PSR B1257+12

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PSR B1257+12
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PSR B1257+12 Observation data
Epoch J2000.0
Constellation Virgo
Right ascension 13h00m01s
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 to PSR 1257+12) is a pulsar located 980 light-years from Sol.

As of 2007, three extrasolar planets have been discovered orbiting it. The first two were the first extrasolar planets ever discovered.
Contents
[hide]

* 1 Pulsar
* 2 Planets
o 2.1 PSR B1257+12 A
o 2.2 PSR B1257+12 B
o 2.3 PSR B1257+12 C
o 2.4 Possible comet
o 2.5 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] Planets

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

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. If they are the remains of planets orbiting the star before supernova, they were theoretically gas giants with large rocky cores, whose atmospheres were stripped away by the supernova, and which spiralled inward to their current orbits.

It should be noted that the planets of PSR B1275+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.
Companion
(In order from star) ↓ Mass
(MJ) ↓ Orbital period
(days) ↓ Semimajor axis
(AU) ↓ Eccentricity ↓
A 0.000063 ± 0.000006 25.262 ± 0.003 0.19 0
B 0.014 ±0.0006 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
comet <0.000001 ~1300 ~2.6 ?

[edit] PSR B1257+12 A
PSR B1257+12 A
Orbital elements
Semi-major axis a: 0.19 AU
Eccentricity e: 0
Orbital period P: 25.262 ± 0.003 d
Inclination i: ?°
Angular distance θ: 0.633 mas
Longitude of
periastron ω: 0°
Time of periastron τ: 2,449,765.6 ± 0.2 JD
Semi-Amplitude K: ? m/s
Physical characteristics
Mass: 0.020 ± 0.002 ME
Radius: ? RJ
Density: ? kg/m³
Gravity: ? g
Temperature: ? K
Discovery
Discovery date: 1994
Discovery location:
Detection method(s): Pulsar Timing
Discoverer(s): A. Wolszczan
Other catalogue

PSR B1257+12 A is the innermost planet orbiting the pulsar at a distance of 0.19 AU with an orbital period of approximately 25 days. In 1997, it was claimed that this planet was in fact an artifact caused by solar wind, but this claim has since been disproved. It is about twice as massive as Earth's Moon.

[edit] PSR B1257+12 B
PSR B1257+12 B
Orbital elements
Semi-major axis a: 0.36 AU
Eccentricity e: 0.0186 ± 0.0002
Orbital period P: 66.5419 ± 0.0001 d
Inclination i: 53 ± 4°
Angular distance θ: 1.2 mas
Longitude of
periastron ω: 250.4 ± 0.6°
Time of periastron τ: 2,449,768.1 ± 0.1 JD
Semi-Amplitude K: ? m/s
Physical characteristics
Mass: 4.3 ± 0.2 ME
Radius: ? RJ
Density: ? kg/m³
Gravity: ? g
Temperature: ? K
Discovery
Discovery date: 1992
Discovery location:
Detection method(s): Pulsar Timing
Discoverer(s): A. Wolszczan
Other catalogue

PSR B1257+12 B is the second planet orbiting the pulsar at a distance of 0.36 AU with an orbital period of approximately 66 days. The planet is over four times as massive as the Earth. Because planet B and planet C orbit rather close to each other, they cause measurable perturbations in each other's orbits. As expected, perturbations were detected confirming that the planets are real. Accurate masses of the two planets, as well as their inclinations, were measured by calculating how much the planets interfere each other.

[edit] PSR B1257+12 C
PSR B1257+12 C
Orbital elements
Semi-major axis a: 0.46 AU
Eccentricity e: 0.0252 ± 0.0002
Orbital period P: 98.2114 ± 0.0002 d
Inclination i: 47 ± 3°
Angular distance θ: 1.533 mas
Longitude of
periastron ω: 108.3 ± 0.5°
Time of periastron τ: 2,449,766.5 ± 0.1 JD
Semi-Amplitude K: ? m/s
Physical characteristics
Mass: 3.9 ± 0.2 ME
Radius: ? RJ
Density: ? kg/m³
Gravity: ? g
Temperature: ? K
Discovery
Discovery date: 1992
Discovery location:
Detection method(s): Pulsar Timing
Discoverer(s): A. Wolszczan
Other catalogue

PSR B1257+12 C is the third planet orbiting the pulsar at an average orbital distance of 0.46 AU with an orbital period of approximately 98 days. It is nearly four times as massive as the Earth.

[edit] Possible 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 ME
Radius: ? RJ
Density: ? kg/m³
Gravity: ? g
Temperature: ? K
Discovery
Discovery date: 2002
Discovery location:
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. It has an upper mass limit of 0.2 Plutos (0.0004 Earths) and a maximum diameter of 1000 km. However, this object is not yet confirmed. This object is sometimes referred to as PSR B1257+12 D[citation needed].

[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. As the fourth planet in the system it was designated PSR B1257+12 D. However, the discovery was not conclusive and was later retracted. It is now thought that the signal came from an asteroidal or cometary body.

[edit] See also

* 51 Pegasi
* PSR B1620-26

[edit] References

1. Wolszczan, A., Frail, D. (1992). "A planetary system around the millisecond pulsar PSR1257 + 12". Nature 355: 145 – 147.
2. Wolszczan, A. (1994). "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR B1257+12". Science 264 (5158): 538 – 542.
3. Konacki, M., Wolszczan, A. (2003). "Masses and Orbital Inclinations of Planets in the PSR B1257+12 System". The Astrophysical Journal 591 (2): L147 – L150.
4. Wolszczan, A. et al. (2000). "Timing Observations of Four Millisecond Pulsars with the Arecibo and Effelsberg Radio Telescopes". The Astrophysical Journal 528 (2): 907 – 912.
5. Salter, C. (2001). "Radio Astronomy Highlights" (PDF). Arecibo Newsletter (33).
6. Daniel Fischer (2002). "A comet orbiting a pulsar?". The Cosmic Mirror (244).
7. Pennsylvania State University (2005). Scientists announce smallest extra-solar planet yet discovered. Press release.

[edit] External links

* Pulsar Planets
* Extrasolar Planets Encyclopaedia: PSR 1257+12
* Extrasolar Visions: PSR 1257+12
* SPACE.com: Earth-Sized Planets Confirmed, But They're Dead Worlds

Retrieved from "http://en.wikipedia.org/wiki/PSR_B1257%2B12"

Categories: All articles with unsourced statements | Articles with unsourced statements since February 2007 | Millisecond pulsars | Extrasolar planets | Science and technology in Poland | Virgo constellation | Hypothetical extrasolar planets
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