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“...at least a quarter of the stars in the Milky Way galaxy have a planet like Earth, with surface conditions that are very similar to Earth, and the chemistry

by rotexo 8y ago

“...at least a quarter of the stars in the Milky Way galaxy have a planet like Earth, with surface conditions that are very similar to Earth, and the chemistry of life as we know it could develop.” I was rather surprised by this claim. Isn’t it currently beyond our ability to detect earth-sized planets around other stars? Isn’t it also beyond our capability to directly detect surface conditions on planets around other stars?

nateberkopec 8y ago
It is not beyond our ability, as "detecting earth-sized planets" was the explicit mission of the Kepler spacecraft.
- rotexo 8y ago
  I guess I should ask a different question then. Have we detected any earth-sized planets? I can only remember hearing about super-earths and gas giants, and I generally read the exoplanet discovery announcements when I see them.
  - skykooler 8y ago
    We have indeed. This page has some that are also in the habitable zone: https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets https://en.wikipedia.org/wiki/List_of_potentially_habitable_... Note that, while some are super-earths, others like Kepler-438b or the planets in the TRAPPIST-1 system are Earth-sized or smaller.
anoncoward111 8y ago
This is actually a really weird claim. We know now thanks to Kepler that many stars have planets just like our Sun does, but so far we've only been able to see large gaseous planets and a few rocky ones that can be as large as 1.5x Earth. 25% sounds way too high. We have not even found many stars like our own with rocky Earths like our own yet. I am certain we will eventually find them, but I think the number of rocky planets with oxygen atmosphere and liquid water is going to be under 1%. Life is most likely rare but abundant- 1% of 100 billion is a butt-ton of Earths
tokai 8y ago
You should be able to look up the exact numbers here[0]. Figure 1 in this paper[1] shows a radii histogram of kepler sub gas giant exoplanet candidates. [0] https://exoplanetarchive.ipac.caltech.edu/ https://exoplanetarchive.ipac.caltech.edu/ [1] https://arxiv.org/pdf/1806.05909.pdf https://arxiv.org/pdf/1806.05909.pdf
flukus 8y ago
Possibly an extrapolation from Kepler data, which can only see planets orbiting at the right angle. If it were to be looking at an extra-solar system "top down" then it wouldn't find any planets. For astronomers "earth like" is just about anything within an order of magnitude of earths size and within the very vague habitable zone, it doesn't say anything about it's surface conditions.

by rotexo 8y ago

nateberkopec 8y ago

It is not beyond our ability, as "detecting earth-sized planets" was the explicit mission of the Kepler spacecraft.

rotexo 8y ago
I guess I should ask a different question then. Have we detected any earth-sized planets? I can only remember hearing about super-earths and gas giants, and I generally read the exoplanet discovery announcements when I see them.
- skykooler 8y ago
  We have indeed. This page has some that are also in the habitable zone: https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets https://en.wikipedia.org/wiki/List_of_potentially_habitable_... Note that, while some are super-earths, others like Kepler-438b or the planets in the TRAPPIST-1 system are Earth-sized or smaller.

anoncoward111 8y ago

This is actually a really weird claim. We know now thanks to Kepler that many stars have planets just like our Sun does, but so far we've only been able to see large gaseous planets and a few rocky ones that can be as large as 1.5x Earth. 25% sounds way too high. We have not even found many stars like our own with rocky Earths like our own yet. I am certain we will eventually find them, but I think the number of rocky planets with oxygen atmosphere and liquid water is going to be under 1%. Life is most likely rare but abundant- 1% of 100 billion is a butt-ton of Earths

tokai 8y ago

You should be able to look up the exact numbers here[0]. Figure 1 in this paper[1] shows a radii histogram of kepler sub gas giant exoplanet candidates. [0] https://exoplanetarchive.ipac.caltech.edu/ https://exoplanetarchive.ipac.caltech.edu/ [1] https://arxiv.org/pdf/1806.05909.pdf https://arxiv.org/pdf/1806.05909.pdf

flukus 8y ago

Possibly an extrapolation from Kepler data, which can only see planets orbiting at the right angle. If it were to be looking at an extra-solar system "top down" then it wouldn't find any planets. For astronomers "earth like" is just about anything within an order of magnitude of earths size and within the very vague habitable zone, it doesn't say anything about it's surface conditions.