G 240-72
Coordinates: 
17h 48m 08.17s, +70° 52′ 35.3″
| Observation data Epoch J2000[1] Equinox J2000[1] |
|
|---|---|
| Constellation | Draco |
| Right ascension | 17h 48m 08.17s[1] |
| Declination | +70° 52′ 35.3″[1] |
| Apparent magnitude (V) | 14.15[2] |
| Characteristics | |
| Spectral type | DQP9.0[2] |
| Apparent magnitude (B) | 14.55[1] |
| Apparent magnitude (V) | 14.15[1] |
| Apparent magnitude (R) | 13.5[1] |
| Apparent magnitude (I) | 13.1[1] |
| Apparent magnitude (J) | 12.709 ± 0.021[1] |
| Apparent magnitude (H) | 12.528 ± 0.023[1] |
| Apparent magnitude (K) | 12.507 ± 0.023[1] |
| Astrometry | |
| Proper motion (μ) | RA: -1261[3] mas/yr Dec.: 1112[3] mas/yr |
| Parallax (π) | 164.7 ± 2.4[4]:{{{3}}} mas |
| Distance | 19.8 ± 0.3 ly (6.07 ± 0.09 pc) |
| Absolute magnitude (MV) | 15.23[2][4]:{{{3}}}[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 |
| Age | 5.69[note 3][3] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
G 240-72 (or WD 1748+708, or LHS 455, or GJ 1221) is a nearby degenerate star (white dwarf) of spectral class DQP9.0,[2] located in constellation Draco.
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 is 0.1647 ± 0.0024 arcsec,[4]:{{{3}}} corresponding to a distance 6.07 ± 0.09 pc, or 19.80+0.29
−0.28 ly.
Properties
G 240-72 has mass 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 relatively low temperature 5590 K[2] (slightly cooler than the Sun), and old cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star) 5.69 Gyr.[3] Despite it is classified as "white dwarf", it should appear yellow, not white, due to low temperature.
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 3.2 3.3 3.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 4.0 4.1 4.2 4.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
Notes
- ↑ From apparent magnitude and parallax.
- ↑ From surface gravity and mass.
- ↑ Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)
