78 Ursae Majoris

78 Ursae Majoris
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 13h 00m 43.69949s[1]
Declination +56° 21′ 58.8102″[1]
Apparent magnitude (V) 4.93[2] (5.02 + 7.88)[3]
Characteristics
Evolutionary stage main sequence
Spectral type F2V[4] + G6V[5]
U−B color index +0.00[6]
B−V color index +0.368±0.010[2]
Astrometry
Radial velocity (Rv)−5.1±0.9[2] km/s
Proper motion (μ) RA: 107.94[1] mas/yr
Dec.: 2.05[1] mas/yr
Parallax (π)39.30 ± 0.38 mas[1]
Distance83.0 ± 0.8 ly
(25.4 ± 0.2 pc)
Absolute magnitude (MV)+2.84[7]
Orbit[8]
Period (P)104.9±0.6 yr
Semi-major axis (a)1.208±0.010″
Eccentricity (e)0.388±0.009
Inclination (i)46.9±0.9°
Longitude of the node (Ω)88.0±1.1°
Periastron epoch (T)B 1921.224±0.403
Argument of periastron (ω)
(secondary)		119.2±1.5°
Details
78 UMa A
Mass1.34[9] M☉
Radius1.62±0.24[10] R☉
Luminosity5.75[2] L☉
Surface gravity (log g)4.26±0.14[9] cgs
Temperature6,908±235[9] K
Metallicity [Fe/H]0.01±0.05[11] dex
Rotation19.2 ± 2.9 h[10]
Rotational velocity (v sin i)91.7±4.6[12] km/s
Age785[9] Myr
Other designations
78 UMa, BD+57°1408, HD 113139, HIP 63503, HR 4931, SAO 28601, WDS J13007+5622[13]
Database references
SIMBADThe system
A
B

78 Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.93.[13] Parallax estimates by Hipparcos put it at a distance of 83 light-years (25 pc),[1] but it is drifting closer with a radial velocity of −5 km/s.[2] The system is a candidate member of the Ursa Major Moving Group.[14]

The binary nature of this system was announced by S. W. Burnham in 1894.[15] The pair orbit each other with a period of 105 years and an eccentricity of 0.39. Their semimajor axis has an angular size of 1.2″ and the orbital plane is inclined by 47°.[8]

The primary member, designated component A, has a magnitude of 5.02[3] and is an F-type main-sequence star with a stellar classification of F2V.[4] It is 785[9] million years old and is spinning with a projected rotational velocity of 92 km/s.[12] The star has 1.34[9] times the mass of the Sun and is radiating 5.75[2] times the Sun's luminosity from its photosphere at an effective temperature of 6,908 K.[9]

The secondary, designated component B, has a visual magnitude of 7.88.[3] It is a G-type main-sequence star with a class of G6V.[5] The star is a suspected variable.[16]

  1. ^ a b c d e f Cite error: The named reference HIP was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Fabricius was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gray was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Edwards1976 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference EgUBV was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Eggen1998 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Drummond2014 was invoked but never defined (see the help page).
  9. ^ a b c d e f g Cite error: The named reference David2015 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Justesen_Albrecht_2020 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference gaspar2016 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference vonEiff2012 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference nakajima2012 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference ORB6 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Baize1989 was invoked but never defined (see the help page).