G 240-72
Star in the constellation Draco
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G 240-72 (or WD 1748+708, or LHS 455, or GJ 1221) is a nearby white dwarf (degenerate star) of spectral class DQP9.0,[2] located 20.3 light-years away in the constellation Draco.
  G 240-72 Location of G 240-72 in the constellation Draco | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 17h 48m 07.99282s[1] |
| Declination | +70° 52′ 35.9221″[1] |
| Apparent magnitude (V) | 14.15[2] |
| Characteristics | |
| Evolutionary stage | white dwarf[2] |
| Spectral type | DQP9.0[2] |
| Apparent magnitude (B) | 14.55[3] |
| Apparent magnitude (V) | 14.15[3] |
| Apparent magnitude (R) | 13.5[3] |
| Apparent magnitude (I) | 13.1[3] |
| Apparent magnitude (J) | 12.709 ± 0.021[3] |
| Apparent magnitude (H) | 12.528 ± 0.023[3] |
| Apparent magnitude (K) | 12.507 ± 0.023[3] |
| Astrometry | |
| Proper motion (μ) | RA: −1266.387 mas/yr[1] Dec.: 1108.801 mas/yr[1] |
| Parallax (π) | 160.9952±0.0119 mas[1] |
| Distance | 20.259 ± 0.001 ly (6.2114 ± 0.0005 pc) |
| Absolute magnitude (MV) | 15.23[2][4][note 1] |
| Details | |
| Mass | 0.81 ± 0.01[2] M☉ |
| Radius | 0.00984[2][note 2] R☉ |
| Luminosity | 0.000085[5] L☉ |
| Surface gravity (log g) | 8.36 ± 0.02[2] cgs |
| Temperature | 5590 ± 90[2] K |
| Rotation | >100 years[6] |
| Age | 5.69[note 3][7] Gyr |
| Other designations | |
| GJ 1221, EGGR 372, G 240-72, LHS 455, LP 44-113, NLTT 45565, WD 1748+708, 2MASS J17480817+7052353[3] | |
| Database references | |
| SIMBAD | data |
Distance
G 240-72 is the seventh closest white dwarf (after Sirius B, Procyon B, van Maanen's star, Gliese 440, 40 Eridani B and Stein 2051 B). Its trigonometric parallax, as measured by the Gaia space telescope, is 160.9952±0.0119 mas,[1] corresponding to a distance of 6.2114 parsecs (20.259 light-years).
Properties
G 240-72 has a mass of 0.81 Solar masses[2] and surface gravity 108.36 (2.29×108) cm·s−2,[2] or approximately 234 000 of Earth's, corresponding to a radius 6850 km, or 107% of Earth's.
This white dwarf has a relatively low temperature of 5590 K[2] (slightly cooler than the Sun), and an old cooling age, i.e. the age as a degenerate star (not counting the duration of its previous existence as a main sequence and giant star) of 5.69 Gyr.[7] It has a white appearance, due to its similar temperature to the Sun. It has a pure helium atmosphere and rotates very slowly, with period of possibly over 100 years.[6]