January 4, 2002
Newly Commissioned Green Bank Telescope bags new pulsars
Astronomers using the National Science Foundation's newly commissioned
Robert C. Byrd Green Bank Telescope (GBT) have discovered a windfall of
three previously undetected millisecond pulsars in a dense cluster of
stars in the Milky Way Galaxy.
"This globular cluster, known as
Messier 62 ,
has been very well studied,
and it would have been an exciting discovery to find just one new
pulsar. The fact that we were able to detect three new pulsars at one
time is simply remarkable," said Bryan Jacoby, a graduate student at the
California Institute of Technology who led the research team. Results
of the discovery were recently announced in an International
Astronomical Union Circular
( No. 7783 ).
Jacoby and his colleague Adam Chandler, also a graduate student at
Caltech, used the GBT to search for three 3 previously known pulsars in
this cluster. Their research was part of the GBT's Early Science
Program, which allows scientific investigations during the testing and
commissioning of the telescope. To record their data, the researchers
used the Berkeley-Caltech Pulsar Machine, a new instrument whose
development was overseen by Donald Backer at the University of
California at Berkeley.
After their data were analyzed, the researchers discovered the telltale
signatures of three additional pulsars and their white dwarf companion
Pulsars, which act as "lighthouses" in the Galaxy, are rapidly
rotating neutron stars that emit intense beams of radio waves along their
misaligned magnetic axes. When these beams intersect the Earth, we see the
pulsar flash on and off. Due to their exquisitely steady rotation, pulsars
allow astronomers to study the basic laws of physics and the ways in
which these dense clusters and exotic stellar systems are formed.
Astronomers study globular clusters because they are among the oldest
building blocks of our Galaxy. With their very dense stellar
populations, these clusters are breeding grounds for unusual binary star
systems, like the ones detected by the researchers.
All three pulsars are known as "millisecond pulsars" because they make
one complete rotational spin in only a few thousandths of a second. One
of these newly discovered pulsars spins at approximately 440 rotations
per second, and the other two both spin about 300 times per second. All
are orbited by white dwarf stars with orbital periods ranging from 4 to 27
"This discovery demonstrates the remarkable sensitivity of the Green
Bank Telescope," said Phil Jewell, site director for the National Radio
Astronomy Observatory in Green Bank, W.Va. "The fact that these pulsars
were never before detected in this highly studied area of the Galaxy
shows that the GBT has outstanding capabilities and will be an important
tool for astronomers to make very precise, very sensitive observations
of the Universe.
The GBT is the world's largest fully steerable radio telescope. It was
dedicated on August 25, 2000, after nearly 10 years of construction.
Since that time, engineers and scientists at the NRAO in Green Bank have
been testing the telescope and outfitting it with the sensitive
receivers and electronics that will make it one of the world's premier
"As a graduate student," said Jacoby "this discovery was particularly
satisfying, and I feel privileged to be part of the history of the Green
Shrinivas Kulkarni, the Caltech faculty advisor for this project,
remarked, "it is very satisfying to see such discoveries being made by
young people. GBT is poised to play a significant role in the education
of young astronomers."
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement with Associated