Phecda

"Phad" redirects here. For scroll painting style, see Phad painting.
Phecda
Location of Phecda (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 11h 53m 49.84732s[1]
Declination +53° 41′ 41.1350″[1]
Apparent magnitude (V) 2.438[2]
Characteristics
Spectral type A0 Ve + K2 V[3]
U−B color index +0.008[2]
B−V color index –0.013[2]
Astrometry
Radial velocity (Rv)−12.6[4] km/s
Proper motion (μ) RA: +107.68[1] mas/yr
Dec.: +11.01[1] mas/yr
Parallax (π)39.21 ± 0.40 mas[1]
Distance83.2 ± 0.8 ly
(25.5 ± 0.3 pc)
Absolute magnitude (MV)0.4[5]
Orbit[5]
Period (P)20.5 ± 1 yr
Semi-major axis (a)0.460″
Eccentricity (e)0.3 ± 0.3
Inclination (i)51 ± 15°
Longitude of the node (Ω)6 ± 61°
Periastron epoch (T)B 1984.0 ± 2.0
Argument of periastron (ω)
(secondary)		185 ± 37°
Details[6]
γ UMa A
Mass2.412+0.053
−0.060 M☉
Radius3.385 (equatorial)
2.186 (polar) R☉
Luminosity44.57+3.39
−3.61 L☉
Surface gravity (log g)3.79[7] cgs
Temperature6,751 (equatorial)
10,520 (polar) K
Rotational velocity (v sin i)184.5+32.6
−35.6 km/s
Age333+43
−83 Myr
γ UMa B
Mass0.79[3] M☉
Luminosity0.397[3] L☉
Temperature4,780[3] K
Other designations
Phad, Phecda, Phekda, Phegda, Phekha, Phacd, Fekda,[8] γ Ursae Majoris, γ UMa, Gamma UMa, 64 Ursae Majoris, BD+54 1475, FK5 447, GC 16268, HD 103287, HIP 58001, HR 4554, PPM 33292, SAO 28179.[9]
Database references
SIMBADdata

Phecda /ˈfɛkdə/, also called Gamma Ursae Majoris (γ Ursae Majoris, abbreviated Gamma UMa, γ UMa),[10][11] is a star in the constellation of Ursa Major. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[12] Based upon parallax measurements with the Hipparcos astrometry satellite,[13][14] it is located at a distance of around 83.2 light-years (25.5 parsecs) from the Sun.[1]

It is more familiar to most observers in the northern hemisphere as the lower-left star forming the bowl of the Big Dipper, together with Alpha Ursae Majoris (Dubhe, upper-right), Beta Ursae Majoris (Merak, lower-right) and Delta Ursae Majoris (Megrez, upper-left). Along with four other stars in this well-known asterism, Phecda forms a loose association of stars known as the Ursa Major moving group.[7] Like the other stars in the group, it is a main sequence star, as the Sun is, although somewhat hotter, brighter and larger.

Phecda is located in relatively close physical proximity to the prominent Mizar–Alcor star system. The two are separated by an estimated distance of 8.55 ly (2.62 pc); much closer than the two are from the Sun. The star Merak is separated from Phecda by 11.0 ly (3.4 pc).[15]

  1. ^ a b c d e f Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference aaass65_2_405 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Eggl was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference scfs was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Gontcharov was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Jones was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference aj125_4_1980 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference allen1899 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  11. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  12. ^ Cite error: The named reference baas25_1319 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference aaa323_L49 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference GSM was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference apjss192_1_2 was invoked but never defined (see the help page).