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Lich c, PSR B1257+12 c, PSR B1257+12 B

Proper NamePoltergeist
DesignationsPSR B1257+12 c, PSR B1257+12 B
ClassificationSuper Earth
Orbital Period66 days, 13 hours
Mean Distance from Lich53.9 million km
0.36 AU
Mass4.292 x Earth
DiameterNot known
TemperatureNot known
Parent objectLich (PSR B1257+12), pulsar in Virgo
Other planets in this systemDraugr (Lich b), Earth-mass planet
Phobetor (Lich d), Super Earth

One of three known planets that pursue close orbits around the pulsar PSR B1257+12, commonly known as 'Lich', more than two thousand light years from the Solar System in the constellation of Virgo. Poltergeist is important in the history of extrasolar planet exploration as one of the first pair of planets to be discovered in orbit around any body beyond the Solar System, in the year 1992. (The other planet of the pair was Phobetor in orbit around the same pulsar, with another small planet, Draugr, being discovered two years later.)

All three known planets of the system pursue close orbits around the central pulsar, with even the most distant of the three, Phobetor, orbiting at distance less than half that of Earth's distance from the Sun. Poltergeist is the second planet of the three, with an orbital distance a tenth of an AU closer to Lich than Phobetor's. Lying so close to the pulsar, Poltergeist's year is a short one, and it completes each orbit in a period of just sixty-six days. Physically Poltergeist is rather larger and more massive than Earth; with a mass some four times greater than Earth's, Poltergeist belongs to the class of planets designated 'Super Earths'.

This image shows its location of the Lich pulsar in the sky, to the north of the yellow giant Vindemiatrix in Virgo, though the pulsar and its planets cannot be seen directly. Imagery provided by Aladin sky atlas

As one of the first exoplanets ever discovered, Poltergeist was given its designation at a time before any formal naming conventions for such planets had been established. It was initially given the identifier 'PSR B1257+12 B' ('B' indicating that it was the second of the three planets from the Lich pulsar). Later conventions established that planets should be designated in discovery order, and so it acquired the alternative designation 'PSR B1257+12 c'. Following a public vote, it was also given an official proper name, Poltergeist, in 2015.


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