Author | Lightnews

Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

If alien life fluoresces at the same wavelengths we’re familiar with—and if clouds don’t block too much of our view—then with upcoming telescopes like the Habitable Worlds Observatory, it may be challenging, but possible, to find glow-in-the-dark signs of life on small, rocky exoplanets!

Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

In a follow-up paper, the authors also found that biofluorescence could be useful around cooler red dwarf stars that have ultraviolet “flares"—high-energy bursts that life would need to protect itself from.

Paper 1: academic.oup.com/mnras/articl...
Follow-up: academic.oup.com/mnras/articl...

Alien life may also need protection around cooler stars, whose ultraviolet flares can sometimes strike planets. Life around many types of stars could glow in the dark... if it exists for our telescopes to find.

(Artwork of an astronaut peering down at a glowing planet beneath a red star).

Illustration by Wendy Kenigsberg/Matt Fondeur/Cornell University

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Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

O’Malley-James & Kaltenegger found that if a planet around a bluer F-type star was covered in 70% ocean and 30% lifeforms such as strongly biofluorescent coral on Earth, then we could receive roughly 10% more light at the wavelengths that these organisms emit (see table below for more scenarios)

Pictured at the top is a table with differing values for the increased life we'd receive, depending on how much of the planet these lifeforms cover.

If alien life fluoresces at the same wavelengths we're familiar with—and if it covers enough of the planet—then by observing in these wavelengths, it may be possible to see glow-in-the-dark life.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

On alien planets orbiting bluer stars, where more “sunscreen” is needed, biofluorescence might make up a larger fraction of the light we’d receive in our telescopes. CSI researchers O’Malley-James & Kaltenegger examined biofluorescent life on Earth to determine what glowing colors of light we’d see.

Around stars with higher rates of dangerous ultraviolet light, alien life might fluoresce to protect itself, perhaps even more strongly than our best examples on Earth (similar to the ones pictured here—certain coral species).

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Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

You may be wondering—how bright is this “biofluorescence” anyway? Earth is covered in plants, and many of them emit a small amount of fluorescent light. However, this is just a fraction of a percent of all the green light we see reflected. (More info in Sagan’s Galileo study: tinyurl.com/yc2xtr43)

Many plants on Earth glow via biofluorescence, as mapped here—absorbing high-energy light, then "glowing" at a lower energy. However, planets reflect green light much more than they glow from biofluorescence. (The map shows high biofluorescence in forested regions on Earth).

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Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

The Sun’s ultraviolet light can damage our skin over time, leading to harmful mutations. On planets around slightly hotter “F-type” stars, which emit more blue and ultraviolet light than the Sun, it’s even more crucial to protect yourself. Alien life might use biofluorescence as natural “sunscreen!”

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Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

“Biofluorescence” works the same way as glow-in-the-dark stickers or shirts: some organisms on Earth have pigments that absorb high-energy (mostly ultraviolet) light, then slowly re-emit less energetic light, causing a long-lasting glow.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · 3d

Happy Halloween! ✨ 👻 🎃 Jack-o’-lanterns aren’t the only signs of life that glow in the dark. Some organisms on Earth do, too. Would a distant planet full of glow-in-the-dark aliens be detectable to our telescopes? 🔭

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

Someday soon, we may be able to say that out of 70 habitable zone planets, out of 6000 found, out of hundreds of billions that surely exist in the Milky Way… there is one more corner of the universe that knows itself.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

Recent papers from Carl Sagan Institute researchers and exoplanet scientists worldwide (such as studies of TRAPPIST-1 e!) have brought us one step closer to detecting an atmosphere around an Earth-like, potentially habitable world.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

The star will have to treat its planet kindly, lest it strip away the planet’s atmosphere, or heat the planet so intensely it becomes a “lava world.” Even if the planet avoids these extremes and organisms manage to thrive, the world those organisms call home may look quite different from ours.

Around 70 exoplanets with rocky surfaces in the habitable zone (with artist's depiction of TRAPPIST-1 planets, four of which orbit within the broadest zone that may allow for liquid water on their surface)

*** Stats from the NASA Exoplanet Archive and from under-review habitable zone paper from CSI researchers.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

Some of these planets—the more sedate, less extreme ones—have a chance at hosting life. They’ll need to be not too far, not too close, but just the right distance from their host star: in the “Goldilocks” or “habitable” zone where liquid water could exist on a planet's surface.

87 exoplanets discovered through direct imaging (with real image of b Centauri b, which has 10x the mass of Jupiter but appears small with current imaging technology)

*** Stats from the NASA Exoplanet Archive.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

There is a planet that takes 49 minutes to orbit its pulsar, in a pirouette too tight to ever allow for life; there are red-hot planets where gems may fall from clouds of metal and deep blue dots where glass may rain sideways.

1171 exoplanets with masses likely larger than Jupiter (with artist's depiction of Kepler-7 b, a hot Jupiter—named for size rather than visual similarity, as it is far too hot to have many bands of clouds)

*** Stats from the NASA Exoplanet Archive.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

There are exoplanets that see two Suns in their skies, even three Suns; there are “rogue planets,” likely ejected from the disks of young stars, that shoot through an endless night; there is a planet that takes one million years to orbit its star;

552 exoplanets with more than one sun in their skies (with artist's impression of Proxima Centauri b, closest planet to Earth, and in a triple-star system).

*** Stats from the NASA Exoplanet Archive. Note: 552 exoplanets are in multiple-star systems—though some likely orbit very far from their stars, so the “suns” in their skies wouldn’t be very large!

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 21

6000 exoplanets. 🔭

We’ve found worlds orbiting all sorts of stars, from tiny, slow-burning reds to fast-living blue-whites to middle-of-the-road, prime-of-their-life yellows like our own...

600 exoplanets. The strange worlds we've found so far—and what we still don't know.

***Artist's depiction by Pablo Carlo Budassi (Celestialobjects)

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 14

Just over five hours until Cornell's Alpha CubeSat launches on its way to the International Space Station! Learn more about the satellite, its lightsail, and its holograms at alphacubesat.cornell.edu, and tune into the livestream of the rocket launch there!

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

Congratulations to project lead/CSI engineer Josh Umanksy-Castro, project advisor/CSI fellow Mason Peck, and to all the Cornell students who poured their heart into this mission!

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

The NG-23 ISS commercial resupply mission launch is scheduled for Sunday 9/14 at 6:11pm EST with a backup opportunity on Monday 9/15 at 5:49pm. Alpha will ride to the International Space Station, then patiently wait for its turn to launch off the station and into space in mid-November.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

A large group of Cornell students, alumni, family and friends are traveling to Cape Canaveral this weekend to view the launch! We invite you to join us by tuning into the livestream, linked at alphacubesat.cornell.edu.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

After 9 years and over 100 students, Cornell's Alpha CubeSat mission is launching to space TOMORROW! This small cube-shaped satellite will test the deployment of the first-ever free-flying light sail in low Earth orbit, a stepping stone towards laser sailing to the stars. 🔭

alphacubesat.cornell.edu

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

For now, CSI researchers will construct better and better models for TRAPPIST-1 e's busy host star, until the day we can fully disentangle little planets from jumpy starlight!

Read more: carlsaganinstitute.cornell.edu/news/there-w...
(Papers also linked in article)!

From NASA / Joseph Olmsted: "The Earth-size exoplanet TRAPPIST-1 e, depicted at the lower right, is silhouetted as it passes in front of its flaring host star in this artist’s concept of the TRAPPIST-1 system."

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

But even noisy data lets us rule out a few possibilities—models that would cause much larger dips than the ones in the graph. TRAPPIST-1 e is unlikely to have a huge hydrogen atmosphere, nor a huge carbon dioxide atmosphere like Venus, which traps enough heat to melt lead.

From the second of the two research papers (linked at end of thread): nitrogen-rich (like Earth) atmospheric models, and possible signatures of gases like CH4 (methane).

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

TRAPPIST-1 e orbits a small red dwarf star, which tend to have a lot more stellar activity than our own Sun. The activity of the star might be interfering with what we see.

Graph of host star size and light different planets receive. TRAPPIST-1 e orbits a tiny, very active red dwarf star, and receives less light than Earth.

Artist's impression of a planet and its moon orbiting an active red dwarf star.

Credit: David A. Aguilar / NASA

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

As is typical for tiny planets, noise makes our measurements uncertain, so the white error bars overlap with two models: a possibly Earth-like atmosphere in blue and a bare, airless world in orange. CSI researchers Nikole Lewis, Elijah Mullens, and Ryan Challener say it could go either way.

TRAPPIST-1 e: bare rock or cloudy world? The data on the graph could conceivably fit an "airless" scenario or an "Earth-like atmosphere" scenario.

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Carl Sagan Institute @carlsaganinstitute.bsky.social · Sep 13

What do you see in the light from planet TRAPPIST-1 e?

Signs of alien life? Not yet...

Take a look for yourself at real data in the James Webb Space Telescope graph, and read more about it below! 🔭

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