Nature's Most Precise Clocks May Make "Galactic GPS" Possible; Pulsing Pulsars Help in Search for Gravitational Waves

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WASHINGTON -- Radio astronomers have uncovered 17 millisecond pulsars
in our galaxy by studying unknown high-energy sources detected by
NASA's Fermi Gamma-ray Space Telescope. The astronomers made the
discovery in less than three months. Such a jump in the pace of
locating these hard-to-find objects holds the promise of using them
as a kind of "galactic GPS" to detect gravitational waves passing
near Earth.

A pulsar is the rapidly spinning and highly magnetized core left
behind when a massive star explodes. Because only rotation powers
their intense gamma-ray, radio and particle emissions, pulsars
gradually slow as they age. But the oldest pulsars spin hundreds of
times per second -- faster than a kitchen blender. These millisecond
pulsars have been spun up and rejuvenated by accreting matter from a
companion star.

"Radio astronomers discovered the first millisecond pulsar 28 years
ago," said Paul Ray at the Naval Research Laboratory in Washington.
"Locating them with all-sky radio surveys requires immense time and
effort, and we've only found a total of about 60 in the disk of our
galaxy since then. Fermi points us to specific targets. It's like
having a treasure map."

Millisecond pulsars are nature's most precise clocks, with long-term,
sub-microsecond stability that rivals human-made atomic clocks.
Precise monitoring of timing changes in an all-sky array of
millisecond pulsars may allow the first direct detection of
gravitational waves -- a long-sought consequence of Einstein's
relativity theory.

"The Global Positioning System uses time-delay measurements among
satellite clocks to determine where you are on Earth," explained
Scott Ransom of the National Radio Astronomy Observatory in
Charlottesville, Va. "Similarly, by monitoring timing changes in a
constellation of suitable millisecond pulsars spread all over the
sky, we may be able to detect the cumulative background of passing
gravitational waves."

The sources Fermi detected are not associated with any known gamma-ray
emitting objects and did not show evidence of pulsing behavior.
However, scientists considered it likely that many of the
unidentified sources would turn out to be pulsars.

For a more detailed look at radio wavelengths, Ray organized the Fermi
Pulsar Search Consortium and recruited a handful of radio astronomers
with expertise in using five of the world's largest radio telescopes
-- the National Radio Astronomy Observatory, Robert C. Byrd Green
Bank Telescope in W.Va., the Parkes Observatory in Australia, the
Nancay Radio Telescope in France, the Effelsberg Radio Telescope in
Germany and the Arecibo Telescope in Puerto Rico.

After studying approximately 100 targets, and with a computationally
intensive data analysis still under way, the discoveries have started
to pour in.

"Other surveys took a decade to find as many of these pulsars as we
have," said Ransom, who led one of the discovery groups. "Having
Fermi tell us where to look is a huge advantage."

Four of the new objects are "black widow" pulsars, so called because
radiation from the recycled pulsar is destroying the companion star
that helped spin it up.

"Some of these stars are whittled down to masses equivalent to tens of
Jupiters," said Ray. "We've doubled the known number of these systems
in the galaxy's disk, and that will help us better understand how
they evolve."

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle
physics partnership, developed in collaboration with the Department
of Energy, along with important contributions from academic
institutions and partners in France, Germany, Italy, Japan, Sweden,
and the U.S. The National Radio Astronomy Observatory is a facility
of the National Science Foundation operated under cooperative
agreement by Associated Universities, Inc.

For images and animations related to this release, visit:

http://www.nasa.gov/fermi

Source: NASA