Sky & Telescope - September 2022 - 11

SXS LENSING
GRAVITATIONAL WAVES
IN BRIEF
10 New Black Hole Mergers Found in LIGO Data
THE LIGO, VIRGO, AND KAGRA (LVK)
collaboration has so far tallied 90
gravitational-wave events, almost all of
which were mergers of two black holes.
But LVK researchers aren't the only ones
trawling the data.
One team that applies its own
analysis techniques has its hub at the
Institute for Advanced Studies (IAS).
These researchers have now taken their
own look at the first half of the third
observing run and turned up 10 new
candidate mergers. They also recovered
one that LVK collaborators had found
and dismissed, Seth Olsen (Princeton)
reported at the April meeting of the
American Physical Society.
But we can't simply add these
11 events to the total. To tease out
minuscule signals from all the noise,
researchers use pipelines, chains of computing
processes that clean and assess
data. Choices made in these pipelines
determine which of the signals will
pop out of the background. The IAS
team's pipeline improves on computing
efficiency but also ignores some of the
loudest (and most likely) events in order
to be more sensitive to quieter, and
potentially more exotic, ones.
Thanks to these choices, the IAS
pipeline " lost " six events from the
observing run but gained 11 new ones.
pA simulated image of the merger of a blackhole
binary
Statistically speaking, however, three
of the new detections are likely to be
flukes rather than real events.
The new candidates include several
mergers of black holes with masses both
above and below the expected ranges:
One involved a monster 80-solar-mass
black hole, while another involved a
tiny object (a black hole or a massive
neutron star) of 2.1 to 4.4 solar masses.
The LVK collaboration keeps track
of events that independent teams find
and compares those analyses to its
own. " We are delighted that people
look at the data from new perspectives
and with new tools, " says LIGO
spokesperson Patrick Brady (University
of Wisconsin, Milwaukee). Some events
are added to the LVK catalog if the collaboration
can confirm them using its
own methods. Such additions must be
done carefully to enable clean analyses
of the merger population.
LVK researchers are now turning
their attention to the fourth observing
run, set to begin in December. With
upgrades to sensitivity, they expect to
detect a merger every few days. As the
events stack up, oddballs and subclasses
will become more explorable.
¢CAMILLE M. CARLISLE
Insight at Mars: Monster
Quake, Powering Down
NASA's Insight Mars lander witnessed the
biggest quake yet in the nick of time - just
before the craft began to run low on power.
The record-breaker wasn't strong by Earth
standards, but it was the strongest temblor
recorded on another planet. The Seismic
Experiment for Interior Structure aboard Insight
noted the 5th-magnitude marsquake
on May 4, 2022. Three days later, increasing
dust in the air and on the solar panels
caused the lander's power levels to drop.
The mission entered a preemptive safe
mode on May 7th but is back to collecting
seismic data as of press time. NASA has
approved an extended mission through
December 2022, with most power being
prioritized for the seismometer. To date, Insight
has detected more than 1,313 marsquakes
and has achieved the top science
goals for its two-year primary mission. The
quakes have enabled scientists to probe
the Martian interior: So far, researchers
have put the radius of the planet's core at
1,830 km (1,137 miles), and they've estimated
that the crust could extend as deep
as 37 km (S&T: Nov. 2021, p. 8). Analysis
of new temblors could reveal additional
details about the structure of Mars's crust,
mantle, and core.
¢DAVID DICKINSON
Tau Herculids: A New
Meteor Shower
In the fall of 1995, Comet 73P/Schwassmann-Wachmann
3 fractured into several
pieces and left a trail of fragments in its
wake. In the May issue of Sky & Telescope,
I reported that Earth might encounter this
stream of debris during the overnight hours
of May 30-31. The possible scenarios included
a brief outburst of meteors ranking
with some of our richest annual displays
(Geminids and Perseids), perhaps even
amounting to a meteor storm. On the flip
side, the uncertainties inherent in such
calculations meant that we might only
encounter very few comet particles - or
none at all. The reality, as so often happens,
was something in between. Observers
at clear and dark sites reported seeing
dozens of meteors per hour, with many
bright, slow-moving shower members,
some of them leaving a smoky train. Unfortunately
for those who were hoping for a
major outburst, or even a meteor storm, it
was not to be.
¢JOE RAO
sk yand tele scope .o r g * SEPTEMBER 2022 11
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Sky & Telescope - September 2022

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