PSR B1257+12 A

PSR B1257+12A

Extrasolar planet		List of extrasolar planets
Size comparison of PSR B1257+12 A with Earth. (Based on selected hypothetical modeled compositions)
Parent star
Star		PSR B1257+12
Constellation		Virgo
Right ascension	(α)	13h 00m 01s
Declination	(δ)	+12° 40′ 57″
Distance		980 ly (300 pc)
Spectral type		Pulsar
Mass	(m)	assumed 1.4 M☉
Radius	(r)	~0.00002 R☉
Age		0.8 Gyr
Orbital elements
Semimajor axis	(a)	0.19[1] AU
Eccentricity	(e)	0.0[1]
Orbital period	(P)	25.262 ± 0.003[1] d
Inclination	(i)	50[1][note 1]°
Time of periastron	(T0)	2,449,765.6 ± 0.2[1] JD
Physical characteristics
Mass	(m)	0.020 ± 0.002[1][note 1] M⊕
Discovery information
Discovery date		22 April 1994
Discoverer(s)		Aleksander Wolszczan
Detection method		Pulsar Timing
Discovery site		Poland
Discovery status		Published
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		data

PSR B1257+12A is an extrasolar planet approximately 980 light-years away in the constellation of Virgo. The planet is the innermost object orbiting the pulsar PSR B1257+12, i.e. a pulsar planet. It is about twice as massive as Earth's Moon, and is the least massive planet currently known, including the planets in our solar system.

Name

Artist's impression of PSR B1257+12 A planet.

The planets of PSR B1257+12 are designated from A to D (ordered by increasing distance). The reason that these planets are not named the same as other extrasolar planets is mainly because of time. Being the first ever extrasolar planets discovered, and being discovered around a pulsar, the planets were given the uppercase letters "B" and "C" (like other planets). When a third planet was discovered around the system (in a closer orbit then the other two), the name "A" was commonly used. The extrasolar planet name 51 Pegasi b (the first planet found around a Sun-like star), was the idea used for naming planets. Although these pulsar planets were not renamed, some have done it themselves. PSR B1257+12A is catalogued as "PSR 1257+12b" on The Extrasolar Planets Encyclopaedia.

Notes

1. ^ ^{a b} The value of the inclination is assumed to be 50° based on the inclinations of the other two planets in the system, which have inclinations of 53° and 47° respectively. The quoted mass value is based on this assumed inclination.

References

• Wolszczan, A. (1994). "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR B1257+12" (pdf). Science 264 (5158): 538–542. Bibcode 1994Sci...264..538W. doi:10.1126/science.264.5158.538. PMID 17732735. http://www.astro.psu.edu/~niel/astro550/week07-wolszczan-pulsar-planets.pdf. 

External links

Media related to PSR B1257+12 A at Wikimedia Commons

• extrasolar.net data
• Pulsar Planets

v t e The PSR B1257+12 system Stars PSR B1257+12 Planets PSR B1257+12 A PSR B1257+12 B PSR B1257+12 C PSR B1257+12 D

Coordinates: 13^h 00^m 01^s, +12° 40′ 57″

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