WASHINGTON ? A newly discovered trove of strange spinning stars in our galaxy could help find evidence for Einstein's prediction of gravitational waves.
The peculiar stars are very dense, strongly magnetic stars called millisecond pulsars, which rotate hundreds of times per second ? faster than a kitchen blender. Seventeen of these objects were recently identified with help from NASA's Fermi space telescope, which scans the skies in high-energy gamma-ray light.
The findings were presented Tuesday at the 215th meeting of the American Astronomical Society in Washington, D.C.
Pulsars are created when massive stars die and collapse in supernova explosions into compact objects made only of neutrons. When roughly the sun's mass is packed into a tiny space about the size of a city, the conserved angular momentum causes the resulting neutron star to spin very rapidly, and to emit a ray of light that sweeps around like a lighthouse beam.
If the pulsar is aligned with Earth, the light beam will cross our planet once every rotation, creating a pulse of light visible at a regular interval of a few milliseconds or seconds, depending on the pulsar's mass. In fact, pulsars are nature's most precise clocks.
Scientists hope that by monitoring the pulse rate of a large network of pulsars over an extended time, they can create a kind of galactic GPS to find evidence for long-sought gravitational waves.
Gravitational waves are theorized fluctuations in the curvature of space-time predicted by Einstein's theory of general relativity. These waves should propagate through space, transporting energy known as gravitational radiation. And gravitational waves could show up as a kind of correlated wiggle in a network of pulsar clocks.
"The Global Positioning System uses time-delay measurements among satellite clocks to determine where you are on Earth," said researcher 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," said researcher Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va.
The detection of the new objects could greatly aid the search, since millisecond pulsars are relatively difficult to detect ? only about 60 total had been found in the Milky Way before now. Because pulsars shine brightly in gamma-ray light, among other wavelengths, Fermi was able to map a bevy of possible pulsar sources that astronomers then verified with other telescopes.
"Fermi points us to specific targets," said Paul Ray of the Naval Research Laboratory in Washington, D.C. "It's like having a treasure map."
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