New research explores how super flares affect planets’ habitability
From: University of North Carolina at
Chapel Hill
Ultraviolet light from giant stellar
flares can destroy a planet’s habitability. New research from the University of North Carolina at Chapel Hill will
help astrobiologists understand how much radiation planets experience during
super flares and whether life could exist on worlds beyond our solar system.
Super flares are bursts of energy that
are 10 to 1,000 times larger than the biggest flares from the Earth’s sun.
These flares can bathe a planet in an amount of ultraviolet light huge enough
to doom the chances of life surviving there.
Researchers from UNC-Chapel Hill have
for the first time measured the temperature of a large sample of super flares
from stars, and the flares’ likely ultraviolet emissions. Their findings,
published Oct. 5 ahead of print in Astrophysical Journal, will allow
researchers to put limits on the habitability of planets that are targets of
upcoming planet-finding missions.
“We found planets orbiting young stars
may experience life-prohibiting levels of UV radiation, although some
micro-organisms might survive,” said lead study author Ward S. Howard, a
doctoral student in the Department of Physics and Astronomy at UNC-Chapel Hill.
Howard and colleagues at UNC-Chapel Hill
used the UNC-Chapel Hill Evryscope telescope array and NASA’s Transiting
Exoplanet Survey Satellite (TESS) to simultaneously observe the largest sample
of super flares.
The team’s research expands upon
previous work that has largely focused on flare temperatures and radiation from
only a handful of super flares from a few stars. In expanding the research, the
team discovered a statistical relationship between the size of a super flare
and its temperature. The temperature predicts the amount of radiation that
potentially precludes on-surface life.
Super flares typically emit most of
their UV radiation during a rapid peak lasting only five to 15 minutes. The
simultaneous Evryscope and TESS observations were obtained at two-minute
intervals, ensuring multiple measurements were taken during the peak of each
super flare.
This is the first time the temperatures
of such a large sample of super flares has ever been studied. The frequency of
observations allowed the team to discover the amount of time super flares can
cook orbiting planets with intense UV radiation.
The flares observed have already
informed the TESS Extended Mission to discover thousands of exoplanets in orbit
around the brightest dwarf stars in the sky. TESS is now targeting high
priority flare stars from the UNC-Chapel Hill sample for more frequent
observations.
“Longer term these results may inform
the choice of planetary systems to be observed by NASA’s James Webb Space
Telescope based on the system’s flaring activity,” said study co-author
Nicholas M. Law, associate professor of physics and astronomy at UNC-Chapel
Hill and principal investigator of the Evryscope telescope.
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