Psi Big Dipper

Psi Big Dipper ( lat. Psi Ursae Majoris , Ursae Majoris , UMa ) is a star in the northern constellation Ursa Major . It has an apparent magnitude of +3.01, ^[2] while the star is visible with the naked eye and is one of the brightest stars in the constellation. Parallax measurements provide an estimate of the distance of 144.5 light years (44.3 parsec ) from the Sun. ^[1] This is a fairly close distance, so the star's brightness is attenuated only by approximately 0.05 stellar magnitude due to interstellar extinction ^[3] . In Chinese astronomy, the star is called Tien Tsan or Ta Tsun , "Very Honorable." ^[11] The name may have come from the word 太 尊, pinyin : Tàizūn, which means royal , since the star is very prominent.

ψ Ursa Major
Star
Observational data ( Epoch J2000.0 )
Right ascension
Declination
Distance	144.5 sv. of the year
Visible magnitude ( V )	+3.01 [2]
Constellation
Astrometry
Radial velocity ( R v )	–3.39 [3] km / s
Proper motion (μ)	RA: –62.02 [1] mas per year Dec: –27,41 [1] mas per year
Parallax (π)	22.57 ± 0.14 [1] mas
Absolute magnitude (V)	−0.27 [4]
Specifications
Spectral class	K1III [5]
Color Indicator ( B - V )	+1.14 [2]
Color Index ( U - B )	+1.12 [2]
physical characteristics
Radius	19.7 ± 0.6 [6] R ☉
Age	1.11 ± 0.39 [7] billion years
Temperature	4520 [5] K
Luminosity	148 ± 12 [6] L ☉
Metallicity	from –0.13 [6] to 0.16 [5]
Rotation	5.5 [8] km / s
Other designations ψ Ursae Majoris, ψ UMa, Psi UMa, 52 Ursae Majoris, BD +45 1897, FK5 420, GC 15340, HD 96833, HIP 54539, HR 4335, PPM 52277, SAO 43629. [9]
Information in databases
SIMBAD	data

The spectrum of the star corresponds to the spectral class K1 III, ^[5] the luminosity class 'III' means that the star is a giant that has exhausted the supply of hydrogen in the core. Consequently, the star has expanded to 20 ^{[6] the} radii of the Sun. The luminosity in 148 ^[6] exceeds the solar, the external atmosphere has an effective temperature of 4520 K ^[5]. At this temperature, the star has an orange color of the surface. ^[12] .

Psi Big Dipper is a representative of the population of the Milky Way thin disk . It is in orbit with a small eccentricity of 0.02, as a result of which the distance from the star to the center of the Galaxy varies from 26.5 to 27.8 thousand light years. A small orbital inclination means that the star is only 130 light years away from the galactic plane . ^[7]