Sky & Telescope - March 2022 - 9

DART LAUNCH: NASA; PARKES: CSIRO / A. CHERNEY
SETI
IN BRIEF
The True Nature of
Proxima Centauri's
Candidate ET Signal
THE SIGNAL was the closest we've
come to thinking we had found intelligent
alien life. Discovered as part
of a 10-year initiative to find technosignature
in nearby star systems,
Breakthrough Listen Candidate 1 (or
BLC1) appeared to come from Proxima
Centauri, the nearest star to the Sun.
But in a pair of articles published
on October 25th in Nature Astronomy,
team members concluded that the signal
is of human origin.
BLC1 is the only signal to date that
checked the most important boxes for
alien origin. It was narrowband - a
tone purer than any natural process
could produce - and no known electronics
on Earth intentionally transmit
at that frequency. It also persisted over
several hours. What really made BLC1
exciting, though, was that its frequency
changed, drifting exactly as if it were
being emitted by something moving
within the Proxima Centauri system.
But when Breakthrough Listen
observed Proxima Centauri again in
2020 and 2021, BLC1 had disappeared.
After checking for human-made
interference from space and around the
observatory itself - and coming up dry
- the team tried a new strategy: They
searched for " lookalikes, " BLC1-like
signals detected when the telescope was
pointing somewhere else.
pThe Australian Parkes radio telescope, also
called by its Wiradjuri name Murriyang, detected
the signal of interest from Proxima Centauri.
Searching their data on hundreds of
other stars, the team turned up a few
dozen signals that drifted as BLC1 did,
though around different frequencies.
Critically, these signals also appeared
in off-source observations taken for
calibration. A single electronic device
interfering with itself could explain
these signals, the team found.
The new tools Breakthrough Listen
developed are essential to the search.
" We are really much more capable than
we were a few years ago, " says Michael
Garrett (University of Manchester, UK),
who wasn't involved in the study. " If
there is a signal out there, we're getting
closer to being able to detect it. "
And since Breakthrough Listen has
only searched thousands of stars out of
their goal of a million, plenty of opportunities
remain.
¢ASA STAHL
observing the spray of ejecta and possibly
the impact crater. Back on Earth,
astronomers will also watch the system,
carefully monitoring the light curve to
determine if Dimorphos's orbital period
around Didymos changes as expected.
In performing the first-ever experiNASA's
DART mission launches for a
head-on collision with an asteroid.
ment in changing an asteroid's velocity,
DART will deliver valuable lessons
toward that inevitable time in the
future when we need to move an asteroid
away from a population center.
¢EMILY LAKDAWALLA
An 'Oumuamua Analog?
When interstellar object 1I/'Oumuamua
was first spotted tumbling through the
solar system (S&T: Feb. 2018, p. 10), we'd
never seen anything like it. Among many
unexplained oddities was its shape: With
an aspect ratio of 6:6:1, it was basically
an otherworldly pancake. But at the Division
for Planetary Sciences meeting in
October, Ari Heinze (now at University of
Washington) reported preliminary results
for an asteroid, 2016 AK193, that behaves
remarkably like 'Oumuamua: It tumbles like
the interstellar object did, and it seems to
be just as elongated to boot. Unlike 'Oumuamua,
though, this asteroid is not a new
arrival; it has probably been going around
the Sun for billions of years. Follow-up observations
will take some patience, since
2016 AK193 won't come close enough to
observe again until 2029, Heinze says. Still,
the asteroid's mere existence is intriguing.
Its current near-Earth orbit is unstable over
100 million years, Heinze notes. So it's
possible this object used to belong to the
main belt before a gravitational encounter
redirected it, and that nudge might even
have precipitated its reshaping. More and
better observations will help us understand
this object's past.
¢MONICA YOUNG
Read more at https://is.gd/ssanalog.
Russia Conducts AntiSatellite
Test
A Russian missile struck a defunct satellite
early morning on November 15th, forcing
those aboard the International Space Station
(ISS) to take protective measures. The
crew sat out close debris passes in docked
spacecraft in case departure became
necessary. The U.S. State Department
and U.S. Space Command confirmed
and condemned the test later that day,
as did NASA. Roscosmos, the Russian
space agency, issued a brief statement
maintaining that the safety of the ISS crew
remains their main priority. At the time of
the test, there were 10 humans in space,
all in low-Earth orbit: seven aboard the ISS
(four from NASA, two from Roscosmos,
and one from the European Space Agency)
and three aboard China's Tiangong space
station. Other nations have also performed
anti-satellite tests, including China, the
U.S., and India. The current Outer Space
Treaty bans the use of nuclear weapons in
space but not anti-satellite tests.
¢DAVID DICKINSON
sk yand tele scope .o r g * MARCH 2022
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Sky & Telescope - March 2022

Table of Contents for the Digital Edition of Sky & Telescope - March 2022
