|Right ascension||08h 06m 23.20s|
|Declination||+15° 27' 30.20"|
|Period (P)||321.5 seconds|
|Mass||0.5 (primary) / 0.5 (b) M☉|
RX J0806.3+1527, RX J0806, J0806, HM Cancri, HM Cnc
RX J0806.3+1527 or HM Cancri (sometimes shortened to HM Cnc or J0806 after establishing identity) is an X-ray binary star system about 1,600 light-years (490 pc) away. It comprises two dense white dwarfs orbiting each other once every 321.5 seconds, at an estimated distance of only 80,000 kilometres (50,000 mi) apart (about 1/5 the distance between the Earth and the Moon). The two stars orbit each other at speeds in excess of 400 kilometres per second (890,000 mph). The stars are estimated to be about half as massive as our own Sun. Like typical white dwarfs, they are extremely dense, being composed of degenerate matter, and so have radii of order the radius of Earth. Astronomers believe that the two stars will eventually merge, based on data from the Chandra X-Ray Observatory, which shows that the orbital period of the two stars is steadily decreasing at a rate of 1.2 milliseconds per year as they thus are getting closer by approximately 60 centimetres (2.0 ft) per day.
As RX J0806.3+1527 is a pair of white dwarfs, it has a relatively low luminosity, and so can not be observed directly at this time. Instead, scientists make observations by recording the X-rays emitted. It is by this method that scientists were able to determine their orbital period as the magnitude of the X-rays spikes every 321.5 s.
Relation to general relativity
The decreasing separation of the components of the system mean that the system is losing orbital energy. Albert Einstein's theory of General Relativity predicts such a system will lose orbital energy through the generation of gravitational waves. Scientists believe that RX J0806.3+1527 may be the largest source of gravitational waves in the Galaxy.
- "RX J0806.3+1527: Orbiting Stars Flooding Space with Gravitational Waves". CHANDRA X-RAY OBSERVATORY, Harvard. 2005-05-30. Archived from the original on 2005-05-30. Retrieved 2013-05-31.
- APOD 2005 June 1 - White Dwarf Star Spiral
- NASA Sees Orbiting Stars Flooding Space With Gravitational Waves
- RX J0806.3+1527: Orbiting Stars Flooding Space with Gravitational Waves
- Monitoring the spin up in RX J0806+15
- Phase Coherent Timing of RX J0806.3+1527 with ROSAT and Chandra
- RX J0806
- RX J0806.3+1527 Gravitational Wave Merger
- SPECTROSCOPIC EVIDENCE FOR A 5.4-MINUTE ORBITAL PERIOD IN HM CANCRI