Pulsar planet

Pulsar planets are planets that are found orbiting pulsars, or rapidly rotating neutron stars. The first such planet to be discovered was around a millisecond pulsar and was the first extrasolar planet to be discovered.

Pulsar planets

Pulsar planets are discovered through pulsar timing measurements, to detect anomalies in the pulsation period. Any bodies orbiting the pulsar will cause regular changes in its pulsation. Since pulsars normally rotate at near-constant speed, any changes can easily be detected with the help of precise timing measurements.

In 1991, Andrew G. Lyne announced the first ever extrasolar planet discovered around PSR 1829-10. [ [http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v352/n6333/abs/352311a0.html Nature vol.352 no.6333 : A planet orbiting the neutron star PSR1829–10] ] However, this was later retracted, [ [http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v355/n6357/abs/355213b0.html "Nature" vol.355 no.6357 : No planet orbiting PS R1829–10] ] just before the first real pulsar planets were announced.

In 1992, Aleksander Wolszczan and Dale Frail announced the discovery of a multi-planet planetary system around the millisecond pulsar PSR 1257+12. [ cite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1992Natur.355..145W&db_key=AST&nosetcookie=1|author=Wolszczan, A., Frail, D.|title=A planetary system around the millisecond pulsar PSR1257 + 12|journal=Nature|volume=355|pages=145–147|year=1992|doi=10.1038/355145a0 ] These were the first two extrasolar planets discovered, and thus the first multi-planet extrasolar planetary system discovered, and the first pulsar planets discovered. There was doubt concerning the discovery because of the retraction of the previous pulsar planet, and questions about how pulsars could have planets. Fortunately, the planets proved to be real. [ cite journal|url=http://adsabs.harvard.edu/cgi-bin/bib_query?1994Sci...264..538W|author=Wolszczan, A.|title=Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR B1257+12|journal=Science|volume=264|issue=5158|pages=538–542|year=1994|doi=10.1126/science.264.5158.538|pmid=17732735 ]

In 2000, the millisecond pulsar PSR B1620-26 was found to have a circumbinary planet (PSR B1620-26 b) that orbits both it and its companion white dwarf, WD B1620-26. This was announced as the oldest planet ever discovered, at 12.6 billion years old. [cite web | author=Britt, Robert Roy | title=Primeval Planet: Oldest Known World Conjures Prospect of Ancient Life | work=Space.com | url=http://www.space.com/scienceastronomy/oldest_planet_030710-1.html | accessdate=2007-06-12] It is currently believed to have originally been the planet of WD B1620-26 before becoming a circumbinary planet, and therefore, while discovered through the pulsar timing method, it did not form the way that PSR B1257+12's planets are thought to have.

In 2006, the magnetar 4U 0142+61, located 13,000 light years from Earth, was found to have a circumstellar disk. The discovery was made by a team led by Deepto Chakrabarty of MIT using the Spitzer Space Telescope. [cite web| url=http://www.cnn.com/2006/TECH/space/04/05/supernova.blast.ap/index.html| title= Scientists crack mystery of planet formation| date=April 5, 2006| publisher=CNN.com| accessdate=2006-04-05] The disk is thought to have formed from metal-rich debris left over from the supernova that formed the pulsar roughly 100,000 years ago and is similar to those seen around Sun-like stars, suggesting it may be capable of forming planets in a similar fashion. Pulsar planets would be unlikely to harbour life as we know it, because the high levels of ionizing radiation emitted by the pulsar and the corresponding paucity of visible light.

List of pulsar planets

Confirmed planets

Disproven planets

ee also

* List of stars with confirmed extrasolar planets
* List of unconfirmed exoplanets
* List of stars with proplyds
* Extrasolar planet
* Andrew Lyne
* Aleksander Wolszczan
* Dale Frail

References