GRW +70 8247
Star in the constellation Draco
From Wikipedia, the free encyclopedia
GRW +70 8247 is a white dwarf star located 42 light-years from Earth[1] in the constellation Draco. With a magnitude of about 13 it is visible only through a large telescope.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Draco |
| Right ascension | 19h 00m 10.2534s[1] |
| Declination | +70° 39′ 51.418″[1] |
| Apparent magnitude (V) | 13.19[2] |
| Characteristics | |
| Spectral type | DAP4.5[3] |
| U−B color index | -0.85[4] |
| B−V color index | +0.05[4] |
| Astrometry | |
| Proper motion (μ) | RA: +85.774[1] mas/yr Dec.: +505.050[1] mas/yr |
| Parallax (π) | 77.6525±0.0317 mas[1] |
| Distance | 42.00 ± 0.02 ly (12.878 ± 0.005 pc) |
| Details[5] | |
| Mass | 1.029 M☉ |
| Radius | 5,960[a] km |
| Luminosity | 0.013182 L☉ |
| Surface gravity (log g) | 8.67 cgs |
| Temperature | 12540±143 K |
| Age | (as white dwarf) 1.138 Gyr |
| Other designations | |
| GJ 742, AC +70 8247, G 260-15, LFT 1446, LHS 3424, LTT 15585, Grw+70 8247, WD 1900+705[2][6] | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Properties
Although photographed in the 19th century as part of the Carte du Ciel project, the star was not determined to be a white dwarf until G. P. Kuiper observed it in 1934.[7] This makes it the fifth or sixth white dwarf discovered.[b] At first, its spectrum was thought to be almost featureless,[7] but later observation showed it to have unusual broad, shallow absorption bands.[11][12] In 1970, when light that it emitted was observed to be circularly polarized, it became the first white dwarf known to have a magnetic field.[13][14] In the 1980s, it was realized that the unusual absorption bands could be explained as hydrogen absorption lines shifted by the Zeeman effect.[6][15][16]
Notes
- Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
- .
