A
LTHOUGH MARS tends to get most
of the media attention, two spacecraft
continue to methodically explore a pair of
small, dark asteroids that occasionally come
reasonably close to Earth. Both Ryugu and
Bennu are little more than slowly spinning,
diamond-shaped, kilometre-wide piles of
rubble. Their boulder-strewn surfaces are
unexpectedly rugged and present serious
challenges to each spacecraft’s important
sample-return mission.
At Ryugu, Hayabusa2 managed to snag
a second sample on July 11, 2019, by firing
a tantalum bullet into the asteroid’s surface,
causing a spray of particles to be ejected
into space. Some of those Ryugu bits were
captured by Hayabusa2’s collection hornand safely stored. At least, that’s the hope.
Scientists won’t know for certain until the
capsule is opened after its return to Earth
in late 2020.
Meanwhile, OSIRIS-REx has been busy
surveying Bennu since December 2018.
The Canadian Space Agency’s OSIRIS-REx
Laser Altimeter spent several months scan-
ning Bennu’s surface, producing a highly
accurate three-dimensional model. Mission
scientists have designated four candidate
sample sites, and OSIRIS-REx is currently
performing a detailed reconnaissance of
each location. By the end of 2019, the pri-
mary and back-up sample-collection sites
will be selected. The collection attempt is
scheduled for the latter half of 2020.TWO PILES OF RUBBLE
A ROCKY WORLDScientists are preparing to extract samples from the rubbly surface of the
asteroid Bennu, above left. The four potential target locations are designated Nightingale, Kingfisher,
Osprey and Sandpiper—all birds native to Egypt, which complements the mission’s naming con -
ventions. The detailed image at left shows the site named Kingfisher (the white circle is 10 metres
in diameter).COURTESY NASA/GODDARD/UNIVERSITY OF ARIZONANOVEMBER/DECEMBER 2019 •SKYNEWS 7F
AST RADIO BURSTS (FRBs) are frac-
tion-of-a-second blasts of radio waves
produced by some unknown high-energy
process in deep space. First identified in
2007, FRBs are also one of astronomy’s lat-
est and greatest mysteries. Approximately
75 sources have been found, of which just
three were known to repeat—the rest ap-
pearing to be one-off flashes. But recently,
astronomers in the CHIME/FRB Collabo-
ration announced the discovery of eight
additional repeaters. All were detected using
CHIME, the Canadian Hydrogen Intensity
Mapping Experiment, an unusual half-
pipe-shaped radio telescope located near
Penticton, British Columbia.
Scientists can now compare and con-
trast signals from the 11 repeaters with sig-
nals from the one-off bursters. They can
also compare each of the repeating FRBs
to see how they differ from one another.
For instance, there is a significant variation
in the duration and number of repeti-
tions—six of the newly discovered FRBsrepeated only once, one repeated twice, and
another repeated 10 times.
On his Twitter feed, Bryan Gaensler of
the Dunlap Institute for Astronomy & Astro -
physics wrote that initial studies of these
new FRBs indicate they’re not all the same.
“Combine it with the fact that there are
possibly both repeaters and nonrepeaters,and it seems there might be a whole bunch
of different types of objects producing fast
radio bursts.” CHIME astronomers, he adds,
have discovered many more nonrepeating
FRBs and are currently preparing this result
for publication.
(Turn to page 10 of the May/June issue
for more on CHIME and FRBs.)FRB NETLocated in the dry interior of southern British Columbia, the CHIME radio tele-
scope recently detected eight new repeating fast radio bursts (FRBs). Here, the instrument
is seen by the light of a full Moon. COURTESY CHIME COLLABORATIONREPEAT AFTER ME