81 Ursae Majoris, a blue main-sequence star in Ursa Major

81 Ursae Majoris (HIP 66198)

81 Ursae Majoris is a blue main-sequence star in the constellation Ursa Major. At 298 light years away, it shines at an apparent visual magnitude of 5.60. It is moving through the Galaxy at a speed of 11.2 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,800 and 27,000 light years from the center of the Galaxy. It will come closest to the Sun 5.0 million years from now when it will brighten to magnitude 5.07 from a distance of 234 light years.

Sky position: RA 13h 34.1m, Dec +55° 21'

Common designations: 81 Ursae Majoris, HIP 66198, HD 118214, HR 5109

Galactic Orbit of 81 Ursae Majoris
(compared to the Sun)

E

ccentricity: 6.3% vs. 16.0%

Angle φ : 42.3°vs. 26.0°

Semi-major axis : 7,793 pc vs. 8,686 pc

Semi-minor axis: 7,778 pc vs. 8,574 pc

Focus-to-center

: 492 pcvs. 1,388 pc

Semilatus rectum : 7,762 pc vs. 8,464 pc

Perigalacticon: 7,302 pc vs. 7,297 pc

Apogalacticon

: 8,285 pcvs. 10,074 pc
  Some Tabulated XHIP Data for 81 Ursae Majoris
(see also: SIMBAD)

Astrometry
2007A&A...474..653V

Position	Proper Motion
Right Ascension:	203.53052089° ±0.20 mas	-19.41 ±0.25 mas/yr.
Declination:	55.34844977° ±0.22 mas	-5.93 ±0.25 mas/yr.
Galactic Longitude:	110.49373267°	16.27 mas/yr.
Galactic Latitude:	60.73707054°	12.13 mas/yr.

Parallax: 10.92 ± 0.26 mas

Spectrography

Spectral Type: B9.5V 1995ApJS...99..135A.

Radial Velocity: -7.00 ±7.40 km/s [B rating] 2007AN....328..889K.

Iron Abundance [Fe/H]: n/a

Photometry
 

band	magnitude	Abs. Mag.
U
B	5.59	0.78
V	5.60	0.79
R
I	5.58	0.77
J	5.60	0.79
H	5.65	0.85
K	5.64	0.83

B-V: -0.01 V-I: +0.02

Derivations

Heliocentric distance: 91.51 pc (2.4% margin of error)

Galactocentric distance: 7,416 pc

Transverse velocity: 8.8 km/s

3D heliocentric position and motion:

toward:	Galactic center	Galactic rotation	North Galactic Pole
Position ( X, Y, Z)	-15.7 pc	41.9 pc	79.8 pc
Velocity (U, V, W)	-3.8 km/s	-10.0 km/s	-3.5 km/s