Sky & Telescope - December 2021 - 10

NEWS NOTES
SOLAR SYSTEM
Venus: Thin-Skinned and
Ready to Blow
A SMALL VOLCANIC FEATURE on the
edge of a Venusian corona gives further
credence to the theory that our sister
planet has a thin outer layer and an
active interior.
Megan Russell and Catherine
Johnson (both at University of British
Columbia, Canada) published an
analysis of the peculiar feature in the
August Journal of Geophysical Research:
Planets. Dubbed Narina Tholus, the
steep-sided volcanic dome perches on
the edge of Aramaiti Corona, as seen
in radar maps from NASA's Magellan
orbiter. Coronae are common on Venus,
thought to be giant volcanic upwellings
that later collapsed in the center. Aramaiti
is likely only 1.4 million years old,
making Narina, which clearly formed
afterwards, even younger.
Russell modeled the heat flow under
the surface using a method that has
at most a third as thick as Earth's.
Paul Byrne (Washington University
in St. Louis), who was not involved in
this study, agrees that the result adds to
growing evidence that Venus is an active
world. " They've used very established
techniques, " Byrne says. " And they've
been able to get results consistent
with volcanic activity that is relatively
geologically recent. This is important
because anything that's relatively recent
is probably ongoing. "
The stereo radar needed to extend
100 kilometers
pA Magellan radar image of Aramaiti Corona
shows Narina Tholus (red, center left).
been used extensively to study volcanic
activity on Earth. Feeding radar images
into a computer simulation, she then
predicted the effects of the dome's
" load " on its surroundings. She was able
to reproduce the shape of Narina Tholus
when the surrounding lithosphere was
this analysis is currently only available
for 20% of the planet's surface. Russell
found 13 other coronae accompanied
by steep-sided domes within those
data, but none of those had the flexing
pattern that she used to measure
the underground heat flow. Future
missions such as NASA's VERITAS and
DAVINCI+, and the ESA's EnVision
(S&T: Oct. 2021, p. 17) offer the hope
of detecting other small features like
Narina Tholus.
¢ARWEN RIMMER
STARS
Red Dwarfs Aren't So Bad
(for Planets) After All
RED DWARF STARS APPEAR to flare
preferentially at high latitudes, a feature
that might keep their exoplanets
habitable instead of hellish. The results
appear in the October Monthly Notices
of the Royal Astronomical Society.
Red dwarf stars make up 75% of the
stars in the Milky Way. Also known as
M dwarfs, they're much cooler than
the Sun, and their churning guts and
fast rotation make them prone to more
extreme magnetic activity. To be potentially
habitable, any planet would have
to orbit a red dwarf closely, but that
proximity would put it in a vulnerable
position. Flares and energetic particles
from the magnetically active star can
strip a planet's atmosphere.
Now, a team lead by Ekaterina Ilin
(Leibniz Institute for Astrophysics Potsdam,
Germany) suggests that the flares
might not be as destructive as once
10 DECEMBER 2021 * SKY & TELESCOPE
thought. Ilin and her colleagues combed
through data from NASA's Transiting
Exoplanet Survey Satellite to find four
red dwarfs exhibiting flares that lasted
longer than the rotation period of the
star. Each star's spin left a rotational
fingerprint on the light curve that
enabled Ilin's team to pinpoint each
flare's location on its star's globe.
The team found that the flares all
occurred near the poles, at latitudes
between 55° to 81°. That's different
from solar flares, which as a general
rule occur within 30° of the equator.
Although the sample size is small,
Cynthia Froning (University of Texas,
Austin), who was not involved in the
study, thinks the results are significant.
There's only a 1 in 1,000 chance that all
the flares would have occurred at high
latitudes if they were equally likely to
happen at any latitude.
If M dwarf flares typically occur at
high latitudes, planets orbiting in the
plane of the star's equator - which is
the case for worlds around such stars
pAn artist's impression shows a flaring red
dwarf and its exoplanet.
where inclinations are known - would
never encounter the outbursts of energetic
particles or intense radiation.
Perhaps the most common stars in
the galaxy could host habitable planets
after all.
¢LAUREN SGRO
Read more at https://is.gd/Mstars.
CORONA MAP: PLANETARY SCIENCE INSTITUTE; RED
DWARF: AIP / J. FOHLMEISTER
https://www.is.gd/Mstars
Sky & Telescope - December 2021

Table of Contents for the Digital Edition of Sky & Telescope - December 2021
