Page 15 - Astronomy - October 2017 USA

ASTRONEWS FLARE-UPS. A new catalog based on data from the Galaxy Evolution Explorer spacecraft will allow astronomers
to determine how stellar flares from cool dwarf stars could affect the habitability of their planets.

TRAPPIST-1’s planets

may trade life

The TRAPPIST-1 planetary system could be one of the
most promising places to find life — if its star isn’t too
volatile. A paper by Manasvi Lingam and Abraham
Loeb, published June 14 in the Proceedings of the
National Academy of Sciences, suggests that if the sys-
tem is habitable, its planets might more or less share
the same life.
The TRAPPIST-1 system was initially announced in
May 2016 as a three-planet system around a star
slightly larger than Jupiter. At the time, astronomers
believed two of its planets were habitable. Further
study revealed that the third, erratic planet was actu-
ally several planets, bringing the total number of plan-
ets (so far) to seven.
The planets are tightly packed, with distances
between them similar to the separation of Earth and
the Moon. Each orbits in resonance with the others. But
these close distances could have a strange effect: It
wouldn’t be hard for meteorites to hop from one
planet to another, bringing life along with them.
The likely “passengers” would be microbial. The
paper suggests this hypothesis could be proven if the
same biosignatures are found on multiple planets,
something that might be possible by comparing the
planets’ atmospheres using the upcoming James Webb
Space Telescope.
Like many small M-dwarf stars, TRAPPIST-1 is fairly
active, shooting out flares that could strip its planets of
their atmospheres. A recently discovered planet CLOSE NEIGHBORS. The TRAPPIST-1 system, seen here in an artist’s depiction, is packed so tightly
around an M dwarf appears to have retained its atmo- that the planets orbit in resonance with less than a million miles between neighbors. If the star hasn’t
sphere, however, meaning it is possible that these fried away the planets’ atmospheres, the system could be a promising place to find alien life. NASA/
planets could cling to their gas layers. — J. W. JPL-CALTECH

Amateur sleuths

find a new nearby

brown dwarf

NASA/CXC/RUTGERS/J. WARREN AND J. HUGHES ET AL. covered a brown dwarf just over 100 light-
Citizen scientists using Zooniverse’s
Backyard Worlds: Planet 9 tool have dis-
years from Earth, increasing the number of
objects in our Sun’s neighborhood.
The project, which launched in
February, almost immediately began yield-
ing results. For instance, the dim brown
dwarf pictured was found just six days into
Fletcher is credited with the initial discov-
dim brown dwarf through the Backyard Worlds:
ery, and three other teams identified it
Planet 9 project. It had eluded detection by
Tycho in 3-D the effort. Australian schoolteacher Bob NEW FIND. Citizen scientists discovered this
around the same time.
surveys looking for brighter objects. NASA
Brown dwarfs, often called “failed
stars,” are more massive than planets but Worlds: Planet 9 was designed with a hard-
WHAT’S IN A SHAPE? Researchers built this 3-D image less massive than stars, so they are unable to-find target in mind: Planet Nine, a possi-
of the Tycho supernova remnant to better understand the
expansion of the violent stellar event. The NASA-led team to fuse hydrogen into helium. While some ble cold ice giant about the size of
sought to understand asymmetries in supernova remnants brown dwarfs can be quite warm because Neptune at the margins of our solar sys-
to determine if their shape develops during or after the they fuse deuterium (a relatively scarce tem. Because of the search parameters
supernova. The model used 12 years’ worth of data from isotope of hydrogen), WISEA required to find such an object, the
the Chandra X-ray Observatory to determine that various J110125.95+540052.8 — some just call it Backyard Worlds project is also primed to
“knots” are moving at different velocities. They concluded “Bob’s dwarf” — is comparatively cold, just discover other nearby cold objects, includ-
the explosion was likely symmetric; the asymmetries a few degrees warmer than Jupiter. ing dwarf planets and brown dwarfs.
were caused by interactions with matter in the interstellar The object was too faint to be detected The research was published May 24 in
medium as the shock wave expanded outward. — J. W. by previous sky surveys, but Backyard The Astrophysical Journal Letters. — J. W.
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