PSR B1257+12 A
| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
 (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 Maciej Konacki | |
| Discovery method | Pulsar Timing | |
| Discovery site |  United States[2] | |
| Discovery status | Published | |
| Database references | ||
| Extrasolar Planets Encyclopaedia | data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
PSR B1257+12 b (ex PSR B1257+12 A) is an exoplanet (or 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 in the dead stellar system. It is about twice as massive as the Moon, and is listed as the least massive planet known, including among the planets in the Solar System.[2]
Name
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 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 than 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 officially renamed, some have done it themselves. PSR B1257+12 A is catalogued as "PSR 1257+12 b" on The Extrasolar Planets Encyclopaedia.
Notes
- ↑ 1.0 1.1 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
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Konacki, M.; Wolszczan, A. (2003). "Masses and Orbital Inclinations of Planets in the PSR B1257+12 System". The Astrophysical Journal 591 (2): L147–L150. arXiv:astro-ph/0305536. Bibcode:2003ApJ...591L.147K. doi:10.1086/377093.
- ↑ 2.0 2.1 Dumé, Belle (11 February 2005). "Astronomers find smallest exoplanet". PhysicsWeb. Retrieved 20 July 2012.
- 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.
External links
Media related to PSR B1257+12 A at Wikimedia Commons
| Preceded by PSR B1257+12 C |
Least massive exoplanet 1994 — |
Succeeded by |
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Coordinates: 
13h 00m 01s, +12° 40′ 57″