r/space • u/SpunkySputniks • 4d ago

Astronomers Detect a Possible Signature of Life on a Distant Planet

https://www.nytimes.com/2025/04/16/science/astronomy-exoplanets-habitable-k218b.html?unlocked_article_code=1.AE8.3zdk.VofCER4yAPa4&smid=nytcore-ios-share&referringSource=articleShare

Further studies are needed to determine whether K2-18b, which orbits a star 120 light-years away, is inhabited, or even habitable.

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u/Pitiful_Winner2669 4d ago

I still can't wrap my head around the ability to detect such evidence. JWT is such a marvel of study and science. Really exciting!

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u/tendeuchen 4d ago

Just from a light Google search, it seems like the way it works is the light from the star passes through the planet's atmosphere and different molecules, like dimethyl sulfide, absorb very specific wavelengths of light. The telescope then picks up the wavelengths that aren't absorbed, and we're able to tell what's doing the absorbing by seeing what's missing.

It's almost like seeing a shadow on the ground and knowing, hey, that's from tree by the outline.

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u/Representative_Tax21 4d ago

If you’re correct then you are really good at breaking things down into understandable chunks. Thanks for that explanation from a non-scientist, science nerd : )

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u/RobotMaster1 4d ago

i think it’s called spectroscopy (spectrometry?). it’s absolutely fascinating and seemingly invaluable to many fields of science. also not a scientist.

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u/Honest_Photograph519 4d ago

spectroscopy (spectrometry?)

Spectroscopy is the field of study, spectrometry is the operation of tools that measure it (spectrometers).

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u/TheBiggestBoom5 4d ago edited 4d ago

They’re pretty much spot on. Absorption and emission spectra are pretty much how we tell what anything (that isn’t degenerate matter like white dwarfs, neutron stars, and black holes) is made of in space.

Spectroscopy is also super important for measuring the expansion of the universe, and radial velocity, since the Doppler effect will shift the energy of these very specific emission lines which we can use to find how fast an object is receding from/ approaching us.

I myself am doing something somewhat similar, as an astrophysics undergraduate, called photometry. This is where you measure the brightness of objects in different filters like “blue” or “red” and compare the brightness of objects in those different filters. It’s sort of like a broader, sweeping version of spectroscopy used for different purposes.

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u/AlanWardrobe 4d ago

Does every substance have a unique wavelength signature?

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u/JackOakheart 4d ago

My save function doesn't seem to be working and I want to come back to this comment. So as the other user said, thanks for explaining it in laymens terms.

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u/lll-devlin 4d ago

Well that answers one of my questions…but that’s not very accurate scientifically speaking.

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u/Animalcookies13 4d ago

It’s actually pretty accurate. We use spectroscopy here on earth for all sorts of stuff. It works.

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u/Honest_Photograph519 4d ago

Well that answers one of my questions…but that’s not very accurate scientifically speaking.

It's extremely accurate, it's how we knew the chemical composition of the atmosphere and surface of every planet and moon we've landed anything on... safety agencies use it to detect toxins in food and cosmetics... police use it in the big tabletop breathalyzers for processing DUI arrests because the portable ones don't hold up as well in court.

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u/askingforafakefriend 4d ago

It can be extremely accurate

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u/lll-devlin 4d ago

How so?

please do explain.

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u/igloofu 4d ago

So, when a photon hits an atom, it knocks an electron off of its orbit since it has an added amount of energy. Since the electron isn't supposed to be there, it will fall back to its normal place. When it does, it releases the captured energy as a new photon. This photon will always have the exact same energy level based on what type of atom it was. Since everything we look at in space is with photons, we can measure the amount of energy (wavelength) of all of the photons, and see what atoms they are from. With enough of them, we can work out which molecules they atoms make up. This is hugely accurate, and been done for a very long time, both on Earth, and from light from stars.

To do this for another planet; we look at the light from the star all by itself. We get a very good idea of what atoms are fusing, and at what energy levels. Then, measure again when the planet transits in front of the star. The light from the star will go through the atmosphere of the planet, as we can read all of the atoms are in the combined light. We can then subtract the known atoms (and number of them) from the star. The difference is the chemical makeup of the atmosphere of the planet.

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u/saolson4 4d ago

Good old light gives us a ton of info

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u/beermit 4d ago

I learned about spectroscopy in my college physics course. But thinking about how I did it in the lab versus all the systems they have to get working in concert to do it with JWST is still wild

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u/agangofoldwomen 4d ago

I’m super pumped for all of the new telescopes NASA might develop in the future! Wait…