How can we tell if far off exoplanets have oxygen?
I thought it was because they would glow blue but Uranus and Neptune are blue and they don’t have oxygen?
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answers:
Jeffrey K say: Light passing thru an atmosphere with oxygen has specific wavelengths absorbed. Astronomers can use a spectrometer to look for these absorption lines. It is difficult but its possible.
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Jim say: The detection of any substance on a distant planet is a matter of detecting the characteristic EM spectrum of such a substance. To detect such characteristic spectra from exoplanets would require very sensitive instruments. I am not away if any instruments of sufficient sensitivity exists.
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Dances with Weed say: Sceientists van tell by studying the light an object gives off.
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WHANKING-WILLY say: There is many types of Oxygen. Do mean the breathable type? Read above.
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busterwasmycat say: It isn't the big color class that matters, it is the specific wavelengths that declare the existence of a particular element. Every element has its own particular line spectrum, where each line corresponds to an energy difference between possible electron "locations". Electron locations are like shelves on the wall at different heights, and the shelves are at specific and distinct heights for each element, so the difference between one shelf and the next will have a specific change in potential energy that it emits (or absorbs, depending on the situation), and that energy, because E=h*nu, has a very specific wavelength.
So, if you want to know if a particular element is present, it is very useful to look at the size of the signal at a very particular wavelength, one that is only from that element and not close to a similar one from another element (no possibility of overlap). The size of the signal will be proportional to the amount of the element (among other things).
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Robert say: We send a probe there.
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Nyx say: Through the usage of spectroscopy.
https://arxiv.org/pdf/1709.05941.pdf
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CarolOklaNola say: When the planet transits the star and the star light goes through the atmosphere , the oxygen absorbs, reflects and emits s photons AF specific wavelengths and frequencies, so a spectroscope will tell if there is oxygen. So far we can resolve only super Earth's, but as the technology improves we will be able to resolve smaller Earth and Venus sized planets.
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tentofield say: When a planet orbiting a distant star passes in front of that star, the light from the star passes through the atmosphere of the planet. We can see that light and analyse it with a spectrometer. The spectrogram of the light from the star tells us what elements are in the star. As the planet moves in front of the planet, the atmosphere absorbs light depending on the elements in the atmosphere. We can see those elements on a spectrogram. Any elements not on the star's spectrogram must be in the atmosphere of the planet and if one of those is oxygen, we know the planet's atmosphere has oxygen.
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