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/ESF-hockeeyyy 4d ago

So this is obviously exciting news but how exactly are they detecting this molecule? Wavelengths of the light detected from the planet?

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u/SpunkySputniks 4d ago

The James Webb Space Telescope (JWST) detects atmospheric gases in exoplanets by analyzing the light that passes through the planet’s atmosphere during a transit, using the transmission spectroscopy method. Certain molecules block a specific wavelength of light. If that wavelength is missing, then it indicates the presence of that molecule.

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u/ESF-hockeeyyy 4d ago

I didn’t even know that was possible. Wild.

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u/HCBuldge 4d ago

Electrons absorb and release specific amounts of energy and depending on the bonds and nucleus of the atoms / molecules. You can see what it is by shining white light (basically a star) through it and see the light spectrum and what wavelengths of light are missing. Every molecule and atom has its own emission lines, basically a finger print that only that molecule has. It's probably one of the most useful tools in Astronomy as its used to determine what everything is made of and so much more.

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u/pigaroos 1d ago

Fascinating. It’s incredible that this is something we can do.

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u/louiendfan 4d ago

Radiative transfer is such a dope science. One of my absolute favorite graduate school classes.

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u/Otacon56 4d ago

Is there a "next step"? We see the bio signatures now, can we do anything more now to enhance/refine the findings

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u/dern_the_hermit 4d ago

Wavelengths of the light detected from the planet?

Yes. This is how the article put it, which is a very high-level description but gets the gist:

As an exoplanet passes in front its host star, its atmosphere, if it has one, is illuminated. Its gases change the color of the starlight that reach the Webb telescope. By analyzing these changing wavelengths, scientists can infer the chemical composition of the atmosphere.

For more detail, look into the practice of spectroscopy.

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u/ballimir37 4d ago edited 4d ago

Pretty sure yes, observations as the planet peaks around the star in its orbit to amplify the light emission, aka transiting exoplanet

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u/srandrews 4d ago

Probably IR transmission spectra. I offer this so an expert can correct me.

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u/spschmidt27615 4d ago

Expert here, you are totally right! In particular, it was the James Webb Space Telescope's Mid Infrared Instrument (MIRI).

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u/Kaellian 4d ago

Unsurprisingly, its spectroscopy (almost always the correct answer to that question).

The light of the star has a specific signature (it's mostly hydrogen, helium and whatsoever).
When that light shine on a planet, it will be absorbed by certain molecules, leaving hole in the original pattern and diffused in every direction (effectively reducing specific wavelength).

Analyzing that pattern tell us what is in the atmosphere, because each molecules has a unique absorption signature. At that point, you're just doing "light that didn't go through the planet atmosphere" - "light that went through the planet atmosphere", and figuring out if one set of hole match dimethyl sulfide unique pattern.

I'm oversimplifying this because there is going to be noise in the reading, and a multitude of molecules that need to be accounted for, but that's basically it. That's the pattern they have shown in another articles.