with peak chemical versatility. The places where liquid water exists are just by chemical potential more likely to have advanced life than places where it does not.
There are for example theories about silicon life that show it's possible, but compared to carbon life it's limited and slow moving, meaning slower evolution. Far fewer chemical tricks it can play with than carbon. We're not likely to find life on a star because the chemistry there is just too volatile. It's all a probabilities game. That's why we look for liquid water - those environments have the highest chances in the raw physics for other life to exist and be looking back at us. We have to target our limited telescope time so that's where it goes.
There likely is life on other (habitable) planets, but nothing more complex then an algae analogue.
Unless its more probable for life to evolve on a non-earth like planet, the fact that we see so no earth-like planets and we see no life on any non-earth like planets is evidence that life isn't common.
All arguments I've seen to date suggest that carbon based life is the only *probable type of life.
If this is true and all the life out there is desperately looking for planets like their own and finding jack shit, it's weirdly poetic.
This is pretty amazing stuff to read. We’ve gone from “we can look for blips to find stars with exoplanets” to “this specific system has 7 known planets, and we’re going to look at the atmosphere makeup of them one by one”. The level of detail were starting to unlock really let’s us explore the galaxy.