Model of Fomalhaut b
expanding dust cloud2014
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Fomalhaut
and ring14 ASTRONOMY • AUGUST 2020
More than a decade ago, astrono-
mers believed they’d captured
the first direct image of a planet circling
another star. Dubbed Fomalhaut b, the
suspected world seemed to be orbiting a
star that’s a little hotter than the Sun and
located about 25 light-years away.
In the years that followed, researchers
used the Hubble Space Telescope to regu-
larly check in on the distant planet. But
then it started to dim, almost completely
disintegrating by 2014. And though there
are reasons why an exoplanet can fade,
they certainly don’t just disappear.
No, some Death Star-type spacecraft
didn’t decimate an entire planet. Instead,
according to new research published
April 20 in Proceedings of the National
Academy of Sciences, the world never
really existed. By piecing together shots
of Fomalhaut b over time, astronomers
realized that what they thought was an
exoplanet was actually just the remains
of a gigantic collision between icy objects.
“These collisions are exceedingly rare,
and so this is a big deal that we actually
get to see one,” said lead author András
Gáspár, an astronomer at the University
of Arizona, in a press release. “Our study,which analyzed all available archival
Hubble data on Fomalhaut b, includ-
ing the most recent images taken by
Hubble, revealed several characteristics
that together point to a picture that
the planet-sized object may never have
existed in the first place,” he added.
Based on the evolving shape and loca-
tion of the ejected debris, the researchers
estimate the original colliding bodies
were each likely a mix of ice and dust
measuring about 125 miles (200 kilome-
ters) in diameter.
Unfortunately, Hubble was late to the
main event, as the researchers think the
crash happened right before the telescope
began observing the system in 2004.
However, simply detecting the aftermath
of such a violent event is still exciting,
they say. According to the researchers’
calculations, massive collisions like this
may only happen once every 200,
years for any given system. — H.R.M.A SUSPECTED EXOPLANET
DISAPPEARS BEFORE HUBBLE’S EYES
THIS IS THE
DEFINITIVE
MOON MAP
Although humans have
gazed up at the Moon
since the dawn of our
existence, it wasn’t until
1959 that the Soviets’
Luna 3 spacecraft pro-
vided the first glimpse
of the lunar farside. And
now, for the first time
ever, the U.S. Geological
Survey, with the help of
NASA and the Lunar and
Planetary Institute, has
released a definitive map
of the entire lunar sur-
face. This orthographic
projection of the new map
highlights the complex
topography, geology, and
stratigraphy (rock layers)
of the Moon’s nearside
(top) and farside (bottom)
in incredible detail. — J.P.
QUANTUM GRAVITY
1,
The wind speed, in mph (2,293 km/h), measured on a brown
dwarf 40 times more massive than Jupiter. This is the first time
astronomers have measured wind speed on a brown dwarf.GOING, GOING, GONE. The star Fomalhaut is
surrounded by a vast ring of debris, as seen in
the composite image of the system (left) made
by combining many Hubble exposures. The
simulation-based image to the right shows the
evolving aftermath of a collision between two
minor bodies. NASA/ESA/A. GÁSPÁR AND G. RIEKE (UNIVERSITY OF
ARIZONA)NASA/GSF
C/
USGS