Sky & Telescope - October 2019 - 9

IN BRIEF
Sun-Studying Missions
Selected
NASA has selected two missions to study
the Sun-Earth connection. The Polarimeter to Unify the Corona and Heliosphere
(PUNCH) consists of four suitcase-size
satellites known as microsats that will fly in
formation in low-Earth orbit while investigating the solar wind as it leaves the Sun.
The spacecraft will also track coronal mass
ejections, the solar wind tsunamis that
sometimes hurtle toward Earth, affecting
satellite communications. PUNCH gains
3D information about these events by
photographing sunlight that has become
polarized as it bounces off electrons in
the solar wind. Sharing PUNCH's ride to
space, the two spacecraft that make up
the Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites
(Tracers) will study the Sun-Earth connection a bit closer to home, focusing on the
regions where the Sun's magnetic field
interacts with Earth's field. NASA selected
both missions for development and flight
through its Heliophysics Small Explorers
Program. They will cost no more than $165
million and $115 million, respectively, and
will launch no later than August 2022.
■ MONICA YOUNG

For more details about the missions,
visit https://is.gd/Helio.

ESA's Comet Interceptor

CSIRO

The European Space Agency has selected
a mission to accompany its exoplanethunting satellite, ARIEL, when it's launched
in 2028. The Comet Interceptor will consist
of three solar-powered spacecraft that
will travel with ARIEL to Lagrangian point
L2 1.5 million km (1 million miles) beyond
Earth, on the opposite side from the Sun.
The Comet Interceptor will wait there while
looking for a target: either a new comet or
perhaps an interstellar comet like 'Oumuamua. Once a target is identified, all three
spacecraft will fly toward it together before
separating to view it from different vantage
points. Comets previously explored by
spacecraft have returned again and again
to the inner solar system, and solar heating
has disturbed and altered their surfaces.
The Comet Interceptor concept will enable
scientists to explore a comet making its
first trip toward the Sun; such an object
could provide a pristine sample of the outermost reaches of the solar system.
■ MONICA YOUNG

Find more mission details at
https://is.gd/CometInterceptor.

FAST RADIO BURSTS

Two More Flashes' Host Galaxies Found
ASTRONOMERS HAVE HOMED IN on
the host galaxies of two non-repeating
fast radio bursts (FRBs, S&T: July 2016,
p. 24), and their homes are not what the
teams expected.
Until recently, astronomers have
only been able to identify the host
galaxy of FRB 121102 - one of only two
FRBs known to flash repeatedly. But
on June 27th, Keith Bannister (CSIRO,
Australia) and colleagues reported in
Science that they had found the source
of FRB 180924 - a millisecond-long
flash that hasn't repeated - using the
36-dish Australian Square Kilometer
Array Pathfinder (ASKAP). Then, on
July 2nd, Vikram Ravi (Caltech) and
colleagues announced that they'd narrowed down the galaxy hosting a second
non-repeater, FRB 190523. Both teams
triangulated the sources using radio
interferometry.
In observations from the Dark
Energy Survey, the Very Large Telescope and the Gemini South Telescope
in Chile, and the Keck II Telescope
in Hawai'i, Bannister and colleagues
spotted the host galaxy, which appears
to be lenticular in shape. Its light took
3.6 billion light-years to arrive at Earth.
Spectroscopic measurements show little
evidence of new stars forming; moreover, the burst appears to come from
the galaxy's anemic outer reaches.
Meanwhile, Ravi's team used a
10-dish prototype for the upcoming

p ASKAP is one of the pathfinder radio arrays
involved in homing in on the host galaxies of fast
radio bursts.

Deep Synoptic Array at the Owens
Valley Radio Observatory in California
to quickly home in on FRB 190523. A
deep image and spectroscopy of the field
via the Keck I Telescope shows a Milky
Way-size galaxy with a Milky Way-like
star-formation rate (about one Sun per
year). If the source is in this galaxy,
then its radio waves have traveled more
than 6 billion light-years to Earth. Their
study will appear in Nature.
These findings are in stark contrast to the home of the repeating
FRB 121102: a compact star-forming
region in a dwarf galaxy (S&T: Sept.
2017, p. 12). Given its environment,
some astronomers think its pulses
might come from a newborn, highly
magnetized neutron star known as a
magnetar. However, the location of the
non-repeating FRBs in galaxies with
little or no star formation suggests that
their sources are not associated with
new stars, magnetars or otherwise.
"Interestingly, both host galaxies of
FRB 180924 and FRB 190523 are more
similar to each other than they are to
the host of FRB 121102 (the repeater),"
says Bannister. Different scenarios
might apply to repeating and nonrepeating bursts.
■ MONICA YOUNG
sk yandtele scope.com * OCTOBE R 2 019

9


https://www.is.gd/Helio https://is.gd/CometInterceptor http://www.skyandtelescope.com

Sky & Telescope - October 2019

Table of Contents for the Digital Edition of Sky & Telescope - October 2019

Contents
Sky & Telescope - October 2019 - Cover1
Sky & Telescope - October 2019 - Cover2
Sky & Telescope - October 2019 - 1
Sky & Telescope - October 2019 - Contents
Sky & Telescope - October 2019 - 3
Sky & Telescope - October 2019 - 4
Sky & Telescope - October 2019 - 5
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