  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 17h 05m 20.12403s[1] |
| Declination | +54° 28′ 12.0994″[1] |
| Apparent magnitude (V) | 4.92[2] (5.66 / 5.69)[3] |
| Characteristics | |
| Spectral type | F7V |
| U−B color index | −0.01[4] |
| B−V color index | +0.47[4] |
| Astrometry | |
| Radial velocity (Rv) | −17.30 ± 0.5[5] km/s |
| Proper motion (μ) | RA: −58.16[1] mas/yr Dec.: 67.87[1] mas/yr |
| Parallax (π) | 36.45 ± 0.46 mas[1] |
| Distance | 89 ± 1 ly (27.4 ± 0.3 pc) |
| Absolute magnitude (MV) | +2.73[6] |
| Orbit[3] | |
| Primary | μ Dra A |
| Companion | μ Dra B |
| Period (P) | 812.0 ± 70.5 yr |
| Semi-major axis (a) | 4.48 ± 0.03″ |
| Eccentricity (e) | 0.5139 ± 0.029 |
| Inclination (i) | 142.2 ± 1.3° |
| Longitude of the node (Ω) | 282.85 ± 0.80° |
| Periastron epoch (T) | 1946.19 ± 0.72 |
| Argument of periastron (ω) (secondary) | 193.31 ± 0.083° |
| Details | |
| μ Dra A | |
| Mass | 1.35[7] M☉ |
| Metallicity [Fe/H] | −0.01[6] dex |
| μ Dra B | |
| Mass | 1.30[7] M☉ |
| Age | 2.2[6] Gyr |
| Other designations | |
| A: Alrakis, HR 6370, HD 154906 | |
| B: HR 6369, HD 154905 | |
| Database references | |
| SIMBAD | μ Dra |
| μ Dra A | |
| μ Dra B | |
Mu Draconis (μ Draconis, abbreviated Mu Dra, μ Dra) is a multiple star system near the head of the constellation of Draco. With a combined magnitude of 4.92,[2] it is visible to the naked eye. Based on parallax estimates by the Hipparcos spacecraft, it is located approximately 89 light-years from the Sun.[1]
The system consists of a single primary star (designated Mu Draconis A, officially named Alrakis /ælˈreɪkɪs/ from the traditional name of the system),[8][9] a secondary binary pair (Mu Draconis B) and a further single star (C). B's two components are designated Mu Draconis Ba and Bb.
Mu Draconis A and Ba are nearly identical F-type main-sequence stars, with masses of 1.35 M☉ and 1.30 M☉, respectively.[7] Both have the spectral class of F5V, and have similar apparent magnitude, at 5.66 and 5.69, respectively.[3] The secondary, Mu Draconis B, has a drifting radial velocity, and is itself a spectroscopic binary with an orbital period of 2,270 days.[10] The distance between both stars is 2 arcseconds, so a telescope with a diameter of at least 6 centimetres is necessary to see them separate. The smaller component, Mu Draconis Bb, has a mass of 0.2 M☉. Mu Draconis C is a 14th magnitude common-proper-motion companion 13.2" away from the bright pair, with a mass of 0.29 M☉.[7]
- ^ a b c d e f van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b "* mu Dra". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 May 2017.
- ^ a b c "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 16 May 2017.
- ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data: 0. Bibcode:1986EgUBV........0M.
- ^ Holmberg, J.; Nordström, B.; Andersen, J. (2007). "The Geneva-Copenhagen survey of the Solar neighbourhood II". Astronomy and Astrophysics. 475 (2): 519. arXiv:0707.1891. Bibcode:2007A&A...475..519H. doi:10.1051/0004-6361:20077221. S2CID 119054949.
- ^ a b c Holmberg, J.; Nordström, B.; Andersen, J. (2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics. 501 (3): 941. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. S2CID 118577511.
- ^ a b c d Tokovinin, Andrei (2014). "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs". The Astronomical Journal. 147 (4): 87. arXiv:1401.6827. Bibcode:2014AJ....147...87T. doi:10.1088/0004-6256/147/4/87. S2CID 56066740.
- ^ 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.
- ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.
- ^ Pourbaix, D.; et al. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088. (SB9 catalog entry)