Phi Ursae Majoris

Phi Ursae Majoris
Phi Ursae Majoris is located in 100x100
Phi Ursae Majoris

Location of φ Ursae Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 09h 52m 06.35437s[1]
Declination +54° 03′ 51.5962″[1]
Apparent magnitude (V) +4.60[2] (5.28 + 5.39)[3]
Characteristics
Spectral type A3 IV + A3 IV[4]
U−B color index +0.08[2]
B−V color index +0.03[2]
Astrometry
Radial velocity (Rv)−14.7±0.3[5] km/s
Proper motion (μ) RA: −6.00[1] mas/yr
Dec.: +19.16[1] mas/yr
Parallax (π)6.41 ± 0.59 mas[1]
Distance510 ± 50 ly
(160 ± 10 pc)
Absolute magnitude (MV)−1.39[6]
Orbit[7]
Period (P)104.6 yr
Semi-major axis (a)0.329″
Eccentricity (e)0.436
Inclination (i)19.4°
Longitude of the node (Ω)132.5°
Periastron epoch (T)1987.52
Argument of periastron (ω)
(secondary)		33.3°
Details
A
Mass3.5±0.2[8] M☉
Luminosity347[8] L☉
Surface gravity (log g)3.69±0.16[9] cgs
Temperature8,769±150[9] K
Metallicity [Fe/H]−0.23±0.08[9] dex
Rotational velocity (v sin i)28[8] km/s
Other designations
φ UMi, 30 Ursae Majoris, BD+54°1331, GC 13559, HD 85235, HIP 48402, HR 3894, SAO 27408, PPM 32355, CCDM J09521+5404AB, WDS J09521+5404AB[10]
Database references
SIMBADdata

Phi Ursae Majoris, Latinized from φ Ursae Majoris, is binary star[11] system in the northern constellation of Ursa Major. It is white-hued and is visible to the naked eye with a combined apparent visual magnitude of +4.60;[2] the primary is magnitude 5.28 while the secondary is magnitude 5.39.[11] The system is located at a distance of approximately 510 light-years (160 parsecs) from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −14.7 km/s.[5] It should make its closest approach at a distance of around 370 light-years in about 4.7 million years.[6]

As of 2017, the components had an angular separation of 0.50″ along a position angle of 304°.[3] They are orbiting each other with a period of 105.4 years and eccentricity of 0.44.[7] Both of components are A-type subgiant stars[12] with a stellar classification of A3 IV.[4]

Phi Ursae Majoris is moving through the galaxy at a speed of 21.6 km/s relative to the Sun. Its projected galactic orbit carries it between 24,000 and 46,000 light-years from the center of the galaxy.[6]

  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 Cite error: The named reference Johnson1966 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference WDSC2014 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Edwards1976 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Hartkopf2006 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference aaa537_A120 was invoked but never defined (see the help page).
  9. ^ a b c Cite error: The named reference prugniel2011 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Simbad was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference kaler was invoked but never defined (see the help page).