| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Pronunciation | /æˈluːlə ɔːˈstreɪlɪs/[1] |
| ξ UMa A | |
| Right ascension | 11h 18m 10.902s[2] |
| Declination | +31° 31′ 44.98″[2] |
| Apparent magnitude (V) | 4.264[2] |
| ξ UMa B | |
| Right ascension | 11h 18m 10.950s[2] |
| Declination | +31° 31′ 45.74″[2] |
| Apparent magnitude (V) | 4.729[2] |
| Characteristics | |
| Spectral type | F8.5:V / G2V[3] |
| U−B color index | 0.04[4] |
| B−V color index | 0.59[4] |
| Variable type | RS CVn[5] |
| Astrometry | |
| Radial velocity (Rv) | −18.2±2.7[6] km/s |
| Proper motion (μ) | RA: −339.398 mas/yr[7] Dec.: −607.892 mas/yr[7] |
| Parallax (π) | 114.4867 ± 0.4316 mas[7] |
| Distance | 28.5 ± 0.1 ly (8.73 ± 0.03 pc) |
| ξ UMa Aa | |
| Absolute magnitude (MV) | 4.66[note 1] |
| Absolute bolometric magnitude (Mbol) | 4.54±0.06[8] |
| ξ UMa Ba | |
| Absolute magnitude (MV) | 5.16[note 2] |
| Absolute bolometric magnitude (Mbol) | 5.00±0.06[8] |
| Orbit[9] | |
| Primary | ξ UMa A |
| Companion | ξ UMa B |
| Period (P) | 59.878 yr |
| Semi-major axis (a) | 2.536″ |
| Eccentricity (e) | 0.398 |
| Inclination (i) | 127.94° |
| Longitude of the node (Ω) | 101.85 (ascending)° |
| Periastron epoch (T) | 1935.195 |
| Orbit[9] | |
| Primary | ξ UMa Aa |
| Companion | ξ UMa Ab |
| Period (P) | 1.832 yr |
| Semi-major axis (a) | 0.057″ |
| Eccentricity (e) | 0.53 |
| Inclination (i) | 94.9° |
| Details[8] | |
| ξ UMa Aa | |
| Mass | 0.97 M☉ |
| Radius | 1.02±0.04 R☉ |
| Luminosity | 1.21 L☉ |
| Surface gravity (log g) | 4.39±0.10 cgs |
| Temperature | 6,005±80 K |
| Rotational velocity (v sin i) | 1.0±1.0 km/s |
| ξ UMa Ab | |
| Mass | 0.38±0.02 M☉ |
| Radius | 0.32 R☉ |
| Temperature | ~3,700[note 3] K |
| ξ UMa Ba | |
| Mass | 0.86 M☉ |
| Radius | 0.92±0.04 R☉ |
| Luminosity | 0.79 L☉ |
| Surface gravity (log g) | 4.46±0.10 cgs |
| Temperature | 5,692±90 K |
| Metallicity [Fe/H] | −0.35±0.08 dex |
| Rotational velocity (v sin i) | 3.0±1.0 km/s |
| ξ UMa Bb | |
| Mass | 0.14+0.05 −0.09 M☉ |
| Other designations | |
Alula Australis, ξ Ursae Majoris, ξ UMa, Xi UMa, 53 Ursae Majoris, BD+32°2132, GC 15537, GJ 423, HIP 55203, SAO 62484, CCDM J11182+3132, WDS J11182+3132 | |
| A: HD 98231, HR 4375 | |
| B: HD 98230, HR 4374 | |
| E: WISE J111838.70+312537.9 | |
| Database references | |
| SIMBAD | ξ UMa |
| ξ UMa AB | |
| ξ UMa A | |
| ξ UMa B | |
| ξ UMa Bb | |
| WISE J1118+3125 | |
Xi Ursae Majoris is a quintuple star system 28.5 light-years (8.7 parsecs) away in the constellation of Ursa Major. It has the traditional name Alula Australis;[1][10] Xi Ursae Majoris is the Bayer designation, which is Latinised from ξ Ursae Majoris and abbreviated Xi UMa or ξ UMa. It was the first visual double star for which an orbit was calculated, when it was computed by Félix Savary in 1828.[citation needed] It is also a variable star with a small amplitude. Xi Ursae Majoris is found in the left hind paw of the Great Bear.[11]
- ^ a b 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.
- ^ a b c d e f Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
- ^ Keenan, Philip C; McNeil, Raymond C (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
- ^ a b Nicolet, B (1978). "Catalogue of homogeneous data in the UBV photoelectric photometric system". Astronomy and Astrophysics. 34: 1. Bibcode:1978A&AS...34....1N.
- ^ Dempsey, Robert C; Linsky, Jeffrey L; Fleming, Thomas A; Schmitt, J. H. M. M (1993). "The ROSAT All-Sky Survey of active binary coronae. I - Quiescent fluxes for the RS Canum Venaticorum systems". Astrophysical Journal Supplement Series. 86: 599. Bibcode:1993ApJS...86..599D. doi:10.1086/191791.
- ^ Nordström, B.; et al. (2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ~14000 F and G dwarfs". Astronomy and Astrophysics. 418 (3): 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. S2CID 11027621.
- ^ a b Cite error: The named reference
GaiaDR2was invoked but never defined (see the help page). - ^ a b c Fuhrmann, Klaus (2008). "Nearby stars of the Galactic disc and halo - IV". Monthly Notices of the Royal Astronomical Society. 384 (1): 173–224. Bibcode:2008MNRAS.384..173F. doi:10.1111/j.1365-2966.2007.12671.x.
- ^ a b Cite error: The named reference
aj109_1669_332was invoked but never defined (see the help page). - ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
- ^ Griffin, R. F. (1998). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 142: Xi Ursae Majoris". The Observatory. 118: 273. Bibcode:1998Obs...118..273G.
Cite error: There are <ref group=note> tags on this page, but the references will not show without a {{reflist|group=note}} template (see the help page).