University of Manchester astronomers, as part of a world-wide collaboration,
have discovered the youngest known radio-emitting pulsar. They used the
world’s largest fully steerable radio telescope to detect remarkably faint
radio signals from an 820 year-old pulsar associated with a supernova
remnant located 10,000 light years away in the constellation Cassiopeia.
This is one of the first key discoveries made by the newly commissioned,
105-m diameter, Robert C. Byrd, Green Bank Telescope located in West
Virginia, USA. This discovery, the result of the most sensitive radio
observations ever made in the search for pulsars, will enable scientists to
conduct further observations that could lead to a better understanding of
how these stellar remnants evolve.

“Important questions about pulsars may be answered by long-term monitoring
of objects such as the one we have just detected,” said the group leader
Fernando Camilo of Columbia University in New York City. “Young pulsars are
particularly rare, and being able to study such a young one at radio
wavelengths provides an outstanding opportunity to learn critical facts
about their evolution and workings.”

Scientists have long suspected that a pulsar – a rapidly spinning,
superdense neutron star – was born when a giant star ended its life in a
cataclysmic supernova explosion observed in late summer of 1181, as
suggested by Japanese and Chinese historical records. For the past 20 years,
astronomers have searched this supernova remnant (3C58) for the telltale
pulsations of the pulsar. Late in 2001, data from NASA’s Chandra X-ray
satellite confirmed its existence, but it remained an elusive quarry for
radio telescopes.

“We believed from historical records and certainly knew from recent X-ray
observations that this star was there,” Camilo remarked, “but despite many
attempts, no one had been able to find any radio pulsations from it because
the signals are, it turns out, incredibly weak.” For comparison, this
pulsar’s radio emission is some 250 times weaker than that from the famous
pulsar in the Crab Nebula (the remnant of an explosion in the year 1054
recorded by Chinese astronomers).

“Although we knew what we were searching for,” said Ingrid Stairs, team
member from NRAO Green Bank, “it took the new Green Bank Telescope with its
unmatched sensitivity — and, importantly, location in a National Radio
Quiet Zone — to make this remarkable detection.” The newly detected pulsar,
known as PSR J0205+6449, is currently rotating 15 times every second.

By detecting this pulsar in the radio part of the spectrum, astronomers may
now follow its evolution with greater ease and flexibility than with X-ray
telescopes on satellites, study the pulsar emission mechanisms, and also
characterize the dynamic interstellar medium between the Earth and the
pulsar.

“Continued observations of such a young radio pulsar will provide a mine of
information for years to come,” noted Duncan Lorimer of the University of
Manchester. “We will be able to precisely track how its rate of rotation
changes over time, potentially inferring fundamental clues about what causes
a magnetized neutron star to spin down. We also be able to make valuable
comparisons to the X-ray data, which may help us determine exactly how and
where these stars generate and emit radiation.”

The researchers also point to the fact that this discovery bodes well for
the Green Bank Telescope being able to study additional young pulsars that
have previously escaped detection. “By using this magnificent new telescope,
we should be able to discover other very young pulsars that we surmise are
there, but are simply too weak to detect by any other means,” said Camilo.
“Measuring the luminosity and spectrum of a large sample of these stars will
be crucial for making an accurate census of pulsars in our Galaxy.”

The researchers used the new Berkeley-Caltech Pulsar Machine designed by
Donald C. Backer at UC Berkeley to process the signals from the GBT and
record them for later analysis using software written primarily by the
research team members at the University of Manchester.

The group led by Camilo in this investigation consists also of: Ingrid H.
Stairs (NRAO Green Bank, West Virginia); Duncan R. Lorimer, Michael Kramer,
Maura A. McLaughlin (University of Manchester, Jodrell Bank Observatory,
Cheshire, U.K.); Donald C. Backer (University of California, Berkeley);
Scott M. Ransom (McGill University, Montreal, Canada); Bernd Klein, Richard
Wielebinski, Peter Muller (Max-Planck-Institut fur Radioastronomie, Bonn,
Germany); and Zaven Arzoumanian (Universities Space Research
Association/NASA-Goddard Space Flight Center, Greenbelt, Maryland).

Contact details:

Dr. Duncan Lorimer, University of Manchester, Jodrell Bank Observatory,

Cheshire, UK

Phone: +44-1477-572-675

e-mail: drl@jb.man.ac.uk

Dr. Fernando Camilo, Columbia University, USA.

Phone: +1-212-854-2540

e-mail: fernando@astro.columbia.edu

Dr. Ingrid Stairs, NRAO Green Bank, West Virginia, USA

Phone: +1-304-456-2213

e-mail: istairs@nrao.edu

Images may be downloaded from the following URL:

http://www.jb.man.ac.uk/news/youngpulsar/

Further information:

A pulsar is formed when a massive star runs out of nuclear fuel and dies in
a cataclysmic explosion called a supernova. The outer layers of the star are
blown off into space, and are often seen as an expanding remnant shell of
hot gas. The core of the star, with 40 percent more mass than our Sun,
collapses under its own gravity to a sphere only about 10 miles in diameter,
composed mostly of neutrons. These, the densest objects known in the
Universe, are typically born spinning very rapidly. They have very powerful
magnetic and electric fields that accelerate electrons and other subatomic
particles, causing them to emit beams of radio waves, X-rays, and other
forms of radiation. If these beams intersect the Earth as the star rotates,
we can then detect the pulsar, as it appears to flash on-and-off, much like
a lighthouse. As the pulsar ages, it gradually slows down and loses its
rotational energy. After a few million years it is no longer powerful enough
to generate radio emission and “turns-off.”

The Green Bank Telescope is the world’s largest fully steerable radio
telescope. It was dedicated on August 25, 2000. It is a major instrument of
the National Radio Astronomy Observatory, a facility of the National Science
Foundation, operated under cooperative agreement by Associated Universities,
Inc.