CTB 1, seen here in a deep
exposure that highlights visible light from hydrogen gas, is the
expanding wreckage of a massive star that exploded some 10,000 years
ago. The pulsar formed in the center of the collapsing star is moving so
fast it has completely exited the faint shell. Credit: Copyright Scott Rosen, used with permission. Hi-re image
Astronomers found a pulsar hurtling through space at nearly 2.5
million miles an hour — so fast it could travel the distance between
Earth and the Moon in just 6 minutes. The discovery was made using
NASA’s Fermi Gamma-ray Space Telescope and the National Science
Foundation's Karl G. Jansky Very Large Array (VLA).
Pulsars are superdense, rapidly spinning neutron stars left behind
when a massive star explodes. This one, dubbed PSR J0002+6216 (J0002 for
short), sports a radio-emitting tail pointing directly toward the
expanding debris of a recent supernova explosion.
“Thanks to its narrow dart-like tail and a fortuitous viewing angle,
we can trace this pulsar straight back to its birthplace,” said Frank
Schinzel, a scientist at the National Radio Astronomy Observatory (NRAO)
in Socorro, New Mexico. “Further study of this object will help us
better understand how these explosions are able to ‘kick’ neutron stars
to such high speed.”
New radio observations combined with 10 years of
data from NASA’s Fermi Gamma-ray Space Telescope have revealed a runaway
pulsar that escaped the blast wave of the supernova that formed it. Credits: NASA’s Goddard Space Flight Center. Download this video in HD formats from NASA Goddard's Scientific Visualization Studio
The CTB 1 supernova remnant resembles a ghostly
bubble in this image, which combines new 1.5 gigahertz observations from
the Very Large Array (VLA) radio telescope (orange, near center) with
older observations from the Dominion Radio Astrophysical Observatory’s
Canadian Galactic Plane Survey (1.42 gigahertz, magenta and yellow; 408
megahertz, green) and infrared data (blue). The VLA data clearly reveal
the straight, glowing trail from pulsar J0002+6216 and the curved rim of
the remnant’s shell. CTB 1 is about half a degree across, the apparent
size of a full Moon. Credits: Composite by Jayanne English, University
of Manitoba, using data from NRAO/F. Schinzel et al., DRAO/Canadian
Galactic Plane Survey and NASA/IRAS. Hi-res image
Schinzel, together with his colleagues Matthew Kerr at the U.S. Naval
Research Laboratory in Washington, and NRAO scientists Dale Frail,
Urvashi Rau and Sanjay Bhatnagar presented the discovery at the High
Energy Astrophysics Division meeting of the American Astronomical
Society in Monterey, California. A paper describing the team’s results
has been submitted for publication in a future edition of The
Astrophysical Journal Letters.
Pulsar J0002 was discovered in 2017 by a citizen-science project called Einstein@Home,
which uses time on the computers of volunteers to process Fermi
gamma-ray data. Thanks to computer processing time collectively
exceeding 10,000 years, the project has identified 23 gamma-ray pulsars
to date.
Located about 6,500 light-years away in the constellation Cassiopeia, J0002 spins 8.7 times a second, producing a pulse of gamma rays with each rotation.
The pulsar lies about 53 light-years from the center of a supernova
remnant called CTB 1. Its rapid motion through interstellar gas results
in shock waves that produce the tail of magnetic energy and accelerated
particles detected at radio wavelengths using the VLA. The tail extends
13 light-years and clearly points back to the center of CTB 1.
Using Fermi data and a technique called pulsar timing, the team was
able to measure how quickly and in what direction the pulsar is moving
across our line of sight.
“The longer the data set, the more powerful the pulsar timing
technique is,” said Kerr. “Fermi’s lovely 10-year data set is
essentially what made this measurement possible.”
The result supports the idea that the pulsar was kicked into high
speed by the supernova responsible for CTB 1, which occurred about
10,000 years ago.
J0002 is speeding through space five times faster than the average
pulsar, and faster than 99 percent of those with measured speeds. It
will eventually escape our galaxy.
At first, the supernova’s expanding debris would have moved outward
faster than J0002, but over thousands of years the shell’s interaction
with interstellar gas produced a drag that gradually slowed this motion.
Meanwhile, the pulsar, behaving more like a cannonball, steadily raced
through the remnant, escaping it about 5,000 years after the explosion.
Exactly how the pulsar was accelerated to such high speed during the
supernova explosion remains unclear, and further study of J0002 will
help shed light on the process. One possible mechanism involves
instabilities in the collapsing star forming a region of dense,
slow-moving matter that survives long enough to serve as a
“gravitational tugboat,” accelerating the nascent neutron star toward
it.
The team plans additional observations using the VLA, the National Science Foundation’s Very Long Baseline Array (VLBA) and NASA’s Chandra X-ray Observatory.
The National Radio Astronomy Observatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc.
The Fermi Gamma-ray Space Telescope is an astrophysics and particle
physics partnership managed by NASA's Goddard Space Flight Center in
Greenbelt, Maryland. Fermi was developed in collaboration with the U.S.
Department of Energy, with important contributions from academic
institutions and partners in France, Germany, Italy, Japan, Sweden and
the United States.
By Francis Reddy
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Editor: Rob Garner
Source: NASA/Fermi Space Telescope
