errors in calculations. In 1994, an additional planet was discovered. Additionally, this system may have an asteroid belt or a Kuiper belt. The planets are believed to be the result of a second round of planetary system formation as a result of two white dwarfs merging with each other into a pulsar and a resulting disk of material in orbit around the star. Other scenarios include unusual supernova remnants or a quark-nova. However, the white dwarf–white dwarf merge model seems to be the most likely cause of the formation of the planets. Retracted claim of fourth orbital body In 1996, a possible Saturn-like (100 Earth mass) gas giant was announced orbiting the pulsar at a distance of about 40 AU. The original hypothesis was retracted and a reinterpretation of the data led to a new hypothesis of a dwarf planet one fifth the size of Pluto orbiting PSR B1257+12 at an average orbital distance of 2.4 AU with an orbital period of approximately 4.6 years. The dwarf planet hypothesis was also retracted because further observations showed that the pulsation anomalies previously thought to reveal a fourth orbital body are "not periodic and can be fully explained in terms of slow changes in the pulsar's dispersion measure". See also 51 Pegasi Gamma Cephei Ab Lists of exoplanets PSR B1620-26 Notes References External links Pulsar Planets PSR 1257+12 on The Extrasolar Planets Encyclopaedia Lytle, Wayne (1992). "Does This Pulsar Have Orbiting Planets?". Cornell Theory Center 01 Science and technology in Poland Virgo (constellation) Planetary systems with three confirmed planets