HM Cancri: Difference between revisions

}}</ref> It comprises two dense [[white dwarf]]s orbiting each other once every 321.5&nbsp;seconds (in this system the "year" duration is of only 5.4 minutes), at an estimated distance of only {{convert|80000|km|miles}} apart (about 1/5 the distance between the Earth and the Moon). The two stars orbit each other at speeds in excess of {{convert|400|km/s|mph}}. The stars are estimated to be about half as massive as the [[Sun]]. Like typical white dwarfs, they are extremely dense, being composed of degenerate matter, and so have radii of orderon the radiusorder of the Earth's radius. Astronomers believe that the two stars will eventually merge, based on data from many X-ray satellites, such as [[Chandra X-Ray Observatory]], [[XMM-Newton]] and the [[Swift Gamma-Ray Burst Mission]]. These data show that the orbital period of the two stars is steadily decreasing at a rate of 1.2&nbsp;milliseconds per year as they thus are getting closer by approximately {{convert|60|cm|ft}} per day. At this rate, they can be expected to merge in approximately 340,000 years. With a revolution period of 5.4 minutes, RX J0806.3+1527 is the shortest orbital period binary system currently known.