RX J0439.8−6809
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Dorado |
| Right ascension | 04h 39m 49.64s |
| Declination | −68° 09′ 1.4″ |
| Characteristics | |
| Evolutionary stage | White dwarf |
| Astrometry | |
| Distance | 30,000 ly (9,200 pc) |
| Details | |
| Mass | 0.73-1.02 M☉ |
| Radius | 0.0015 R☉ |
| Temperature | 250,000 K |
| Age | 4.2 Myr |
| Other designations | |
| RX J0439.8-6809, 1RXS J043950.4-680854, 1ES 0439-68.2 | |
| Database references | |
| SIMBAD | data |
RX J0439.8-6809 is a white dwarf located 9.2 kiloparsecs from Earth in the galactic halo of the Milky Way galaxy. It is currently the hottest known white dwarf with a temperature of 250,000 Kelvin. This record surpassed H1504+65, the previous hottest known white dwarf which has a temperature of 200,000 Kelvin. It is not actively nuclear burning and is on the hot end of the white dwarf cooling track (WD cooling track), however it is cooling rather slowly, getting cooler every year by 35 Kelvin and taking 66 years for it to see a 1% change in the flux of UV/Optical. Its mass is not well defined but ranges between 0.73 and 1.02 solar masses and has a radius of 0.0015 Solar radii. The high mass of RX J0439.8-6809 could be due to a collision between two white dwarfs with a minimum mass of 0.5 solar masses.