PSR B1257+12

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PSR B1257+12

Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Virgo
Right ascension 13h00m01s
Declination +12° 40' 57"
Spectral type neutron star
Variable type Pulsar
Mass assumed 1.5 M
Radius ~0.00002 R
Rotation 0.006219 s
Age 3 [1] Gyr
Other designations
PSR J1300+1240 , PSR B1257+12 , PSR 1257+12 , PSR 1300+1240

PSR B1257+12 (PSR 1257+12) is a pulsar located 1000 light years from the Sun. In 1992, two planets were discovered orbiting the pulsar, and a third was confirmed in 1994.


PSR B1257+12 is in the constellation of Virgo. The designation PSR B1257+12 refers to its coordinates in the B1950.0 epoch and it being a pulsar.

PSR B1257+12 was discovered by the Polish astronomer Aleksander Wolszczan on February 9, 1990 using the Arecibo radio telescope. It is a millisecond pulsar, a kind of neutron star, and was found to have anomalies in the pulsation period, which led to investigations as to the cause of the irregular pulses. In 1992 Wolszczan and Dale Frail published a famous paper on the first confirmed discovery of planets outside our solar system. Using refined methods one more planet was found orbiting this pulsar in 1994. The discovery stimulated a search for planets orbiting other pulsars, but it turned out such planets are rare; only one other pulsar planet, orbiting PSR B1620-26, has been confirmed. PSR B1257+12 has a rotation period of 6.22 milliseconds (9,650 rpm).

Planetary system[edit]

The PSR B1257+12 planetary system[1]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
A (b) 0.020 ± 0.002 M 0.19 25.262 ± 0.003 0.0 ~50°
B (c) 4.3 ± 0.2 M 0.36 66.5419 ± 0.0001 0.0186 ± 0.0002 53°
C (d) 3.9 ± 0.2 M 0.46 98.2114 ± 0.0002 0.0252 ± 0.0002 47°


Artist's impression of the planets orbiting PSR B1257+12.

In 1992, Aleksander Wolszczan and Dale Frail discovered that the pulsar had two planets. These were the first discovery of extrasolar planets to be confirmed;[2][3] as pulsar planets, they surprised many astronomers who expected to find planets only around main-sequence stars. Additional uncertainty surrounded the system, because of a claim of an earlier pulsar planet around PSR 1829-10 that had to be retracted due to errors in calculations. Later, an additional planet was discovered. Additionally, this system may have an asteroid belt or a Kuiper belt.

The planets are believed to be the result of a second round of planetary system formation[4] resulting from unusual supernova remnants or a quark-nova.[5]

The planets of PSR B1257+12 are designated from A to C (ordered by increasing distance), unlike planets around normal stars which follow the standard where the first discovered planet in the system is b, followed by c and so on. The "A" planet is the lowest mass planet yet discovered by late 2014 by any observational technique, and has somewhat less than twice the mass of Earth's moon.

The planets and their host star is one of the planetary systems selected by the International Astronomical Union as part of their public process for giving proper names to exoplanets and their host star (where no proper name already exists).[6][7] The process involves public nomination and voting for the new names, and the IAU plans to announce the new names in mid-November 2015.[8]

Retracted claim of fourth orbital body[edit]

In 1996, a possible Saturn-like (100 Earth mass) gas giant was announced orbiting the pulsar at a distance of about 40 AU.[9] The original hypothesis was retracted and a reinterpretation of the data led to a new hypothesis of a dwarf planet one-fifth the size of Pluto orbiting PSR B1257+12 at an average orbital distance of 2.4 AU with an orbital period of approximately 4.6 years.[10][11][12] The dwarf planet hypothesis was also retracted because further observations showed that the pulsation anomalies previously thought to reveal a fourth orbital body are "not periodic and can be fully explained in terms of slow changes in the pulsar’s dispersion measure."[12]

See also[edit]


  1. ^ a b 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. ^ "Pulsar Planets". 
  3. ^ Wolszczan, A.; Frail, D. (1992). "A planetary system around the millisecond pulsar PSR1257 + 12". Nature 355 (6356): 145–147. Bibcode:1992Natur.355..145W. doi:10.1038/355145a0. 
  4. ^ Podsiadlowski, P. (1993). "Planet Formation Scenarios". Planets around pulsars; Proceedings of the Conference, California Inst. of Technology, Pasadena, Apr. 30-May 1, 1992: 149–165. Bibcode:1993ASPC...36..149P. 
  5. ^ "Planets orbiting Quark Nova compact remnants". arXiv:astro-ph/0301574. Bibcode:2003A&A...407L..51K. doi:10.1051/0004-6361:20030957. 
  6. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. 9 July 2014
  7. ^ NameExoWorlds.
  8. ^ NameExoWorlds.
  9. ^ Wolszczan, Alex (1997). "The Pulsar Planets Update". Planets Beyond the Solar System and the Next Generation of Space Missions. Proceedings of a workshop held at Space Telescope Science Institute, Baltimore, MD, October 16–18, 1996. ASP Conference Series, Vol. 119. Astronomical Society of the Pacific. p. 135. Bibcode:1997ASPC..119..135W. 
  10. ^ Fischer, Daniel (2002-10-25). "A comet orbiting a pulsar?". The Cosmic Mirror (244). Retrieved 2013-03-02. 
  11. ^ "Smallest extra-solar planet found". BBC News. 2005-02-14. Retrieved 2013-03-02. 
  12. ^ a b Wolszczan, Alex (January 2012). "Discovery of pulsar planets". New Astronomy Reviews (Elsevier) 56 (1): 2–8. Bibcode:2012NewAR..56....2W. doi:10.1016/j.newar.2011.06.002. 

External links[edit]

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