Sky & Telescope - September 2020 - 13

EXOPLANETS

Astronomers Snap Baby
Planet's Picture
ASTRONOMERS HAVE WITNESSED

the turbulent swirls of planet formation
around the several-million-year-old star
AB Aurigae, 530 light-years away in the
constellation Auriga, the Charioteer.
Previous observations with the
Atacama Large Millimeter/submillimeter Array (ALMA) in Chile had shown
spirals within a vast, 120-a.u. gap in
the disk of dust and gas surrounding the central star. The gap, and the
gaseous spirals within it, had hinted at
fast-growing newborn planets, but they
didn't provide deﬁnitive evidence of
their existence.
Now, Anthony Boccaletti (Observatory of Paris) and colleagues have taken
closer-in and more sensitive observations using the Spectro-Polarimetric
High-contrast Exoplanet Research
(SPHERE) instrument on the European
Southern Observatory's Very Large
Telescope, showing the suspected planet
formation in action. The results appear
in the May Astronomy & Astrophysics.
SPHERE uses a coronagraph and
special techniques to negate the light

SPACE BRIEFS

ESO / BOCCA LE T TI E T A L. (2)

SpaceX Lofts "VisorSat"
SpaceX has revealed details on its plans to
darken its Starlink megaconstellation, which
will ultimately contain up to 42,000 satellites.
The document, posted on the Starlink website, clarifies which parts make the satellites
so bright (the solar panels, though shiny, are
not the culprit). SpaceX had attempted to
darken one of its satellites with a specialized
coating on its phased array and parabolic
antennas, but it did not reduce the reflections
enough. The company is now implementing
two different fixes: a software change will dim
satellites raising their orbits by turning their
solar panels to reflect less sunlight, while additional hardware - a deployable visor - will
prevent sunlight from reflecting off other parts
of the satellites once they reach their operational altitude. The first "VisorSat" launched
on June 3rd.
■ MONICA YOUNG

p Left: In this SPHERE image, AB Aurigae is blocked out at the center, revealing the disk around
it. Right: Astronomers think a planet is forming in the bright yellow swirl, seen just below the center
in this close-up of the system.

shows that the smear appeared there,
too - and it has since then rotated
around its star in a way that's consistent with it being in orbit.
"The twist is expected from some
theoretical models of planet formation,"
explains coauthor Anne Dutrey (Laboratory of Astrophysics of Bordeaux,
France). "It corresponds to the connection of two spirals - one winding
inwards of the planet's orbit, the other
expanding outwards - which join at the
planet location."
The researchers say that, because the
gap in the disk around AB Aurigae is so
vast, there could be more planets, as yet
unseen, forming within the cavity.

coming from the bright central star,
revealing ﬁne detail in the dust-and-gas
disk around it. SPHERE's image shows
that the spiral arms previously seen by
ALMA continue inward toward the star.
Nestled within one of these arms is a
smear of light - a planet likely several times Jupiter's mass that's coming
together within the S-shape swirl.
The actual mass depends on how
fast the object is growing, though; the
forming object might be too massive to
be a planet.
Whatever the forming object is, it's
at 30 a.u. from its star, putting it at
roughly the same distance that Neptune
orbits the Sun. Indeed, comparison with
the ALMA images from four years ago

■ MONICA YOUNG

U.S. Launches Space Crew

The Roman Space Telescope

On May 30th, a SpaceX Falcon 9 rocket carried the new Crew Dragon capsule on its first
crew-carrying flight - and the first launch to
come from American soil since the retirement of NASA's Space Shuttle program in
2011. NASA astronauts Robert Behnken and
Douglas Hurley, both shuttle veterans, flew
to the International Space Station (ISS). The
first non-test flight, slated for August 30th, will
carry four expedition crew members. NASA
has contracted commercial flights with both
SpaceX and Boeing, offering them $2.6 billion
and $4.2 billion, respectively. Each company
is to fly six operational missions to the ISS.
SpaceX will carry out its assigned missions
through 2021. Boeing launched and landed
an uncrewed Starliner capsule in late 2019,
but it failed to reach the station. The company
plans to carry out a second uncrewed demo
flight in the fall.
■ DAVID DICKINSON

NASA has renamed its Wide Field Infrared
Survey Telescope (WFIRST) the Nancy Grace
Roman Space Telescope, the first space telescope to honor a woman in the field. Known
as the "Mother of Hubble," Roman (1925-
2018) was NASA's first chief astronomer.
Under her leadership, NASA launched several
astronomical observatories. She played a key
role in developing the International Ultraviolet
Explorer and the Cosmic Background Explorer. Her primary legacy, though, was paving the way for the Hubble Space Telescope.
Now, the Roman Space Telescope is set to
follow the James Webb Space Telescope into
orbit, using infrared light to probe the nature
of dark energy as well as hunt for exoplanets.
The $3.2 billion mission is currently only funded through September 2020. It is not included
in the president's FY2021 budget request,
which Congress has not yet approved.
■ DAVID DICKINSON
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Sky & Telescope - September 2020

Table of Contents for the Digital Edition of Sky & Telescope - September 2020