NASA's Fermi Gamma-ray Space Telescope has found a trove of 294 gamma-ray-emitting pulsars, with an additional 34 candidates awaiting confirmation, marking a significant leap in our understanding of these celestial phenomena.
The discovery, part of a catalog produced by an international team of astronomers led by French researchers, is 27 times the number of known pulsars before Fermi's mission in 2008.
The Nature of Gamma-Ray-Emitting Pulsars
The findings offer crucial insights into the diverse nature of pulsars and their potential contributions to various areas of astrophysics research.
Pulsars are highly magnetized rotating neutron stars formed from the remnants of a supernova explosion. They emit beams of energy that sweep through space, resembling the light from a lighthouse.
The new catalog, a collaborative effort involving 170 scientists globally, has compiled comprehensive information on gamma-ray pulsars, opening avenues for further exploration.
David Smith, the study coordinator from the Bordeaux Astrophysics Laboratory in France, emphasized the wide-ranging impact of pulsar research on astrophysics, spanning cosmic rays, stellar evolution, gravitational wave searches, and investigations into dark matter.
"This new catalog compiles full information on all known gamma-ray pulsars in an effort to promote new avenues of exploration," Smith said in a statement.
Fermi's Large Area Telescope, capable of detecting gamma rays with energies billions of times greater than visible light, has played a pivotal role in uncovering the gamma-ray emissions of pulsars.
Unlike most of the 3,400 known pulsars observed through radio waves within the Milky Way galaxy, only about 10% exhibit gamma-ray pulsations. According to NASA, the new catalog significantly expands our knowledge about these high-energy emissions.
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Millisecond Pulsars
The study also sheds light on millisecond pulsars (MSPs), a subset of pulsars with high-speed rotation despite their age. The presence of MSPs in binary systems, where a pulsar is closely paired with a normal star, offers insights into the age-spin paradox, wherein older pulsars surprisingly spin faster.
The intricate dynamics of these systems, often called "Spider" systems, provide valuable clues to the interplay between pulsars and their companions. A notable discovery in the catalog is the black widow pulsar J1555-2908, whose gravitational web may have captured a passing planet.
Examining data from Fermi over a span of 12 years unveiled extended spin variations surpassing those observed in other millisecond pulsars (MSPs).
The inclusion of a planet as a third celestial body in a broad orbit around the pulsar and its companion is regarded as a plausible explanation. Yet, additional observations from Fermi are necessary to affirm this hypothesis.
The study also highlights transitional pulsars like J1023+0038, characterized by erratic gas flows from the companion to the neutron star, leading to the sudden formation of a disk around the pulsar. This disk shines brightly in various spectra, including optical light, X-rays, and gamma rays, altering the detectability of pulses.
"More than 15 years after its launch, Fermi remains an incredible discovery machine, and pulsars and their neutron star kin are leading the way," said Elizabeth Hays, the mission's project scientist at NASA's Goddard Space Flight Center, said in the statement.
The catalog was published in The Astrophysical Journal Supplement.
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