Astronomy:G 240-72

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Short description: Star in the constellation Draco

Coordinates: Sky map 17h 48m 08.17s, +70° 52′ 35.3″

G 240-72
G 240-72 is located in the constellation Draco
G 240-72 is located in the constellation Draco
G 240-72
Location of G 240-72 in the constellation Draco

Observation data
Equinox J2000.0]] (ICRS)
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[1] mas/yr
Dec.: 1108.801[1] mas/yr
Parallax (π)160.9952 ± 0.0119[1] mas
Distance20.259 ± 0.001 ly
(6.2114 ± 0.0005 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
Rotation>100 years[6]
Age5.69[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
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 20.3 light-years away in the 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, 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]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 Holberg, J. B.; Sion; Oswalt; McCook; Foran; Subasavage (2008). "A New Look at the Local White Dwarf Population". The Astronomical Journal 135 (4): 1225–1238. doi:10.1088/0004-6256/135/4/1225. Bibcode: 2008AJ....135.1225H. https://commons.erau.edu/publication/886. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 "GJ 1221 -- White Dwarf". Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=GJ+1221. 
  4. ↑ Van Altena, W. F.; Lee, J. T.; Hoffleit, E. D. (1995). GCTP 2835.01. The General Catalogue of Trigonometric Stellar Parallaxes (Fourth ed.). Bibcode: 1995gcts.book.....V. http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-source=I/238A/picat&GCTP=2835.01. Retrieved 2015-10-10. 
  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. doi:10.1088/0067-0049/199/2/29. Bibcode: 2012ApJS..199...29G. 
  6. ↑ 6.0 6.1 Brinkworth, Carolyn S.; Burleigh, Matthew R.; Lawrie, Katherine; Marsh, Thomas R.; Knigge, Christian (August 2013). "Measuring the Rotational Periods of Isolated Magnetic White Dwarfs". The Astrophysical Journal 773 (1): 47. doi:10.1088/0004-637X/773/1/47. ISSN 0004-637X. Bibcode: 2013ApJ...773...47B. 
  7. ↑ 7.0 7.1 Sion, Edward M.; Holberg, J. B.; Oswalt, Terry D.; McCook, George P.; Wasatonic, Richard (2009). "The White Dwarfs within 20 Parsecs of the Sun: Kinematics and Statistics". The Astronomical Journal 138 (6): 1681–1689. doi:10.1088/0004-6256/138/6/1681. Bibcode: 2009AJ....138.1681S. 

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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