Sky & Telescope - April 2022 - 10

NEWS NOTES
BLACK HOLES
Nearest Supermassive
Black Hole Pair Discovered
ASTRONOMERS HAVE IDENTIFIED
and " weighed " the nearest dual supermassive
black hole in a galaxy 89 million
light-years away.
In a study to appear in Astronomy &
Astrophysics, a team led by Karina Voggel
(Observatory of Strasbourg, France)
presents evidence that a previously discovered
double nucleus at the center of
the slightly distorted galaxy NGC 7727
harbors two supermassive black holes
some 1,600 light-years apart. That's
close enough for them to collide within
just 250 million years or so.
Using the Multi Unit Spectroscopic
Explorer (MUSE) on the European
Southern Observatory's Very Large Telescope
in Chile, the team measured the
bulk stellar motions in the two nuclei.
The spread of velocities indicates that
the black holes have 154 million and
6.3 million solar masses, respectively.
" This is a nice piece of work and a
very trustworthy way of determining
SPACE
What Comes after the International Space Station?
AS NASA PREPARES to retire the
International Space Station (ISS) by
2030, it will also support a transition
to commercial operations in low-Earth
orbit. This recommendation comes as
part of an audit that the NASA Office of
Inspector General released on November
30, 2021.
The station has hosted a continuous
human presence in space since
November 2, 2000, and it has served
as a key platform for scientific studies
in fields ranging from human physiology
to Earth observation to high-energy
astrophysics. But the station is showing
its age. Most notably, multiple cracks
and additional undiscovered leaks
along the interior of the Service Module
Transfer Tunnel, which connects to one
of the areas where crew live and work,
have raised concerns about the station's
structural integrity.
10 APRIL 2022 * SKY & TELESCOPE
The report thus details the plan for
a controlled deorbit, which will take
place over several years beginning
between 2026 and 2028. (In the event
of an emergency, the reentry timeline
could accelerate to about six months.)
Deorbiting the station will cost about
$1 billion (roughly the same as one
year's maintenance), to be split among
the international partners.
The audit acknowledges that research
pThis image shows close-up (left) and wide (right) views of the two bright nuclei of NGC 7727, each
of which harbors a supermassive black hole.
the black hole masses, " comments Peter
Barthel (University of Groningen, The
Netherlands).
The duo is one of a growing number
of supermassive black hole pairs that
astronomers have found. Since galaxies
grow via mergers and most large galaxies
host supermassive black holes, we
can expect to see many such pairs, but
they can be hard to find. Voggel points
out that the more massive black hole in
NGC 7727 doesn't show any current
activity, so it would have gone unnoticed
if not for the velocity measurements
carried out with MUSE.
" Due to these hidden black holes,
some of which may be outside of the
centers of galaxies, the overall number
of supermassive black holes could
be up to 30% higher than previously
assumed, " Voggel notes.
¢GOVERT SCHILLING
on the long-term effects of living in
space, essential to future missions, will
not finish before the ISS's demise. Other
outposts will therefore have to continue
to advance the work.
To that end, NASA has selected three
companies to develop plans for commercial
stations in low-Earth orbit,
including Blue Origin ($130 million),
Nanoracks LLC ($160 million), and
Northrop Grumman ($125.6 million).
Axiom Space is another player in
commercial low-Earth orbit. The company
plans to send at least one module
to the ISS in late 2024, which will
detach and form its own small space
station by 2028.
For years, the ISS has silently slid
pThe International Space Station, as viewed
from the Space Shuttle
overhead in the night, a reminder of
humanity's outpost in space. With
preparation, that human presence may
continue for decades to come.
¢DAVID DICKINSON
Read the full report at https://is.gd/
ISSaudit.
NGC 7727: ESO / VOGGEL ET AL. / ASTRONOMY & ASTROPHYSICS 2021; ISS: NASA

https://www.is.gd/issaudit https://www.is.gd/issaudit

Sky & Telescope - April 2022

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