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] mas |
| Distance | 19.8 ± 0.3 ly (6.07 ± 0.09 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☉ |
| Surface gravity (log g) | 8.36 ± 0.02[2] |
| Temperature | 5590 ± 90[2] K |
| Age | 5.69[note 3][3] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
GJ 1221 (or WD 1748+708, or LHS 455, or G 240-72) is a nearby degenerate star (white dwarf) of spectral class DQP9.0[2], located in constellation Draco. It 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] corresponding to a distance 6.07 ± 0.09 pc, or 19.80 ± 0.30 ly.
GJ 1221 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 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 low temperature.
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