Exoplanet may reveal secrets about the edge of habitability

Date:
June 21, 2023
Source:
Cornell University
Summary:
How close can a rocky planet be to a star, and still sustain water
and life? A recently discovered exoplanet may be key to solving
that mystery.


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FULL STORY ==========================================================================
How close can a rocky planet be to a star, and still sustain water and
life? A recently discovered exoplanet may be key to solving that mystery.

"Super-Earth" LP 890-9c (also named SPECULOOS-2c) is providing important insights about conditions at the inner edge of a star's habitable zone
and why Earth and Venus developed so differently, according to new
research led by Lisa Kaltenegger, associate professor of astronomy at
Cornell University.

Her team found LP 890-9c, which orbits close to the inner edge of its
solar system's habitable zone, would look vastly different depending on
whether it still had warm oceans, a steam atmosphere, or if it had lost
its water - - assuming it once had oceans like Earth's.

"Looking at this planet will tell us what's happening on this inner edge
of the habitable zone -- how long a rocky planet can maintain habitability
when it starts to get hot," Kaltenegger said. "It will teach us something fundamental about how rocky planets evolve with increasing starlight,
and about what will one day happen to us and Earth." Kaltenegger is
the lead author of "Hot Earth or Young Venus? A Nearby Transiting Rocky
Planet Mystery," published in Monthly Notices of the Royal Astronomical Society: Letters.

LP 890-9c is one of two super-Earths orbiting a red dwarf star located
100 light years from Earth, researchers announced last year. They said
liquid water or an atmosphere rich in water vapor was possible on LP
890-9c, which is about 40% larger than Earth and circles the small,
cool star in 8.5 days.

Those criteria suggested it to be one of the best targets for JWST to
study among the known, potentially habitable terrestrial planets, in
addition to the TRAPPIST-1 system.

The team's models are the first to detail differences in the chemical signatures generated by rocky planets near the habitable zone's interior boundary, based on variables including the planet's size, mass, chemical makeup, surface temperature and pressure, atmospheric height and cloud
cover.

The calculations were key to estimating how much time JWST would need
to confirm the basic composition of an atmosphere -- if there is one.

The models span several scenarios thought to reflect stages of rocky
planets' evolution, ranging from a "hot Earth" where life might still be possible, to a desolate Venus featuring a carbon dioxide atmosphere. In
between are phases Earth is expected to experience as the sun grows
brighter and hotter with age, causing the oceans to gradually evaporate
and fill the atmosphere with steam before boiling off entirely.

How long those processes might take is unknown, and the astronomers say
LP 890- 9c provides a rare opportunity to explore that evolution.

"This planet is the first target where we can test these different
scenarios," Kaltenegger said. "If it's still a hotter Earth -- hot,
but with liquid water and conditions for life -- then the timeline is
slower than we thought. If we see that it's already a full-blown Venus,
then the water gets lost fast." It's possible that LP 890-9c has no
atmosphere and hosts no life, or that it resembles a Venus with thick
clouds that would block light from reflecting and thus yield little information. Deeper investigation promises to provide valuable clues, Kaltenegger said.

"We don't know what this planet on the edge of habitability could be like,
so we have to look," she said. "This is what real exploration is about."
* RELATED_TOPICS
o Space_&_Time
# Extrasolar_Planets # Venus # Kuiper_Belt #
Astronomy # Pluto # Solar_System # Stars #
Asteroids,_Comets_and_Meteors
* RELATED_TERMS
o Extrasolar_planet o Uranus o Extraterrestrial_life o
Venus o Saturn o Gas_giant o Planetary_habitability o
Eris_(dwarf_planet)

========================================================================== Story Source: Materials provided by Cornell_University. Original written
by James Dean, courtesy of the Cornell Chronicle. Note: Content may be
edited for style and length.


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Link to news story: https://www.sciencedaily.com/releases/2023/06/230621105434.htm

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