December 9, 2003
Neutron
Stars May Merge More Often Than Thought
EVANSTON, Ill.
--- A recent discovery of a double neutron-star system has helped
to increase astronomers’ chances at collecting
the information they need to better understand the black holes
and neutron stars in our Galaxy.
Neutron star pairs may merge and give off a burst of gravitational
waves about six times more often than previously thought, scientists
report in the Dec. 4 issue of the journal Nature. If so, the current
generation of gravitational-wave detectors might be able to register
such an event every year or two, rather than about once a decade
-- the most optimistic prediction until now.
Gravitational
waves were predicted by Einstein’s general
theory of relativity. Astronomers have indirect evidence of their
existence but have not yet detected them directly.
The revised estimate of the neutron-star merger rate springs
from the discovery of a double neutron-star system, a pulsar called
PSR J0737-3039 and its neutron-star companion, by a team of scientists
from Italy, Australia, the United Kingdom and the United States
using the 64-m CSIRO Parkes radio telescope in eastern Australia.
Vicky Kalogera, assistant professor of physics and astronomy
at Northwestern University, is a member of the international team.
She, along with her graduate student Chunglee Kim and colleague
Duncan Lorimer from the University of Manchester, used the characteristics
of the newly discovered pair of neutron stars to calculate how
many more such pairs exist in our Galaxy. Next, they calculated
that first-generation gravitational wave detectors, like LIGO in
the United States, should be able to detect the merger of neutron
stars once every year and a half.
“We know gravitational waves exist, but only from indirect
evidence,” said Kalogera. “Once we can detect the gravitational
waves from these merger events directly, we will have an amazing
new window into the cosmos. We will learn a great deal more about
relativity and the properties of astronomical objects such as neutron
stars and black holes.”
Marta Burgay,
a Ph.D. student at the University of Bologna in Italy is lead
author on the Nature paper. Kalogera’s portion
of the research was supported by the National Science Foundation’s
gravitational physics program and the David and Lucile Packard
Foundation. |