Pulsar Pair Gives Scientists Magneto-Pause for Thought
A study of the first double-pulsar binary system to be discovered shows that
magnetic interactions between the pulsars are strikingly similar to those
between the Sun and the Earth.
Radiation and particles emitted from one pulsar appear to have a similar
warping effect on the magnetic bubble surrounding its companion star as the
solar wind has on the Earth’s magnetosphere.
The pulsar pair was discovered in 2003 by an international team of
scientists, including astronomers from Jodrell Bank Observatory, working at
the Parkes Radio Telescope in Australia. Several other binary systems
containing a pulsar and a neutron star have been identified but the pair of
pulsars, PSRs J0737-3039A and B, is the only example where both co-orbiting
objects show the regular flash of a pulsar signal. Since the discovery,
astronomers have been observing the pulsars as they orbit one another
separated by less than a million kilometres, a distance smaller than the
diameter of the Sun. Writing in February’s Astronomy & Geophysics Magazine,
Francis Graham-Smith and Maura Ann McLaughlin show how studies of the pulsar
pair have dramatically improved our understanding of pulsars and neutron
stars, as well as interactions between charged particles and magnetic
fields.
The two pulsars have different rotational periods: pulsar A rotates 44 times
each second whereas pulsar B takes 2.8 seconds to spin once on its axis.
Each pulsar’s signature flash-rate allows astronomers to track them both
during their orbit and deduce information about their magnetic environment.
Each pulsar is only about ten kilometres across but is surrounded by a
magnetosphere that is thousands of kilometres in diameter. Because we view
the orbit nearly edge-on, once per orbit pulsar A is eclipsed as it passes
behind pulsar B. Pulsar B’s magnetosphere is over 100 times larger than that
of pulsar A and this should mean that it blocks sight of pulsar A’s
radiation flashes for several minutes during each orbit. However, initial
observations showed that the eclipse lasted for just 30 seconds, indicating
that B’s magnetosphere has a much smaller diameter than expected.
Observations show that there is a distinct boundary, or magnetopause,
surrounding pulsar B’s magnetosphere. Just as the solar wind warps the
Earth’s magnetosphere as it sweeps past, a wind emitted from pulsar A
appears to be constricting the magnetosphere of pulsar B, compressing it
into a comet-like tail that streams radially outwards.
By contrast, pulsar A’s magnetosphere is much smaller and appears to be
unaffected by its proximity to pulsar B. Previous observations of single
pulsars have shown the existence of pulsar winds, but the double-pulsar
binary system gives the first opportunity to study a stream close to its
source. Contrasting the interactions of the wind in the pulsar system with
those of the solar wind in the terrestrial system, where the magnetic fields
are more than three orders of magnitude smaller, should assist plasma
physicists in understanding large and small-scale processes.
The pulsar pair has already been used to demonstrate the effects of Einstein’s
theory of General Relativity and was ranked by the journal “Science” as
the sixth most important scientific breakthrough in 2004.
FURTHER INFORMATION
The full text of the article and accompanying images can be found at:
http://www.ras.org.uk/html/press/pn0502ras_information.html
More details of the remarkable interactions between the two pulsars can be
found in McLaughlin et al. (Astrophysical Journal, 2004, 613, L57) and
McLaughlin et al. (Astrophysical Journal, 2004, 616, L131).
Jodrell Bank Observatory’s press pages:
http://www.jb.man.ac.uk/news/doublepulsar2/
NOTES FOR EDITORS
The Royal Astronomical Society is the UK’s leading professional body for
astronomy & astrophysics, geophysics, solar and solar-terrestrial physics,
and planetary sciences. The Society publishes two specialist scientific
publications, Monthly Notices of the RAS and Geophysical Journal
International, together with a full-colour journal of news and reviews,
Astronomy & Geophysics.
Pulsars
Pulsars are spinning neutron stars — the dense remnants of large stars that
have run out of fuel and blown off their outer layers in supernova
explosions. Jets of charged particles stream from their poles, generating
bright beams of electromagnetic radiation. The rotational axis and magnetic
field axis of pulsars are not aligned, so the radiation beams emitted from
the poles appear to sweep round like a lighthouse’s flash.
Double Pulsar Binary System PSRs J0737-3039A and B
Pulsars J0737-3039A and B were discovered by an international team of
scientists, including astronomers from Jodrell Bank Observatory UK. Pulsar A
was discovered in April 2003 using the Parkes radiotelescope in Australia
(Burgay et al. Nature, 2003, 426, 531). Pulsar B was discovered in October
2003 during a test of a new technique to search for fast binary pulsars
(Lyne et al. Science, 2004, 303, 1153).
The Solar Wind
The solar wind is a stream of electrically charged particles that is emitted
in all directions from the Sun’s outermost layers. The solar wind distorts
the shape of the Earth’s magnetic field, compressing it on the sunward side
and pushing it into a long tail on the far side. Earth’s magnetic field
shields the planet from the bulk of the solar wind, which would otherwise
strip away our atmosphere.
CONTACTS
Professor Francis Graham-Smith
Jodrell Bank Observatory
University of Manchester, Macclesfield, Cheshire, SK11 9DL, UK
Tel: +44 (0) 1477-572240
E-mail: fgs@jb.man.ac.uk
Dr Maura Ann McLaughlin
Jodrell Bank Observatory
University of Manchester, Macclesfield, Cheshire, SK11 9DL, UK
Tel: +44 (0) 1477-572672
E-mail: mclaughl@jb.man.ac.uk
Astronomy & Geophysics
Dr Sue Bowler (Editor)
Tel: +44 (0) 113 343 6672
E-mail: phy6sb@phys-irc.leeds.ac.uk
