PSR B1620-26 is also called PSR J1623-2631 (or 16:23:38.22-23:31:53.8 J2000 or 16:23:38.24-26:31:53.9, ICRS 2000)
System Configuration
PSR B1620-26 is a pulsar in the globular cluster Messier 4 (or M4: see Messier object), about 5,600 light years from Earth in the constellation Scorpius.
PSR B1620-26b is a white dwarf companion to the pulsar primary.
PSR B1620-26c is a planet orbitting the primary and secondary in a circumbinary orbit. This makes the system the only triple system radio pulsar, and the only triple system in a gobular cluster known thus far.
System Notes
A planet was discovered in this system, and has been designated PSR B1620-26c, but it does not yet have an official name; Methuselah is only a nickname not yet accepted by the International Astronomical Union.
It is theorized that originally B1620-26 had another, lower mass white dwarf companion, which was ejected when the current B1620-26b interacted with the original binary system. At that time, B1620-26b was still a main sequence star, with B1620-26c as its planet. 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.
See Also
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