HD 189245

HD 189245 is the Henry Draper catalogue designation for a solitary^[11] star in the southern constellation of Sagittarius. It has an apparent visual magnitude of 5.66,^[2] which means it is faintly visible to the naked eye. Parallax measurements from the Hipparcos satellite indicate a distance of 72 light years from the Sun.^[1] It is drifting closer with a heliocentric radial velocity of −13 km/s.^[5]

HD 189245

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	20h 00m 20.249s[1]
Declination	−33° 42′ 12.42″[1]
Apparent magnitude (V)	5.66[2]
Characteristics
Spectral type	F8.5 V Fe−0.6 CH−0.5[3]
U−B color index	−0.04[2]
B−V color index	+0.498[4]
Astrometry
Radial velocity (Rv)	−13.2[5] km/s
Proper motion (μ)	RA: +128.794 mas/yr[1] Dec.: −289.360 mas/yr[1]
Parallax (π)	45.1537±0.0551 mas[1]
Distance	72.23 ± 0.09 ly (22.15 ± 0.03 pc)
Absolute magnitude (MV)	4.06[6]
Details
Mass	1.3[7] M☉
Radius	1.2[7] R☉
Luminosity	2.2[7] L☉
Surface gravity (log g)	4.31[3] cgs
Temperature	6,333[3] K
Metallicity [Fe/H]	−0.09[3] dex
Rotational velocity (v sin i)	72.6[8] km/s
Age	100 or 500[4] Myr
Other designations
262 G. Sgr[9], CD−34°14082, GJ 773.4, GJ 9679, HD 189245, HIP 98470, HR 7631, SAO 211724[10]
Database references
SIMBAD	data

The stellar classification of this star is F8.5 V Fe−0.6 CH−0.5,^[3] indicating that it is an F-type main sequence star with a spectrum that shows deficiencies in iron (Fe) and methylidyne (CH) in its outer atmosphere. It is a variable star with an active chromosphere and is a source of X-ray emission.^[3][12] HD 189245 is spinning rapidly with a projected rotational velocity of 72.6^[8] km/s. Gyrochronology indicates this is a young star with an estimated age of 500 million years. However, the amount of X-ray emission suggests an even younger star that is roughly 100 million years old.^[4]

The velocity components of HD 189245 indicate that it is a likely member of the AB Doradus moving group of stars, which share a common motion through space. This group has an age of around 50 million years and is centered at a point 98 ly (30 pc) from the Sun.^[13]