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Some caveats per Marina Koren https://twitter.com/marinakoren/status/1171873631808438273 https://twitter.com/marinakoren/status/1171873631808438273 1. This pla

Some caveats per Marina Koren https://twitter.com/marinakoren/status/1171873631808438273 https://twitter.com/marinakoren/status/1171873631808438273 1. This planet probably doesn’t have a solid surface 2. Being in the “habitable zone” doesn’t mean a planet is habitable 3. The detection is of water molecules, chances are the water only exists as vapour in the atmosphere of this small gas giant. 4. If you ask 10 astronomers about this you will get 11 opinions

mabbo 7y ago
Years ago as a second year computer science student, I mentioned to a grad student I knew how disappointed I was about a certain algorithm. "It's O(n), but the constant is enormous! There's no point unless you have billions of elements"! She said to me "Yeah sure, but who cares? What it really tells us it's that it's possible to do this in linear time at all. That might not have been true, and now we know we might find a faster linear algorithm." (All of this is paraphrased because it's been over a decade). The point is: we have found another planet with water. We now know this is possible! We know that it's probably not super uncommon (or else we wouldn't have found one so soon). That's what's amazing about this. So what if it's not perfect, it's a great discovery!
- ant6n 7y ago
  We already knew it's possible to have a planet in the habitable zone with water (and life, incidentally). Whether it's common is still unclear, given that so far there's a big bias towards detecting large exoplanets that are close to the host star.
  - saagarjha 7y ago
    The point is finding planets aside from our own.
    - solipsism 7y ago
      Sometimes N=2 is extremely different from N=1. Specifically when we have N=1 and we suspect that it might be unique, or extremely rare to the point that you wouldn't expect to find instances. Sometimes N=2 is not that different from N=1 though. Specifically when you don't think the situation is necessarily that rare, you just don't have a big population to choose from. That's the situation here. Astronomers expect to find other Earth-like planets. We suspect rocky planets aren't that rare, we know planets at comparable distances from the star are not that rare, and we know H20 is plentiful in space. The problem is one of detection. The smaller the planet, the harder it is to detect water, so most of what we've found so far is gassy giants. A good analogy is the fact that I don't know anyone who shares my birthday. That doesn't mean I would be amazed if I were to find someone did share my birthday, cuz I have no reason to suspect my birthday is particularly rare. I just don't know that many people.
      - deleted 7y ago
        [deleted]
      - dodobirdlord 7y ago
        In this case N=2 is very different from N=1. The probability of detecting further Earth-like planets is not influenced by the existence of Earth, because what we're actually measuring is the conditional probability of detecting Earth-like planets given the existence of Earth, which already factors Earth in. In this case N=1 is a lot more like N=0 and N=2 is a lot more like N=1.
        solipsism 7y ago
        That's silly. The type of world we're interested in is ones that could support life as we know it. We knew one of those exists. We're trying to find more.
        dodobirdlord 7y ago
        Calling it silly seems a bit harsh, it's just statistics. We are interested in knowing the frequency of earth-like planets existing. If we assume that the existence of earth is a pre-condition for life existing and performing the measurement, then the existence of earth tells us nothing about that frequency. Regardless of the frequency in question the count of earth-like planets starts at 1, because in scenarios where the count is at 0 the measurement is not being performed. There could be millions of earth-like planets in the milky way, or there could be only one, or earth could even be the only life-supporting planet in the universe. There is no mechanism given only the existence of earth to reason statistically about the distribution of earth-like planets. Whereas finding a second one tells us a lot. So that's why I say we are in more like the N=0 case, and that finding a second earth-like planet puts us in the N=1 case.
caf 7y ago
I am amused by the idea of a "small giant".
- mr_toad 7y ago
  Neptune is ‘only’ 57 times the volume of Earth, whereas Jupiter is 1321 times the volume of Earth. The size range of ice/gas giants is bigger than the gap between Earth and the smallest ice giants.
  - Stratoscope 7y ago
    Does it make sense to compare both Neptune and Jupiter to the Earth? I would think the relative numbers for each pair are a more useful comparison. If Neptune is 57 times the volume of Earth and Jupiter is 1321 times the volume of Earth, then Jupiter is 23 times the volume of Neptune. So the relative difference between Neptune and Jupiter is less than half the relative difference between Earth and Neptune. As another illustration, let's take a different trio of objects: a golf ball, the Moon, and the Earth. Using very round numbers, it is safe to say that the volume of the Moon is about one zillion golf balls. The Earth is about 50 times the volume of the Moon, so the Earth is 50 zillion golf balls. Clearly, the difference between 50 zillion and 1 zillion is much greater than the difference between 1 zillion and just 1 golf ball, by a factor of nearly 50. Or is it? If you ask anyone on the street, they won't have to calculate anything, they will tell you that the Earth and Moon are much more similar in size than the Moon and a golf ball. That's because they are using relative sizes, not absolute.
brownbat 7y ago
> Being in the “habitable zone” doesn’t mean a planet is habitable True. Being a spooky near twin of Earth isn't necessarily enough. The air inside popcorn factories is basically identical to the Earth's atmosphere, but breathing in diacetyl, a butter flavor you'll find in that air, will kill you a few months or years later. Popcorn lung really undermined my naive view that we would one day be able to run a scan or a sniff test on a planet and then just breathe without assistance. https://en.wikipedia.org/wiki/Bronchiolitis_obliterans https://en.wikipedia.org/wiki/Bronchiolitis_obliterans You have an identical twin to Earth with slightly different dust composition and it could shred our lungs. We are highly, highly tuned to our home. Which doesn't mean we can't go anywhere. But it won't just be advances in travel speed that will get us off world. It may also require drastic modifications to the human organism.
- deleted 7y ago
  [deleted]
- tripzilch 7y ago
  That'd be something, people travel for 30 years to a distant planet, die four days later because something in the atmosphere we didn't account for and did not filter properly, or a crystalline fungus that eats away our suits.
  - perl4ever 7y ago
    Happens a lot in (bad) science fiction, and parody thereof. People land on a planet, go "I wonder if the atmosphere is breathable?", then open their helmet and take a deep breath. But I think by the time anyone is arriving on a planet around another star, it will be with biotechnology that allows adaptation to a rather wide variety of environments.
petre 7y ago
It isn't habitable even if it's a super Earth because the gravity would be 8g if it's 8x the mass of Earth.
- BurningFrog 7y ago
  That's not how it works. The moon is 1% of Earth's mass, but has 16% of our gravity. I'm not entirely clear on the deciding factors, but it's probably mostly density.
  - saberdancer 7y ago
    It depends on the mass of the planet and the diameter. Since planets are usually sphere shaped, it effectively means that the gravity grows with diameter (for same density) and vice versa (for same diameter, grows if density grows). Moon is about 4 times smaller (for same density, gravity would be about 4 times smaller) but Moon has lower density as well (about 60% of Earth) so it comes down to those 16%. Rough napkin formulas below. Apologies for formatting) F=ma F(g) = GMm/(r^2) ma=GMm/(r^2) a=GM/r^2 Volume of a sphere = (4/3)pir^3 mass of a planet = density volume M=ro(4/3)pir^3 a=(Gro(4/3)pir^3)/r^2 a=Gro(4/3)pi*r given that G, 4/3 and pi are constants, it comes just to density multiplied with diameter.
  - Anarch157a 7y ago
    Higher density allows the surface to be closer to the center of mass, so the gravity there will be higher. Stand on a hovering platform 6300km from the Moons center and the gravity will be just 1% of Earths, since distance beeing equal, the only deciding factor will be the mass. That's why the gravity on the surface of neutron stars is so high, even when the mass is the same as our Sun.
    - perl4ever 7y ago
      The earth doesn't have uniform density at all depths - not sure about the moon. I forget exactly, but I was just reading about how if you could travel to the earth's core, because the density increases a lot, you would continue to experience around 1G something like halfway to the center.
aussieguy1234 7y ago
I think the keyword here is "potentially habitable"
luxuryballs 7y ago
Also it just seems to be water, they’re obviously not 100% sure it’s not something else that’s reading as water.
- gmueckl 7y ago
  How easy is it to have different mixtures of substances that lead to similar enough absorption apectra that they are indistinguishable with the available resolution and sensitivity?
  - ianai 7y ago
    Not very.
  - luxuryballs 7y ago
    There’s no reason I can see to assume we’ve discovered even 1% of the elements out there... we’re also just seeing a trace of something that was there hundreds of years ago right? We’ve never even gone out there to see if our assumption that only water cause this kind of reflected light is even correct.
Tepix 7y ago
> 2. Being in the “habitable zone” doesn’t mean a planet is habitable Related question: Does "habitable" mean "habitable for humans"? I thought it didn't, but after reading some dictionary definitions, i believe it does. On the other hand looking at the planetary habitability wikipedia page it's clear that it means "life-friendly". No wonder many people are confused. Of course a planet with 8-9 times the mass of earth is not very friendly for humans, ignoring all the other possible issues (pressure, chemical composition, radiation, flares etc)
- manicdee 7y ago
  The “habitable zone” is the theoretical range from the Star that allows an Earth-like planet to have mean temperatures suitable for Earth-like life. It’s almost entirely arbitrary, but roughly based on luminosity of the star.
- perl4ever 7y ago
  People have commented that a planet a bit larger than earth (I think 8-9 times qualifies) would have gravity too strong for rockets to ever be practical, and thus whether you were a marooned earthling or evolved there, you would never ever be able to get into orbit. So, there could be "super-earths" with life similar to ours, even intelligent, and they would never be able to participate in a space-faring society.
  - Tepix 7y ago
    Never? What if you build a spaceline moon elevator on their moon and dangle it into their gravity well to assist them...

mabbo 7y ago

Years ago as a second year computer science student, I mentioned to a grad student I knew how disappointed I was about a certain algorithm. "It's O(n), but the constant is enormous! There's no point unless you have billions of elements"! She said to me "Yeah sure, but who cares? What it really tells us it's that it's possible to do this in linear time at all. That might not have been true, and now we know we might find a faster linear algorithm." (All of this is paraphrased because it's been over a decade). The point is: we have found another planet with water. We now know this is possible! We know that it's probably not super uncommon (or else we wouldn't have found one so soon). That's what's amazing about this. So what if it's not perfect, it's a great discovery!

ant6n 7y ago
We already knew it's possible to have a planet in the habitable zone with water (and life, incidentally). Whether it's common is still unclear, given that so far there's a big bias towards detecting large exoplanets that are close to the host star.
- saagarjha 7y ago
  The point is finding planets aside from our own.
  - solipsism 7y ago
    Sometimes N=2 is extremely different from N=1. Specifically when we have N=1 and we suspect that it might be unique, or extremely rare to the point that you wouldn't expect to find instances. Sometimes N=2 is not that different from N=1 though. Specifically when you don't think the situation is necessarily that rare, you just don't have a big population to choose from. That's the situation here. Astronomers expect to find other Earth-like planets. We suspect rocky planets aren't that rare, we know planets at comparable distances from the star are not that rare, and we know H20 is plentiful in space. The problem is one of detection. The smaller the planet, the harder it is to detect water, so most of what we've found so far is gassy giants. A good analogy is the fact that I don't know anyone who shares my birthday. That doesn't mean I would be amazed if I were to find someone did share my birthday, cuz I have no reason to suspect my birthday is particularly rare. I just don't know that many people.
    - deleted 7y ago
      [deleted]
    - dodobirdlord 7y ago
      In this case N=2 is very different from N=1. The probability of detecting further Earth-like planets is not influenced by the existence of Earth, because what we're actually measuring is the conditional probability of detecting Earth-like planets given the existence of Earth, which already factors Earth in. In this case N=1 is a lot more like N=0 and N=2 is a lot more like N=1.
      - solipsism 7y ago
        That's silly. The type of world we're interested in is ones that could support life as we know it. We knew one of those exists. We're trying to find more.
        dodobirdlord 7y ago
        Calling it silly seems a bit harsh, it's just statistics. We are interested in knowing the frequency of earth-like planets existing. If we assume that the existence of earth is a pre-condition for life existing and performing the measurement, then the existence of earth tells us nothing about that frequency. Regardless of the frequency in question the count of earth-like planets starts at 1, because in scenarios where the count is at 0 the measurement is not being performed. There could be millions of earth-like planets in the milky way, or there could be only one, or earth could even be the only life-supporting planet in the universe. There is no mechanism given only the existence of earth to reason statistically about the distribution of earth-like planets. Whereas finding a second one tells us a lot. So that's why I say we are in more like the N=0 case, and that finding a second earth-like planet puts us in the N=1 case.

caf 7y ago

I am amused by the idea of a "small giant".

mr_toad 7y ago
Neptune is ‘only’ 57 times the volume of Earth, whereas Jupiter is 1321 times the volume of Earth. The size range of ice/gas giants is bigger than the gap between Earth and the smallest ice giants.
- Stratoscope 7y ago
  Does it make sense to compare both Neptune and Jupiter to the Earth? I would think the relative numbers for each pair are a more useful comparison. If Neptune is 57 times the volume of Earth and Jupiter is 1321 times the volume of Earth, then Jupiter is 23 times the volume of Neptune. So the relative difference between Neptune and Jupiter is less than half the relative difference between Earth and Neptune. As another illustration, let's take a different trio of objects: a golf ball, the Moon, and the Earth. Using very round numbers, it is safe to say that the volume of the Moon is about one zillion golf balls. The Earth is about 50 times the volume of the Moon, so the Earth is 50 zillion golf balls. Clearly, the difference between 50 zillion and 1 zillion is much greater than the difference between 1 zillion and just 1 golf ball, by a factor of nearly 50. Or is it? If you ask anyone on the street, they won't have to calculate anything, they will tell you that the Earth and Moon are much more similar in size than the Moon and a golf ball. That's because they are using relative sizes, not absolute.

brownbat 7y ago

> Being in the “habitable zone” doesn’t mean a planet is habitable True. Being a spooky near twin of Earth isn't necessarily enough. The air inside popcorn factories is basically identical to the Earth's atmosphere, but breathing in diacetyl, a butter flavor you'll find in that air, will kill you a few months or years later. Popcorn lung really undermined my naive view that we would one day be able to run a scan or a sniff test on a planet and then just breathe without assistance. https://en.wikipedia.org/wiki/Bronchiolitis_obliterans https://en.wikipedia.org/wiki/Bronchiolitis_obliterans You have an identical twin to Earth with slightly different dust composition and it could shred our lungs. We are highly, highly tuned to our home. Which doesn't mean we can't go anywhere. But it won't just be advances in travel speed that will get us off world. It may also require drastic modifications to the human organism.

deleted 7y ago
[deleted]
tripzilch 7y ago
That'd be something, people travel for 30 years to a distant planet, die four days later because something in the atmosphere we didn't account for and did not filter properly, or a crystalline fungus that eats away our suits.
- perl4ever 7y ago
  Happens a lot in (bad) science fiction, and parody thereof. People land on a planet, go "I wonder if the atmosphere is breathable?", then open their helmet and take a deep breath. But I think by the time anyone is arriving on a planet around another star, it will be with biotechnology that allows adaptation to a rather wide variety of environments.

petre 7y ago

It isn't habitable even if it's a super Earth because the gravity would be 8g if it's 8x the mass of Earth.

BurningFrog 7y ago
That's not how it works. The moon is 1% of Earth's mass, but has 16% of our gravity. I'm not entirely clear on the deciding factors, but it's probably mostly density.
- saberdancer 7y ago
  It depends on the mass of the planet and the diameter. Since planets are usually sphere shaped, it effectively means that the gravity grows with diameter (for same density) and vice versa (for same diameter, grows if density grows). Moon is about 4 times smaller (for same density, gravity would be about 4 times smaller) but Moon has lower density as well (about 60% of Earth) so it comes down to those 16%. Rough napkin formulas below. Apologies for formatting) F=ma F(g) = GMm/(r^2) ma=GMm/(r^2) a=GM/r^2 Volume of a sphere = (4/3)pir^3 mass of a planet = density volume M=ro(4/3)pir^3 a=(Gro(4/3)pir^3)/r^2 a=Gro(4/3)pi*r given that G, 4/3 and pi are constants, it comes just to density multiplied with diameter.
- Anarch157a 7y ago
  Higher density allows the surface to be closer to the center of mass, so the gravity there will be higher. Stand on a hovering platform 6300km from the Moons center and the gravity will be just 1% of Earths, since distance beeing equal, the only deciding factor will be the mass. That's why the gravity on the surface of neutron stars is so high, even when the mass is the same as our Sun.
  - perl4ever 7y ago
    The earth doesn't have uniform density at all depths - not sure about the moon. I forget exactly, but I was just reading about how if you could travel to the earth's core, because the density increases a lot, you would continue to experience around 1G something like halfway to the center.

aussieguy1234 7y ago

I think the keyword here is "potentially habitable"

luxuryballs 7y ago

Also it just seems to be water, they’re obviously not 100% sure it’s not something else that’s reading as water.

gmueckl 7y ago
How easy is it to have different mixtures of substances that lead to similar enough absorption apectra that they are indistinguishable with the available resolution and sensitivity?
- ianai 7y ago
  Not very.
- luxuryballs 7y ago
  There’s no reason I can see to assume we’ve discovered even 1% of the elements out there... we’re also just seeing a trace of something that was there hundreds of years ago right? We’ve never even gone out there to see if our assumption that only water cause this kind of reflected light is even correct.

Tepix 7y ago

> 2. Being in the “habitable zone” doesn’t mean a planet is habitable Related question: Does "habitable" mean "habitable for humans"? I thought it didn't, but after reading some dictionary definitions, i believe it does. On the other hand looking at the planetary habitability wikipedia page it's clear that it means "life-friendly". No wonder many people are confused. Of course a planet with 8-9 times the mass of earth is not very friendly for humans, ignoring all the other possible issues (pressure, chemical composition, radiation, flares etc)

manicdee 7y ago
The “habitable zone” is the theoretical range from the Star that allows an Earth-like planet to have mean temperatures suitable for Earth-like life. It’s almost entirely arbitrary, but roughly based on luminosity of the star.
perl4ever 7y ago
People have commented that a planet a bit larger than earth (I think 8-9 times qualifies) would have gravity too strong for rockets to ever be practical, and thus whether you were a marooned earthling or evolved there, you would never ever be able to get into orbit. So, there could be "super-earths" with life similar to ours, even intelligent, and they would never be able to participate in a space-faring society.
- Tepix 7y ago
  Never? What if you build a spaceline moon elevator on their moon and dangle it into their gravity well to assist them...