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Concept
Planète de pulsar
Résumé
Pulsar planets are planets that are found orbiting pulsars, or rapidly rotating neutron stars. The first such planets to be discovered were around a millisecond pulsar in 1992 and were the first extrasolar planets to be confirmed as discovered. Pulsars are extremely precise clocks and even small planets can create detectable variations in pulsar traits; the smallest known exoplanet is a pulsar planet.
They are extremely rare, with only half a dozen listed by the NASA Exoplanet Archive. Only special processes can give rise to planet-sized companions around pulsars, and many are thought to be exotic bodies such as planets made of diamond that were formed through the partial destruction of a companion star. The intense radiation and winds consisting of electrons-positrons would tend to strip atmospheres away from such planets, thus making them unlikely abodes for life.
It is thought that the formation of planets requires the existence of a protoplanetary disk with a "dead zone" where there is no turbulence. There, planetesimals can form and accumulate without falling into the star. Compared to young stars, neutron stars have a much higher luminosity and thus the formation of a dead zone is hindered by the ionization of the disk by the neutron star's radiation, which allows the magnetorotational instability to trigger turbulence and thus destroy the dead zone. Thus, a disk needs to have a large mass if it is to give rise to planets.
There are several processes that could give rise to planetary systems:
"First generation" planets are planets that orbited the star before it went supernova and became a neutron star: Massive stars tend to lack planets, possibly due to the difficulty in detecting them around very bright stars but also because the radiation from such stars would destroy the protoplanetary disks. Planet within about 4 astronomical units distance from the star risk being engulfed and destroyed when it becomes a red giant/red supergiant.
Source officielle
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