Sky & Telescope - April 2023 QR - 10

NASA / CORY HUSTON
NEWS NOTES
STARS
Gamma-ray Burst Surprise
GAMMA-RAY BURSTS ARE thought
to come in one of two flavors - those
that last two seconds or less come from
neutron star mergers while longer ones
herald the supernovae of massive stars.
But GRB 211211A, a minute-long blast
of gamma-rays that came from more
than 1 billion light-years away, blurs
that distinction.
The Fermi Gamma-ray Space Telescope
caught this burst on December
11, 2021, recording a strong pulse of
radiation that lasted 13 seconds, followed
by a weaker echo 55 seconds long.
But calling GRB 211211A " long " is akin
to calling a tomato a fruit - while its
gamma-ray emission is indeed longer
than two seconds, it appears to have a
different origin than other long GRBs.
MISSION UPDATE
The Status of Artemis 1
CubeSats
THE HISTORIC ARTEMIS 1 mission
(S&T: Mar. 2023, p. 8) carried with it
10 much smaller payloads to lunar orbit
and beyond. As secondary payloads,
such CubeSats are notoriously difficult
to field - some 50% of those launched
never complete their missions. But
the ones aboard Artemis 1 have fared
slightly better: As of press time, six of
the 10 CubeSats are (or are on track to
be) successful.
ArgoMoon: This joint NASA and
Italian Space Agency (ISA) demonstrator
successfully photographed the
interim stage that placed the rocket on
a Moonbound trajectory. It also sent
back images of Earth and the Moon.
BioSentinel: This NASA mission
carries budding yeast on an 18-month
mission to study the effects of radiation
on life. Although the satellite began to
tumble shortly after deployment, the
team was able to reestablish control.
EQUULEUS: The Japan Aerospace
Exploration Agency (JAXA) built the
Equilibrium Lunar-Earth Point spacecraft
to observe lunar impact flashes
10 APRIL 2023 * SKY & TELESCOPE
pTen CubeSats are nestled in the ring-shaped
stage adapter, which later connected the Orion
capsule to the SLS rocket.
and study Earth's inner magnetosphere.
JAXA has reported that the steam-powered
spacecraft has successfully completed
its lunar flyby and is now headed
to its destination at the L2 Lagrange
point beyond the Moon.
LunaH-Map: The Lunar Polar
Hydrogen Mapper will look for water
ice in the permanently shadowed polar
regions of the Moon. The spacecraft is
healthy and has already collected data
on the lunar surface, but the team is
struggling with propulsion problems.
Lunar IceCube: Also on the hunt
for lunar water ice, this mission made
contact following deployment, but no
further updates have been issued.
Team Miles: Built to demonstrate a
hybrid thruster system and deep space
Eleonora Troja (University of Rome)
and Jillian Rastinejad (Northwestern
University) led follow-up observations,
reported in two separate articles in the
December 8th Nature, showing more
visible-light and infrared emission
than expected relative to the gamma
rays and X-rays. The longer-wavelength
emission was bright enough to indicate
a kilonova, the explosion that follows
a stellar merger. A team led by Alessio
Mei (Gran Sasso Science Institute, Italy)
also reported in Nature that the GRB's
long-lasting high-energy radiation supports
the kilonova scenario.
" Just as a supernova links long
gamma-ray bursts to the collapse of
massive stars, a kilonova is the smoking
gun for a compact binary merger, "
writes Luigi Piro (National Institute for
Astrophysics, Italy) in an accompanying
perspective article.
However, the length of the burst
is hard to explain in this scenario.
Gamma rays from stellar mergers
are thought to come from the disk of
material that temporarily surrounds
and feeds the merged star, and colliding
neutron stars make a disk too small
to power more than a second or two of
gamma rays. Jun Yang (Nanjing University,
China) and colleagues therefore
propose in the same issue of Nature
that a " hybrid " collision between a
neutron star and a white dwarf created
an extremely magnetic neutron star
known as a magnetar before collapsing
into a black hole.
Troja's team, though, disagrees
that the observations require a white
dwarf. " I'd say that the origin of these
long GRBs is still very much open and
debated, " Troja says.
¢MONICA YOUNG
communications, Team Miles has sent
back radio signals. Like Lunar IceCube,
there have been no further updates.
While operational post-launch, the
LunIR satellite was unable to demonstrate
remote-sensing technology for
lunar science, sending back a weakerthan-expected
signal. And three missions
are missing from action entirely:
CuSP: The Cubesat for Solar Particles
was built to demonstrate space
weather data collection in heliocentric
orbit, but while CuSP was initially
deemed operational, its first contact
contained anomalies. The team since
lost contact but is still attempting communications
as of press time.
OMOTENASHI: Communications
from JAXA's small lunar lander
- officially named Outstanding Moon
Exploration Technologies demonstrated
by Nano Semi-Hard Impactor - were
unstable early on, and the spacecraft
began tumbling. The team has declared
the payload lost.
NEA Scout: NASA's Near-Earth
Asteroid (NEA) Scout was to deploy a
solar sail and rendezvous with the small
asteroid 2020 GE in late 2023, but the
mission never phoned home.
¢DAVID DICKINSON
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