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SMAIRAMSPTWWW.ASTRONOMY.COM 31STORIES TO
WATCH FOR
IN 2020- The Mars 2020 mission is slated
to launch in July 2020, when Earth
and Mars are in close proximity and
travel time is relatively short. Its (as
yet unnamed) rover will explore Mars
with a new twist — it will set aside
rock and soil samples for future
return to Earth, where they can be
studied in better detail using terres-
trial labs. - Launched in 2016, the joint
European Space Agency-Roscosmos
ExoMars Trace Gas Orbiter is circling
the Red Planet in search of signs the
world was once habitable. It will be
joined by the agencies’ ExoMars
rover and surface science platform,
named Rosalind Franklin and
Kazachok, respectively, which also
will launch in July 2020. - ESA’s Solar Orbiter mission to study
solar and heliospheric physics will
launch in February 2020 as the agen-
cy’s first Cosmic Vision 2015–2025
Programme medium-class mission. It
will take about three years to reach
the Sun via gravity assists from Earth
and Venus. - In late 2020, ESA’s Gaia mission will
publish a portion of its third data
release, DR3. The early Gaia data
release, EDR3, will contain positions,
motions, and brightness information
of stars, as well as details about qua-
sars and other extended sources,
such as galaxies. - NASA’s OSIRIS-REx mission, cur-
rently at asteroid 101955 Bennu, is set
to physically sample the asteroid’s
surface in July 2020. During the five-
second maneuver, the spacecraft’s
Touch-and-Go Sample Acquisition
Mechanism will collect dust and
small pebbles, which will later be
returned to Earth. - In 2020, the Hubble Space
Telescope celebrates its 30th anni-
versary. The telescope was launched
aboard the space shuttle Discovery
on April 24, 1990, and released into
orbit one day later, on April 25.
astronomers’ expectations of what the
black hole should look like based on
Einstein’s theory of general relativity. “I
think what it tells us, at the very top level,
is that we have a lot of things right about
how black holes are accreting, how they’re
eating. But scientifically, interpretation-
wise and learning-wise, it’s kind of just the
start,” Marrone says. “It probably tells us
that we’ve measured the mass and that it’s
consistent with general relativity, but when
you’re testing Einstein, you don’t want
escape clauses. And there are still some
escape clauses in this. You could still come
up with ways that general relativity is
wrong but we’d still get this size. So we’re
still working on that, whether we’re really
testing general relativity,” he says.
One of the ways the EHT team is
working on that is through imaging
Sagittarius A* — the 4.3 million-solar-
mass black hole at the center of the Milky
Way. Those observations are also in hand,
but present yet another challenge. The
light from the material around a black
hole varies over time as that material shifts
and changes. The team observed such
changes, Marrone says, over the course of
a week with M87 and in pre-
vious VLBI observations of
the quasar 3C 279. Sagittarius
A* is about 1,500 times less
massive than M87’s black
hole. And smaller objects
undergo changes more
quickly — so what happened
on the order of a week in M87,
Marrone says, happens on the
scale of minutes in Sagittarius
A*. “I think the best general
relativity test comes from Sagittarius A*,”
he says. But “figuring out how to deal with
a source that changes while we’re looking
at it is a bigger deal” than taking any more
data at this point, he says.
The team is also still looking to learn
more about how M87’s black hole gener-
ates and launches its huge jet of high-
energy particles, which spans about
5,000 light-years. That information,
Marrone says, will likely come from
analysis of how the light around the
black hole is oriented, called polarization,
which is also yet to come.
Although there is always more work to
be done, EHT’s accomplishment was
unparalleled in 2019, earning it our top
spot. “It’s been my belief for a lot of years
that we could technically do this,”
Marrone says, “but I had no idea what we
would see.” Actually imaging the region
immediately around a black hole and
capturing its shadow not only confirms
our understanding of the extreme physics
at play around these objects, but also
serves as a springboard to better under-
standing how they form, how they act,
and the role they play in our universe.Alison Klesman is an associate
editor of Astronomy magazine who
is excited to see what astronomers
will accomplish in 2020.To zoom in on a black hole, the Event Horizon Telescope Collaboration linked eight radio telescopes from
around the world to form a virtual radio dish the size of our planet. The Greenland Telescope (GLT) was not
part of the array that imaged M87, but has since joined EHT for future observing campaigns. ESO/O. FURTAK