An international team of scientists from the UK, Australia, Italy and the USA
have announced in today’s issue of the journal Science Express (8th January
2004) the first discovery of a double pulsar system.

They have shown that the compact object orbiting the 23-millisecond pulsar PSR
J0737-3039A with a period of just 2.4 hours is not only, as suspected, another
neutron star but is also a detectable pulsar, PSR J0737-3039B, that is rotating
once every 2.8 seconds.

Professor Andrew Lyne of the University of Manchester points out that "While
experiments on one pulsar in such an extreme system as this are exciting enough,
the discovery of two pulsars orbiting one another opens up new precision tests
of general relativity and the probing of pulsar magnetospheres."

The same team previously reported [Nature 4th December 2003], the discovery of
pulsar A in a close binary system which is rapidly losing energy by
gravitational radiation. The stars will coalesce in only approximately 85
million years, sending a ripple of gravity waves across the Universe. The
discovery of the system shows that such coalescences will occur more frequently
than previously thought. "The news has been welcomed by gravitational wave
hunters, since it boosts their hopes for detecting the gravitational waves" says
Prof. Nichi D’Amico of Cagliari University.

The double neutron star system was first detected using the 64-m Parkes radio
telescope in New South Wales, Australia. Subsequent observations were made both
at Parkes and with the 76-m Lovell Telescope of the University of Manchester in
Cheshire, UK and revealed the occasional presence of pulsations with a period of
2.8 seconds from the companion pulsar.

Already, four different effects beyond those explained with simple Newtonian
gravity have been measured and are completely consistent with Albert Einstein’s
theory. Dr. Richard Manchester of the Australia Telescope National Facility
says, "The fact that both objects are pulsars enables completely new
high-precision tests of gravitational theories. This system is really extreme."
Future observations of the two stars will measure their slow spiral in towards
each other as they radiate gravitational radiation — a dance of death leading
to their ultimate fusion into what may become a black hole. General relativity
predicts that the two stars will slowly wobble like spinning tops allowing new
tests of the theory.

Another unique aspect of the new system is the strong interaction between
radiation from the two stars. By chance, the orbit is seen nearly edge on to us,
and the signal from one pulsar is eclipsed by the other. Dr. Andrea Possenti of
Cagliari Astronomical Observatory says, "This provides us with a wonderful
opportunity to probe the physical conditions of a pulsar’s outer atmosphere,
something we’ve never been able to do before."

The surveys designed by the team to discover new pulsars at the Parkes Telescope
have been extraordinarily successful. They have discovered over 700 pulsars in
the last 5 years, nearly as many as were discovered in the preceding 30 years.
The discovery of this double pulsar system will be the major jewel in the crown.


A.G. Lyne, M. Burgay, M. Kramer, A. Possenti, R.N. Manchester, F. Camilo, M.A.
McLaughlin, D.R. Lorimer, N. D’Amico, B.C. Joshi, J. Reynolds and P.C.C. Freire.
"A Double-Pulsar System – A Rare Laboratory for Relativistic Gravity and Plasma
Physics". Science 8 January 2004.

Background information

A pulsar is the collapsed core of a massive star that has ended its life in a
supernova explosion. Weighing more than our Sun, yet only 20 kilometres across,
these incredibly dense objects produce beams of radio waves which sweep round
the sky like a lighthouse, often hundreds of times a second. Radio telescopes
receive a regular train of pulses as the beam repeatedly crosses the Earth so
the objects are observed as a pulsating radio signal.

Pulsars make exceptional clocks, which enable a number of unique astronomical
experiments. Some very old pulsars, which have been "spun up" to speeds of over
600 rotations per second by material flowing onto them from a companion star,
appear to be rotating so smoothly that they may even "keep time" more accurately
than the best atomic clocks here on Earth. Very precise timing observations of
systems in which a pulsar is in orbit around another neutron star have been able
to prove the existence of gravitational radiation as predicted by Albert
Einstein and have provided very sensitive tests of his theory of General
Relativity — the theory of gravitation which supplanted that of Isaac Newton.
The neutron star binary system reported in this paper is one of these systems,
with an orbit which is decaying more rapidly than any previously discovered.

The Parkes survey using a multi-beam system that led to the discovery of the
double-pulsar system is an international collaboration of a team of astronomers
from the UK, Australia, Italy and the USA. The researchers have been surveying
our Galaxy, the Milky Way, for new radio pulsars using the 64-metre Parkes Radio
Telescope in New South Wales, Australia. The powerful new "multibeam" receiver
was built as a joint venture between engineers at the Australia Telescope
National Facility and the University of Manchester’s Jodrell Bank Observatory,
funded by the Particle Physics and Astronomy Research Council.

The receiver gives the telescope 13 beams capable of scanning the sky
simultaneously and, as Professor Andrew Lyne of the University of Manchester
explained, "It’s like having over a dozen giant radio telescopes operating at
once". As a result, the system requires 13 sets of sophisticated data
acquisition systems, one for each beam, which were largely developed and built
by the UK group. Following initial detection at Parkes, confirmation and
follow-up observations for many of the new pulsars are made with the 76-metre
Lovell Radio Telescope at Jodrell Bank. The main processing of the survey in
which the PSR J0737-3039 system was discovered was conducted on a cluster of
computers at Cagliari Astronomical Observatory.

Images and Animations

More images and animations representing this system can be found at

[Image and animation 1:

* Web Images (JPG, ~40KB)

* Broadcast Images (TIFF, broadcast quality)

* Web (MPEG2 320×256, 5MB)
* PAL (MPEG2, 29MB)
* NTSC (MPEG2, 24MB)

Formation of the double pulsar system. The first-formed pulsar is ‘spun up’ to
become a rapidly rotating ‘millisecond pulsar’ by matter accreting from its red
giant companion.

Evolution animation: How the double pulsar system formed. The double pulsar
probably formed from a pair of massive stars orbiting each other. (This
animation does not show the orbital motion.) The more massive star ended its
life first, swelling to become a red giant and then exploding as a supernova,
its core forming a pulsar. The second star entered the red giant phase later:
when it did, matter from this star was transferred onto its pulsar companion,
spinning that up to become a fast-rotating "millisecond" pulsar. The red giant
then went supernova, forming the second, slower, pulsar.

Animation: John Rowe Animation

[Image and animation 2:

* Web Images (JPG, ~40KB)

* Broadcast Images (TIFF, broadcast quality)

* Web (MPEG2 320×256, 3MB)

* PAL (MPEG2, 20MB)

* NTSC (MPEG2, 17MB)]

Current state of the double pulsar system.

Animation: John Rowe Animation