Sky & Telescope - January 2022 - 10

S. BIALY ET AL. / ASTROPHYSICAL JOURNAL LETTERS 2021
NEWS NOTES
STARS
Supernovae Hollowed Out " Giant Cavity "
MILLIONS OF YEARS AGO, supernova
blasts cleared a giant hollow in space,
triggering the next generation of stars
in their wake.
Shmuel Bialy (Center for Astrophysics,
Harvard & Smithsonian), Reimar
Leike (Max Planck Institute for Astrophysics,
Germany), and colleagues
pieced together this remarkable story
based on dust.
Last year, Leike created an unprecedentedly
sharp map of cosmic dust
in the solar neighborhood using the
distances to stars measured by the European
Space Agency's Gaia satellite. By
comparing stars' measured brightness
with how bright they ought to be, given
their spectral class, Leike could estimate
the amount of dust dimming the light.
Now, Bialy and colleagues have used
the dust map to disentangle two nearby
star factories, the Perseus and Taurus
molecular clouds. They publish the
results in the September 20th Astrophysical
Journal Letters.
SOLAR SYSTEM
Amateurs Spot Impact Flash at Jupiter
AMATEUR ASTRONOMER José Luis
Pereira of Brazil discovered a probable
impact at Jupiter on September 13th at
around 22:39:30 UT (18:39:30 EDT).
Weather conditions were poor at the
time, but Pereira decided to search
for possible flashes anyway using the
DeTeCt software (see page 52). The program
alerted him that there was a high
probability that he'd caught a collision.
He immediately sent a message to Marc
Delcroix, who helped create the software,
for confirmation. Several other
observers independently saw or recorded
the flash.
This is the 10th recorded impact at
Jupiter, starting with the first one in
July 1994, when fragments of sundered
Comet Shoemaker-Levy 9 slammed into
the planet and left a trail of prominent,
dark impact scars.
Initial rough estimates put the new
Impact
impactor's size at 100 meters (328 feet),
but there were no reports of dark impact
scars following the flash.
¢BOB KING
See more reports and images at
https://is.gd/Jupiterimpact2021.
This frame shows the moment of impact that
German amateur astronomer Harald Paleske
captured via recorded video.
10 JANUARY 2022 * SKY & TELESCOPE
IN BRIEF
Probe Passes Mercury
On October 1st, BepiColombo finally
reached Mercury - and shot right past
it. The joint mission of the European
Space Agency (ESA) and Japan Aerospace
Exploration Agency (JAXA) will
ultimately whizz by the innermost planet
five more times before finally entering
orbit in December 2025. During this first
encounter, BepiColombo approached the
planet's nightside and viewed a gibbous
Mercury on the outbound path. At its
closest, the spacecraft's trajectory brought
it within 200 kilometers (120 miles) of
the surface. BepiColombo is a stack of
three spacecraft: ESA's Mercury Planetary
Orbiter, JAXA's Mercury Magnetospheric
Orbiter (named " Mio " ), and ESA's Mercury
Transfer Module that propels them. Many
of the MPO's instruments were facing Mio
to protect against damage during the long
cruise, so they can't see space at all right
now. But all of Mio's fields-and-particles
instruments were operating during the
flyby and studying the planet's magnetoAstronomers
have long suspected an
association between the Perseus and
Taurus clouds. Using tools that visualize
the 3D dust distribution, Bialy's team
showed that the clouds are actually on
opposite sides of a giant, empty cavity
- a supernova-blown superbubble
500 light-years across. Other data,
including the emission of X-rays and an
abundance of the aluminum-26 isotope,
both coming from hot gas inside the
shell, support the supernova scenario.
" I think that the [researchers] make
a very convincing case for a cavity powered
by a few supernova explosions, "
says Evangelia Ntormousi (Normal
School of Pisa, Italy), who was not
involved in the study.
The superbubble would have taken
at least 6 million years to grow so large.
However, if it were older than 22 million
years, then the bubble would have
dissipated into the interstellar medium.
In other words, at some point after the
existence of early apes but well before
Perseus
PerseusTaurus
shell
y
x
Sun
Taurus
z
pThe Perseus and Taurus star-forming clouds
lie on opposite sides of a large cavity.
the first humans evolved, a series of
supernovae lit up this area of the sky,
and now we can see the long-term consequences
of those blasts. As supernovapowered
shock waves swept through the
region, they compressed dust and gas
into what are now star-forming clouds
lining the cavity's edge. These new data
provide the first 3D view of the longheld
idea that the deaths of stars can
trigger new generations.
¢MONICA YOUNG
Interactive map at https://is.gd/PerTau
https://www.is.gd/PerTau https://www.is.gd/Jupiterimpact2021
Sky & Telescope - January 2022

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