Sky & Telescope - April 2024 - 9

STARS
IN BRIEF
A Brilliant Explosion That Keeps on Exploding
A BLAZING BLUE DOT
appeared in images
taken by the Zwicky
Transient Facility in
2022; the dot shone
some 1,000 times
brighter than a typical
supernova before fading
away. That event,
designated AT2022tsd
and soon nicknamed
the Tasmanian Devil,
joined a short list of other luminous fast
blue optical transients (LFBOTs; S&T:
May 2019, p. 10). Astronomers think
these transient lights mark a special
kind of supernova, or they could instead
come from a feeding neutron star or
black hole.
But 100 days later, as Anna Ho (Cornell
University) and colleagues were
reviewing routine images to monitor
the fading flare, they found a surprise:
another burst almost as bright as the
original and in the same exact position
on the sky.
Scouring for data in the archive and
with new observations, the astronomers
found another outburst - and
then another, and another. These
flashes were red rather than blue, lasted
minutes at most, and shone with the
power of a supernova. Overall, at least
14 flares followed the first one, Ho and
colleagues report in the November 30th
of ancient freeze-thaw cycles.
" The [wedges] most likely formed by
thermal-contraction cracking, " Zhang
says. Water, soil, or mixtures of the two
filled in the cracks to form the wedges
that the team observed. The meters
of layers on top of the polygons were
deposited over the past 1.6 billion years
by long-term weathering, impacts, and
transient floods.
" It's very interesting they can see
something like that with radar, " says
Benton Clark (Space Science Institute).
" There may be a lot more [ice-related
features] around, but we haven't come
An artist's impression
shows a massive star in
the act of exploding.
Nature; it's likely more
were missed.
Ashley Chrimes
(ESA), who wasn't
involved with the
study, calls the discovery
" completely new
(and unexpected). "
Follow-up observations
showed that while the initial, blue
light probably originated in the heat of
the explosion, subsequent flares probably
come not from heat but from speedy
plasma spiraling along strong magnetic
fields. What's more, the follow-on flares
brighten and fade so quickly that the
source they hail from must be correspondingly
small - no more than a few
times the Sun's width.
The nature of the emissions together
with the small size and extreme energies
suggests that the flares originate
in a jet that's escaping at near-light
speeds, Ho's team concludes. The result
supports ideas that LFBOTs involve
neutron stars or black holes, but it still
leaves open a lot of possibilities. With
the Tasmanian Devil still flashing away,
astronomers may soon be able to narrow
down what causes this unique type
of explosion.
¢MONICA YOUNG
on places where [the ice] was exposed. "
Zhurong landed on May 14, 2021, in
Utopia Planitia, a northern plains site
that might once have hosted an ancient
ocean. In its year of operation, the
rover traveled nearly 1.2 kilometers (0.7
mile). Zhang's team found 16 polygon
wedges buried along Zhurong's trek.
Zhang's team concludes that the
absence of buried polygonal terrain
above the 35-meter level marks a " stark
environmental transition " between 2
and 3.5 billion years ago, during the end
of Mars's wet period.
¢JEFF HECHT
Amateurs Discover
Asteroid's Moon
When the asteroid 5457 Queen's eclipsed
a 12.5-magnitude star on Sept. 4th, Jan
Mánek and five other amateur astronomers
stationed from Poland to Switzerland
timed the exact moment the star winked
out. From their data, astronomers derived
the rough size and shape of the asteroid
- and found something else, too. Mánek
captured not only the 1.67-second asteroid
occultation but also another eclipse of
the same star 0.87 seconds later, as if
another object were following close behind
Queen's. No one else saw the second
occultation that night, but on Sept. 20th,
Serge Dramonis from Greece observed
Queen's occultation of another star. He,
too, saw a " double " eclipse - Mánek and
Dramonis had discovered that Queen's has
a moon. Analysis by Christian Weber (International
Occultation Timing Association,
European Section) revealed that the as-yet
unnamed satellite measures 2.8 km (1.7 mi)
in diameter. Queen's itself, which was discovered
in 1980 by Carolyn Shoemaker, is
only about 17.5 km wide, according to the
same analysis. Hundreds of asteroids are
known to have satellites; however, this one
is only the second main-belt asteroid moon
found and confirmed with the occultation
method.
¢JAN HATTENBACH
Computers Trained to Find
Cosmic Treasure
Graduate student Erik Zaborowski (Ohio
State University) and colleagues developed
a machine-learning algorithm to help
search through millions of images taken
by the Dark Energy Camera at the Cerro
Tololo Inter-American Observatory in Chile.
With the model's help, researchers found
562 new candidate galaxies gravitationally
lensed by massive foreground galaxies.
They published the results in the September
1st Astrophysical Journal. The effort is
part of a survey that uses the Dark Energy
Camera, or DECam, to explore the Milky
Way's neighborhood. The DECam Local
Volume Exploration (DELVE) survey has
captured a whopping 520 million cosmic
sources. Zaborowski's team built a fivelayered
convolutional neural network that
sifted out the 50,000 sources most likely to
be gravitationally lensed galaxies. To make
the final selections, though, the scientists
still had to check each one by eye.
¢HANNAH RICHTER
sk yand tele scope .o r g * APRIL 2024
9
BILL SAXTON (NRAO / AUI / NSF)
http://skyandtelescope.org
Sky & Telescope - April 2024

Table of Contents for the Digital Edition of Sky & Telescope - April 2024
