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NASA gets it right.
May. 22nd, 2016 10:08 pmNASA recently announced that the kepler mission had found a big whack of exo-solar planets. some of them are even the habitable zone™ of stars, even though we really don't know what we mean by that¹.
usually, these announcements are accompanied by pretty pictures showing earthlike planets with atmospheres, seas, and clouds. unfortunately for science, we don't actually know any of that². all we know about these planets is an estimate of their orbital period, which gives us an estimate of their distances from their stars, and a guess about how big they are. that's it. no air, much less seas and clouds and other features indicating people will eventually be able to start new lives in the off-world colonies.
so i'm insanely pleased that NASA is running a scientifically accurate picture of what we know:
and it's a very information-dense image too: not only does it show the planets' orbits and sizes, it provides comparisons of those to venus, earth, and mars; it tells us about the color of the stars they orbit; and even whether what we're looking at was just reported or old news. be still, my geeky heart!
it also makes some other important points: even assuming any of these worlds had air we could breathe, they're probably not very habitable. most of them are much larger than earth, which tends to suggest much higher surface gravity. they're also -- again, making the assumption of air we can breathe -- either too hot or too cold for us.
more subtly, the light on many of these worlds is very dim to our eyes. the green band indicating the handwaved habitable zone goes a lot further out for the cooler stars. that's because more of their light is in the infrared. that's great for keeping the planet warm, but not so much for seeing by. that's good to know, but the PR folks at NASA don't like to play that up. it gets in the way of telling a good story.
1: loosely, the habitable zone™ is defined where water could be liquid -- anywhere from just below boiling to just above freezing -- making some hefty assumptions about the conditions on the planet. notably, we have to assume an atmosphere (reasonable, given these planets' likely masses), assume an atmospheric composition (entirely unknown), assume a surface albedo (reflectivity, also entirely unknown) and ignore a bunch of ugly feedback effects among the assumptions. notably, it's easy to find combinations that lead to run-away greenhouse effects, like venus has, or run-away freezing, leading to "snowball" planets in perpetual ice ages.
but if you ignore all that, it's great science. :)
2: the next generation of orbital telescopes will start to be able to look for atmospheres around exo-planets. some of them will be able to tell us about the atmospheric compositions. but you'll need to wait a few years for the earliest of those results.
usually, these announcements are accompanied by pretty pictures showing earthlike planets with atmospheres, seas, and clouds. unfortunately for science, we don't actually know any of that². all we know about these planets is an estimate of their orbital period, which gives us an estimate of their distances from their stars, and a guess about how big they are. that's it. no air, much less seas and clouds and other features indicating people will eventually be able to start new lives in the off-world colonies.
so i'm insanely pleased that NASA is running a scientifically accurate picture of what we know:
and it's a very information-dense image too: not only does it show the planets' orbits and sizes, it provides comparisons of those to venus, earth, and mars; it tells us about the color of the stars they orbit; and even whether what we're looking at was just reported or old news. be still, my geeky heart!
it also makes some other important points: even assuming any of these worlds had air we could breathe, they're probably not very habitable. most of them are much larger than earth, which tends to suggest much higher surface gravity. they're also -- again, making the assumption of air we can breathe -- either too hot or too cold for us.
more subtly, the light on many of these worlds is very dim to our eyes. the green band indicating the handwaved habitable zone goes a lot further out for the cooler stars. that's because more of their light is in the infrared. that's great for keeping the planet warm, but not so much for seeing by. that's good to know, but the PR folks at NASA don't like to play that up. it gets in the way of telling a good story.
1: loosely, the habitable zone™ is defined where water could be liquid -- anywhere from just below boiling to just above freezing -- making some hefty assumptions about the conditions on the planet. notably, we have to assume an atmosphere (reasonable, given these planets' likely masses), assume an atmospheric composition (entirely unknown), assume a surface albedo (reflectivity, also entirely unknown) and ignore a bunch of ugly feedback effects among the assumptions. notably, it's easy to find combinations that lead to run-away greenhouse effects, like venus has, or run-away freezing, leading to "snowball" planets in perpetual ice ages.
but if you ignore all that, it's great science. :)
2: the next generation of orbital telescopes will start to be able to look for atmospheres around exo-planets. some of them will be able to tell us about the atmospheric compositions. but you'll need to wait a few years for the earliest of those results.