PSR B1257+12

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**PSR B1257+12**
Observation data Epoch J2000.0
Constellation (pronunciation)	Virgo
Right ascension	13^h00^m01^s
Declination	+12° 40' 57"
Apparent magnitude (V)	?
Characteristics
Spectral type	?
U-B color index	?
B-V color index	?
Variable type	Pulsar
Details
Mass	assumed 1.4 M_☉
Radius	~0.00002 R_☉
Luminosity	? L_☉
Temperature	? K
Metallicity	?
Rotation	0.006219 s
Age	800 million years
Other designations
PSR J1300+1240

PSR B1257+12, sometimes abbreviated as PSR 1257+12, is a pulsar located 980 light-years from the Sun. As of 2007, it is confirmed that three extrasolar planets orbit the pulsar (the first two were the first extrasolar planets ever discovered).

1 Pulsar
2 Planetary system
- 2.1 Suspected Comet
- 2.2 Disproven Gas Giant
3 See also
4 References
5 External links

[edit] Pulsar

PSR B1257+12 is in the constellation of Virgo. The designation PSR B1257+12 refers to its coordinates in the B1950.0 epoch. It is located at about 980 light years from Earth.

PSR B1257+12 was discovered by the Polish astronomer Aleksander Wolszczan in 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. It has a rotation period of 6.22 milliseconds (9,646.3rpm).

[edit] Planetary system

The PSR B1257+12 system
Planet (in order from star)	Mass (M_J)	Orbital period (days)	Semimajor axis (AU)	Eccentricity
A	7e−05	25.262 (± 0.003)	0.19	0.00
B	0.013	66.5419 (± 0.0001)	0.36	0.0186 (± 0.0002)
C	0.012 (± 0.0006)	98.2114 (± 0.0002)	0.46	0.0252 (± 0.0002)

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

In 1992, Aleksander Wolszczan and Dale Frail discovered that the pulsar has two planets. These were the first extrasolar planets ever discovered ^[1]; as pulsar planets, they surprised many astronomers who expected to find planets only around main sequence stars. Additional uncertainty surrounded the system, because 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.

Size comparison of the three pulsar planets and the Earth. The letters represent their position from the pulsar (not the name of the planet).

The planets are believed to either be the rocky cores of former gas giants, or the result of a second round of planetary system formation resulting from unusual supernova remnants. It should be noted that the planets of PSR B1257+12 are designated from A to D (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.

Planets of PSR B1257+12

[edit] Suspected Comet

**PSR B1257+12 comet**
Orbital elements

Semi-major axis a:	~2.6 AU
Eccentricity e:	?
Orbital period P:	~3.5 y
Inclination i:	?°
Angular distance θ:	8.665 mas
Longitude of periastron ω:	?°
Time of periastron τ:	? JD
Semi-amplitude K:	? m/s
Physical characteristics
Mass:	<0.0004 M_E
Radius:	? R_J
Density:	? kg/m³
Gravity:	? g
Temperature:	? K
Discovery
Discovery date:	2002
Discovery site:	Poland
Detection method(s):	Pulsar Timing
Discoverer(s):	A. Wolszczan
Other catalogue

It is suspected that an asteroid or comet is orbiting PSR B1257+12 at an average orbital distance of 2.6 AU with an orbital period of approximately 3.5 years. The object is so small that it is not even considered to be a planet, but it is the first known extrasolar asteroid or comet akin to the objects in the Kuiper belt in our solar system. It is possible that this object is the largest member of a belt of minor objects around the pulsar.

[edit] Disproven Gas Giant

In 1996, a possible Saturn-like (100 Earth mass) gas giant was announced orbiting the pulsar at a distance of about 40 AU. However, the discovery was not conclusive and was later retracted. It is now thought that the signal came from an asteroidal or cometary body.