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G 240-72

Coordinates: Sky map 17h 48m 08.17s, +70° 52′ 35.3″
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G 240-72
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 mas[4]
Distance19.8 ± 0.3 ly
(6.07 ± 0.09 pc)
Absolute magnitude (MV)15.23[2][4][note 1]
Details
Mass0.81 ± 0.01[2] M☉
Radius0.00984[2][note 2] R☉
Luminosity0.000085[5] L☉
Surface gravity (log g)8.36 ± 0.02[2] cgs
Temperature5590 ± 90[2] K
Age5.69[note 3][3] Gyr
Other designations
WD 1748+708,[2][3] LHS 455,[2] LP 44-113,[1] NLTT 45565,[1] GJ 1221,[4] EGGR 372,[1] 2MASS J17480817+7052353[1]
Database references
SIMBADdata

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] 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. ^ a b c d e f g h i j k l m n o "GJ 1221 -- White Dwarf". Centre de Données astronomiques de Strasbourg. Retrieved 2011-10-23.
  2. ^ a b c d e f g h i j k l m Holberg, J. B.; Sion; Oswalt; McCook; Foran; Subasavage (2008). "A NEW LOOK AT THE LOCAL WHITE DWARF POPULATION". The Astronomical Journal. 135: 1225–1238. Bibcode:2008AJ....135.1225H. doi:10.1088/0004-6256/135/4/1225.
  3. ^ a b c d e Sion, Edward M.; Holberg; Oswalt; McCook; Wasatonic (2009). "THE WHITE DWARFS WITHIN 20 PARSECS OF THE SUN: KINEMATICS AND STATISTICS". The Astronomical Journal. 138: 1681–1689. arXiv:0910.1288. Bibcode:2009AJ....138.1681S. doi:10.1088/0004-6256/138/6/1681.
  4. ^ a b c d Van Altena W. F.; Lee J. T.; Hoffleit E. D. (1995). "GCTP 2835.01". The General Catalogue of Trigonometric Stellar Parallaxes (Fourth ed.).
  5. ^ Giammichele, N.; Bergeron, P.; Dufour, P. (April 2012), "Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs", The Astrophysical Journal Supplement, 199 (2): 29, arXiv:1202.5581, Bibcode:2012ApJS..199...29G, doi:10.1088/0067-0049/199/2/29.

Notes

  1. ^ From apparent magnitude and parallax.
  2. ^ From surface gravity and mass.
  3. ^ Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)


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