Sky & Telescope - December 2020 - 12

NEWS NOTES
ASTEROIDS

Potential New Targets for Hayabusa 2
proposal for an extended mission to one
of two asteroids after the spacecraft's
Earth flyby this December.
Launched in 2014, Hayabusa 2
arrived at Ryugu in 2018, collected
samples, and deployed two rovers and a
small lander, then departed in November 2019 (S&T: Mar. 2020, p. 10). The
spacecraft will pass by Earth on December 6, 2020, dropping off its samplereturn capsule in Australia.
With still about half of the xenon
thruster fuel remaining and the spacecraft in good shape, Japan Aerospace
Exploration Agency (JAXA) engineers
are now looking at options for sending
the mission to another target.
Possible asteroids, selected from an
initial field of 354 candidates, include
the oblong 2001 AV43 and the carbonaceous 1998 KY26. They're each about the
size of a baseball diamond, both circle
the Sun outside of Earth's orbit, and
both have a low enough speed relative

to the spacecraft to put them within
reach after December's flyby.
Both are also fast rotators, as evidenced by their light curves, each spinning on its respective axis once every 10
minutes. These asteroids are therefore
likely solid objects, rather than loosely
aggregated "rubble piles" like Ryugu
and 101955 Bennu are (the latter is the
target of NASA's Osiris-REX mission).
Hayabusa 2 could reach 2001 AV43 in
late 2029 or 1998 KY26 in mid-2031, if
the extended mission is approved.
Navigating to either asteroid would
involve Earth flybys, but reaching
2001 AV43 would also require a pass by
Venus. JAXA could use the Venus flyby
to carry out observations that would
complement data coming from the
Akatsuki orbiter.
Visiting either space rock would give
Japan the opportunity to test its technical capabilities of deep-space navigation
and planetary protection technology.
■ DAVID DICKINSON

Magnetic Fields in
Serpens South

Lick Observatory
Survives Wildfires

NEW DATA SHOW the complex role of

12

DECEMBER 2 02 0 * SK Y & TELESCOPE

The Arecibo Observatory in Puerto
Rico, one of the world's largest radio
telescopes, was damaged when one of
its auxiliary cables snapped, bringing
operations to a halt. No personnel were
injured. The damage occurred on August 10th at 2:45 a.m. local time, when
a 3-inch-thick cable snapped and fell,
opening a gash 30 meters (100 feet)
long in the 305-meter reflector dish.
The cable is one of many extending
from three towers, which support a
metal platform over the dish. Among
other things, the platform houses the
Gregorian dome, a reflector system
that focuses incoming radio waves.
The dish points at the zenith, but
thanks to the beam-steering mechanism in the dome Arecibo can aim at a
swath 20° north or south of this point,
expanding its view considerably. The
auxiliary cables and Gregorian dome
were added in an upgrade completed
in 1997. What caused the cable to
snap isn't immediately clear; engineers
are still gauging the damage and the
time needed for repairs.
■ DAVID DICKINSON

See images and drone video at
https://is.gd/Arecibodamage.

STARS

magnetic fields in star formation.
Thushara Pillai (Boston University) and colleagues used the HAWC+
instrument aboard the Stratospheric
Observatory for Infrared Astronomy
(SOFIA) to gauge magnetic field direction and strength in the Serpens South
stellar nursery, publishing the results
August 17th in Nature Astronomy.
Dense filaments of dust and gas
permeate the cluster. Previous measurements have shown that the magnetic
field tends to run parallel to lowerdensity filaments but perpendicular to
higher-density filaments. Magnetism
might moderate star formation by
counteracting the pull of gravity.
However, the new HAWC+ measurements taken by Pillai's team indicate
that along the densest, darkest fila-

Arecibo Observatory
Damaged

S This composite image of the Serpens South
star cluster shows magnetic field lines superimposed over an infrared background image.

ments in Serpens South, such as the
one at lower left in the image above, the
magnetic fields once again run parallel.
"In some dense filaments the magnetic
field succumbs to the flow of matter
and is pulled into alignment with the
filament," Pillai explains. The weakly
magnetized gas is feeding the growth of
new stars like a conveyor belt.
■ MONICA YOUNG

As the Santa Clara Unit Lightning
Complex fire swept east of San
Francisco Bay in California in late
August, flames threatened the historic
Lick Observatory, founded in 1888 on
nearby Mount Hamilton just outside
San Jose. The fire, which had already
burned nearly 400,000 acres, came
dangerously close to the main domes
around August 19-20. The fire came
within meters of the domes and was
clearly visible via the observatory's
webcam. However, the main observatory complex escaped major damage
and staff and residents are safe. A few
historic residences - including the
home of astronomer Edward Emerson
Barnard on Kepler Peak - were lost in
the conflagration.
■ DAVID DICKINSON

See how close the fire came at
https://is.gd/Lickfire.

N ASA / SOFIA / T. PILL AI / N ASA / JPL- CA LTECH / L. A LLEN

THE HAYABUSA 2 TEAM has laid out a

IN BRIEF


https://www.is.gd/Arecibodamage https://www.is.gd/Lickfire

Sky & Telescope - December 2020

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

Contents
Sky & Telescope - December 2020 - Cover1
Sky & Telescope - December 2020 - Cover2
Sky & Telescope - December 2020 - 1
Sky & Telescope - December 2020 - Contents
Sky & Telescope - December 2020 - 3
Sky & Telescope - December 2020 - 4
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