Nature's Most Precise Clocks May Make "Galactic GPS" PossibleThere are unidentified flying objects out in space. Or at least objects whizzing through the Universe that we don't immediately recognize. The image above shows some of them - or at least it did. This image is the map of the Gamma-ray Universe obtained (and being obtained still) by the Fermi Gamma-ray Space Telescope. Fermi, as it's affectionately known (or FGRST, somewhat less affectionately) scans the sky and creates a new map of the entire Universe every few hours. It detects Gamma-ray emission from active galaxies (mostly), supernova remnants, starbursts; more than a 1000 objects so far. Many of the sources are mysterious, with no known counterparts at other wavelengths. Collaborations of astronomers are working hard to determine what these unknown sources are. The Fermi Pulsar Search Consortium is a group of radio astronomers dedicated to see if any of the detected Fermi sources are pulsars (neutron stars spinning rapidly in their graves) by looking for high frequency periodic signals from these GR sources. This effort has successfully shown that the 17 Fermi sources (circled above) are millisecond pulsars, extreme neutron stars rotating about 100 times or more per second. These strange, rare objects are old and have been spun up, probably by devouring a companion star over the course of a few billion years. Millisecond pulsars are precise natural clocks and are of special astrophysical interest. Continued study of these objects may lead to the discovery of another long-sought GR source: gravitational radiation.
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