12 Hydrae

12 Hydrae
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension 08h 46m 22.53544s[1]
Declination −13° 32′ 51.7502″[1]
Apparent magnitude (V) 4.32[2]
Characteristics
Spectral type G8 IIIb CN-1[3]
B−V color index 0.900±0.015[2]
Astrometry
Radial velocity (Rv)−8.5±0.7[2] km/s
Proper motion (μ) RA: +18.789[1] mas/yr
Dec.: −18.385[1] mas/yr
Parallax (π)16.1839 ± 0.6646 mas[1]
Distance202 ± 8 ly
(62 ± 3 pc)
Absolute magnitude (MV)+0.26[4]
Orbit[5]
PrimaryAa
CompanionAb
Period (P)1,592±806 d
Semi-major axis (a)0.0116±0.057″
Eccentricity (e)0.40±0.26
Inclination (i)58±10°
Longitude of the node (Ω)91±16°
Periastron epoch (T)49,194±664
Argument of periastron (ω)
(secondary)		103±34°
Details
Mass2.32[6] M☉
Radius11.51+0.18
−0.37[1] R☉
Luminosity77.468±3.553[1] L☉
Temperature4,968±13[6] K
Rotational velocity (v sin i)4.6±0.2[4] km/s
Age910[6] Myr
Other designations
D Hya, 12 Hya, BD−13°2673, HD 74918, HIP 43067, HR 3484, SAO 154622, WDS J08464-1333[7]
Database references
SIMBADdata

12 Hydrae is a probable astrometric binary[8] star system located 202 light years away from the Sun in the equatorial constellation of Hydra. It has the Bayer designation D Hydrae;[7] 12 Hydrae is the Flamsteed designation. This system is visible to the naked eye as a faint, yellow-hued star with a combined apparent visual magnitude of 4.32.[2] It is moving closer to the Earth with a heliocentric radial velocity of −8.5 km/s.[2]

This was found to be a double star by R. A. Rossiter in 1953,[9] with the magnitude 13.7 companion having an angular separation of 26.8″ along a position angle of 266°, as of 2016. The brighter, magnitude 4.32 component A is a spectroscopic binary. As of 2009, the orbital solution for this pair is of low quality, giving a period of roughly 4 years and an eccentricity of around 0.4.[5]

The primary component is an aging giant star with a stellar classification of G8 IIIb CN-1,[3] where the suffix notation indicates an underabundance of the cyanogen molecule. It is 910[6] million years old with 2.32[6] times the mass of the Sun. After exhausting the hydrogen at its core and evolving off the main sequence, the star has swollen to 11.5[1] times the Sun's radius. It is radiating 77[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,968 K.[6]

  1. ^ a b c d e f g h i Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Keenan1989 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference vonEiff2012 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Hartkopf2006 was invoked but never defined (see the help page).
  6. ^ a b c d e f Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Rossiter1953 was invoked but never defined (see the help page).