PSR B1620-26

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PSR B1620-26
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PSR B1620−26 A / B

The location of PSR B1620−26 (circled)
Observation data
Epoch J2000.0
Constellation Scorpius (M4)
Right ascension 16h 23m 38s
Declination −26° 31′ 53″
Apparent magnitude (V) +24
Characteristics
Spectral type Pulsar / DB
U-B color index ?
B-V color index ?
Variable type none
Astrometry
Radial velocity (Rv) ? km/s
Proper motion (μ) RA: ? mas/yr
Dec.: ? mas/yr
Parallax (π) ? ± ? mas
Distance 12,400 ly (3,800 pc)
Absolute magnitude (MV) ?
Details
Mass 1.35 / 0.34 M☉
Radius ? R☉
Luminosity ? L☉
Temperature ? K
Metallicity ?
Rotation ?
Age ? / 13000 million years
Other designations
PSR J1623−2631,
16:23:38.22−23:31:53.8 J2000,
16:23:38.24−26:31:53.9,
ICRS 2000

PSR B1620−26 is a binary star about 12,400 light-years away in the globular cluster Messier 4.

It is theorized that originally PSR B1620−26 A had another, lower mass white dwarf companion, which was ejected when the current PSR B1620−26 B interacted with the original binary system. At that time, PSR B1620−26 B was still a main sequence star, with its planet (PSR B1620−26c). Whereupon, the planet settled into orbit around both stars.

The triple system is just outside the core of the globular cluster. The age of the cluster has been estimated to be about 12.7 billion years. Hence this is the age estimate for the birth of the planet, and two stars.

There is a minor dispute about the proper nomenclature rules to use for this unusual star system. One side regards the A/B convention of naming binary stars as having priority, so that the pulsar is PSR B1620-26 A, the white dwarf companion is PSR B1620-26 B and the planet is PSR B1620-26 c. The other side considers PSR to only apply to stars which are pulsars, not their companions, so the white dwarf should be named using the WD convention, making the pulsar PSR B1620-26, the white dwarf WD J1623-266, and the planet PSR B1620-26 b. Early articles used the first convention, but star catalogs have been using the second.[1][2] In practice, context makes it clear whether the pulsar, the white dwarf, the planet, or the system as a whole is being referred to.
Contents
[hide]

* 1 Planet system
* 2 See also
* 3 References
* 4 External links

[edit] Planet system

PSR B1620−26c was originally detected through the Doppler shifts its orbit induces on signals from the star it orbits (in this case, changes in the apparent pulsation period of the pulsar).
The evolution of the PSR B1620−26 system.
The evolution of the PSR B1620−26 system.

In the early 1990s, a group of astronomers led by Donald Backer, studying what they thought was a binary pulsar, determined that a third object was needed to explain the observed Doppler shifts. Within a few years, the gravitational effects of the planet on the orbit of the pulsar and white dwarf had been measured, giving an estimate of the mass of the third object that was too small for it to be a star. The conclusion that the third object was a planet was announced by Stephen Thorsett and his collaborators in 1993.
Companion
(In order from star) Mass
(MJ) Orbital period
(days) Semimajor axis
(AU) Eccentricity
c 2.5 ± 1 ~36,500 23 low


[edit] See also

* PSR 1257+12
* Delta Trianguli
* Pulsar planet

[edit] References

1. ^ WD J1623-266 at SIMBAD
2. ^ PSR B1620-26 at the Extrasolar Planets Encyclopedia

* SolStation: PSR B1620-26
* Extrasolar Visions: PSR B1620-26 A + PSR B1620-26 B
* Z. Arzoumanian, K. Joshi, F. A. Rasio, S. E. Thorsett (1999). "Orbital Parameters of the PSR B1620-26 Triple System". Proceedings of the 160th colloquium of the International Astronomical Union 105: 525.

[edit] External links

* SPACE: Oldest Known World Conjures Prospect of Ancient Life

Sun This binary or multiple star system-related article is a stub. You can help Wikipedia by expanding it.
Retrieved from "http://en.wikipedia.org/wiki/PSR_B1620-26"

Categories: Binary stars | Pulsars | White dwarfs | Scorpius constellation | Multiple star stubs
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