Credit: NASA/JPL-Caltech—Cropped from: PIA22093: TRAPPIST-1 Planet Lineup—Updated Feb. 2018, Public Domain, https://commons.wikimedia.org/w/index.php?curid=76364487
We tend to think of habitability in terms of individual planets and their potential to host life. But barring outliers like rogue planets with internal heating or icy moons with subsurface oceans created by tidal heating, it's exoplanet/star relationships that generate habitability, not individual planets. New research emphasizes that fact.
Red dwarfs are known for their powerful stellar flaring, which could render nearby planets uninhabitable. However, even relatively quiescent stars like our sun create space weather. Solar flares, stellar wind, and coronal mass ejections have different effects on different types of planets. Earth is largely protected from these effects by its magnetosphere.
However, over long periods, space weather can have powerful effects on how an exoplanet's atmosphere develops. New research to be published by the American Astronomical Society outlines these effects on the climates of tidally locked exoplanets. It's titled "Effects of transient stellar emissions on planetary climates of tidally-locked exo-Earths," and the lead author is Howard Chen from the Department of Aerospace, Physics, and Space Sciences at the Florida Institute of Technology. It is currently available on the arXiv preprint server.
"Space weather events in planetary environments sourced from transient host star emissions, including stellar flares, coronal mass ejections, and stellar proton events, can substantially influence an exoplanet's climate and atmospheric evolution history," the authors write. "These time-dependent events may also affect our ability to measure and interpret its properties by modulating reservoirs of key chemical compounds and changing the atmosphere's brightness temperature."
The photochemistry of exoplanet atmospheres is a well-researched topic, but this work stands apart from most previous research. It utilizes 3D general circulation models, while most prior work relies on single-column models. Single-column models focus on verticality and how moisture, energy, and momentum in columns affect an atmosphere in a single location. 3D models do a better job of simulating an entire atmosphere and include both vertical and horizontal effects. They incorporate large-scale effects like jet streams that single-column models don't.
This work focuses on stellar flares and the energetic particles they shower exoplanets with. The authors explain, "We examine their effects on synchronously rotating TRAPPIST-1e-like planets on a range of spatiotemporal scales." TRAPPIST-1e is a well-known and often studied rocky exoplanet in the habitable zone of TRAPPIST-1, an ultracool red dwarf star.
We tend to think of habitability in terms of individual planets and their potential to host life. But barring outliers like rogue planets with internal heating or icy moons with subsurface oceans created by tidal heating, it's exoplanet/star relationships that generate habitability, not individual planets. New research emphasizes that fact.
Red dwarfs are known for their powerful stellar flaring, which could render nearby planets uninhabitable. However, even relatively quiescent stars like our sun create space weather. Solar flares, stellar wind, and coronal mass ejections have different effects on different types of planets. Earth is largely protected from these effects by its magnetosphere.
However, over long periods, space weather can have powerful effects on how an exoplanet's atmosphere develops. New research to be published by the American Astronomical Society outlines these effects on the climates of tidally locked exoplanets. It's titled "Effects of transient stellar emissions on planetary climates of tidally-locked exo-Earths," and the lead author is Howard Chen from the Department of Aerospace, Physics, and Space Sciences at the Florida Institute of Technology. It is currently available on the arXiv preprint server.
"Space weather events in planetary environments sourced from transient host star emissions, including stellar flares, coronal mass ejections, and stellar proton events, can substantially influence an exoplanet's climate and atmospheric evolution history," the authors write. "These time-dependent events may also affect our ability to measure and interpret its properties by modulating reservoirs of key chemical compounds and changing the atmosphere's brightness temperature."
The photochemistry of exoplanet atmospheres is a well-researched topic, but this work stands apart from most previous research. It utilizes 3D general circulation models, while most prior work relies on single-column models. Single-column models focus on verticality and how moisture, energy, and momentum in columns affect an atmosphere in a single location. 3D models do a better job of simulating an entire atmosphere and include both vertical and horizontal effects. They incorporate large-scale effects like jet streams that single-column models don't.
This work focuses on stellar flares and the energetic particles they shower exoplanets with. The authors explain, "We examine their effects on synchronously rotating TRAPPIST-1e-like planets on a range of spatiotemporal scales." TRAPPIST-1e is a well-known and often studied rocky exoplanet in the habitable zone of TRAPPIST-1, an ultracool red dwarf star.
TRAPPIST-1 is a well-known and often-studied red dwarf star that hosts multiple rocky exoplanets, three of which are in the potentially habitable zone.
Credit: NASA
Data from NASA's Kepler mission shows that stellar flare energy and amplitude don't vary much between F, G, and K-type stars. However, the frequency of flaring events and their spectral distribution vary a lot depending on the type of star. Flares with the same energy can have different spectral distributions, meaning that some can emit relatively harmless optical light while others can emit X-rays and UV. Spectral distribution is related to underlying processes in the star, like activity in the magnetosphere and chromosphere.
Stars like TRAPPIST-1 are known to have high levels of magnetosphere and chromosphere for billions of years, which can generate superflares. "This can affect atmospheric environments of close-in exoplanets on long timescales, inducing water loss via photolysis and hydrogen escape," the authors write.
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