Pulsar planet in the context of "Extrasolar planets"

PSR B1257+12, alternatively designated PSR J1300+1240, is a millisecond pulsar, 2,300 light-years (710 parsecs) from the Sun, in the constellation Virgo, rotating at 160.8 times per second (faster than the blade of a blender). It is also named Lich, after a powerful, fictional undead creature.

The pulsar has a planetary system with three known pulsar planets, named "Draugr" (PSR B1257+12 b or PSR B1257+12 A), "Poltergeist" (PSR B1257+12 c, or PSR B1257+12 B), and "Phobetor" (PSR B1257+12 d, or PSR B1257+12 C). They were both the first extrasolar planets to be discovered and the first pulsar planets to be discovered—B and C in 1992 and A in 1994. A is the lowest-mass planet yet discovered by any observational technique, having somewhat less than twice the mass of Earth's moon.

PSR B1257+12 b, alternatively designated PSR B1257+12 A, also named Draugr, is an extrasolar planet approximately 2,300 light-years (710 pc) away in the constellation of Virgo. The planet is the innermost object orbiting the pulsar Lich, making it a pulsar planet in the dead stellar system. It is about twice as massive as the Moon, and is listed as the least massive planet (with the mass accurately determined) known, including among the planets in the Solar System.

PSR B1257+12 c, alternatively designated PSR B1257+12 B, also named Poltergeist, is an extrasolar planet approximately 2,300 light-years away in the constellation of Virgo. It was one of the first planets ever discovered outside the Solar System, and is one of three pulsar planets known to be orbiting the pulsar Lich.

Over four times as massive as the Earth, it circles the primary at a distance of 0.36 AU with an orbital period of approximately 66 days. Because it and Phobetor have very similar masses and orbit close to each other, they were expected to cause measurable perturbations in each other's orbits. Detecting such perturbations confirmed that the planets were real. Accurate masses of the two planets, as well as their inclinations, were calculated from how much the planets perturb each other.