Iota Cassiopeiae
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cassiopeia[1] |
| ι Cas A | |
| Right ascension | 02h 29m 03.960s[2] |
| Declination | +67° 24′ 08.70″[2] |
| Apparent magnitude (V) | 4.61[2] (4.65 / 8.48)[3] |
| ι Cas B | |
| Right ascension | 02h 29m 03.567s[2] |
| Declination | +67° 24′ 07.01″[2] |
| Apparent magnitude (V) | 6.87[2] |
| ι Cas C | |
| Right ascension | 02h 29m 05.086s[2] |
| Declination | +67° 24′ 05.53″[2] |
| Apparent magnitude (V) | 9.05[4] (9.14 / 11.84)[4] |
| Characteristics | |
| U−B color index | +0.03[5] |
| B−V color index | +0.12[5] |
| ι Cas A | |
| Spectral type | A3p / G6[3] |
| Variable type | α2 CVn[6] |
| ι Cas B | |
| Spectral type | F5[3] |
| ι Cas C | |
| Spectral type | K4 / M2[4] |
| U−B color index | +0.18[5] |
| B−V color index | +0.72[5] |
| Astrometry | |
| Radial velocity (Rv) | 1.2±2[7] km/s |
| Proper motion (μ) | RA: −26.61[8] mas/yr[8] Dec.: 38.21 mas/yr[8] |
| Parallax (π) | 22.22±0.08 mas[9] |
| Distance | 146.8 ± 0.5 ly (45.0 ± 0.2 pc) |
| Absolute magnitude (MV) | 1.62±0.07 (Aa) 5.60±0.17 (Ab)[10] |
| Orbit[9] | |
| Primary | ι Cas Aa |
| Name | ι Cas Ab |
| Period (P) | 48.72±0.45 yr |
| Semi-major axis (a) | 0.423±0.004″ |
| Eccentricity (e) | 0.637±0.004 |
| Inclination (i) | 148.2±1.3° |
| Longitude of the node (Ω) | 176.6±1.8° |
| Periastron epoch (T) | B 1993.21±0.05 |
| Argument of periastron (ω) (secondary) | 328.2±1.9° |
| Orbit[9] | |
| Primary | ι Cas A |
| Name | ι Cas B |
| Period (P) | 2,400 yr |
| Semi-major axis (a) | 6.50″ |
| Eccentricity (e) | 0.40 |
| Inclination (i) | 102.9±0.3° |
| Longitude of the node (Ω) | 188.0±0.9° |
| Periastron epoch (T) | B 940±47 |
| Argument of periastron (ω) (secondary) | 113.3±3.4° |
| Details | |
| ι Cas Aa | |
| Mass | 1.98[9] M☉ |
| Radius | 2.3±0.4[11] R☉ |
| Luminosity | 24[11] L☉ |
| Temperature | 8,360±275[11] K |
| Rotation | 1.74033 d[11] |
| Rotational velocity (v sin i) | 48[11] km/s |
| Age | 100[10] Myr |
| ι Cas Ab | |
| Mass | 0.98[9] M☉ |
| ι Cas B | |
| Mass | 1.28[9] M☉ |
| Temperature | 6,540[4] K |
| ι Cas Ca | |
| Temperature | 4,520±20[4] K |
| ι Cas Cb | |
| Temperature | 3,590±45[4] K |
| Other designations | |
| Huagai, BD+66°213, HD 15089, HIP 11569, HR 707, SAO 12298 | |
| ι Cas A: TYC 4058-1504-1 | |
| ι Cas B: TYC 4058-1504-2 | |
| ι Cas C: TYC 4058-1505-1 | |
| Database references | |
| SIMBAD | ι Cas |
| ι Cas A | |
| ι Cas B | |
| ι Cas C | |
Iota Cassiopeiae, also named Huagai,[12] is a multiple star system in the constellation Cassiopeia. Its name is a Bayer designation that is Latinized from ι Cassiopeiae, and abbreviated Iota Cas or ι Cas. The system has a combined apparent magnitude of about 4.5,[6] making it visible to the naked eye. Based on its parallax, it is located about 133 light-years (41 pc) 133 light-years (41 parsecs) from Earth.[8]
Nomenclature
Iota Cassiopeiae, Latinized from ι Cassiopeiae, is the star's Bayer designation. In Chinese astronomy, this star is part of the asterism Huá Gài (華蓋 "Canopy of the Emperor"), which consists of 16 stars, seven forming Huá Gài proper and nine forming Gàng (槓, "Shaft"). The IAU Working Group on Star Names approved the name Huagai for Iota Cassiopeiae Aa on 25 December 2025, and it is now so entered in the IAU Catalog of Star Names. 50 Cassiopeiae was named Gang.[12]
Components
Iota Cassiopeiae is known to be a quintuple star system. The brightest star system, ι Cassiopeiae A, contains a white-colored A-type main-sequence star with a mean apparent magnitude of +4.61.[2] The primary is itself a tighter binary star system. The two stars were resolved by adaptive optics.[3] These are designated Aa and Ab (although confusingly they may also be labeled as A and Aa, respectively).[4] The primary is classified as an Alpha2 Canum Venaticorum-type variable star and the brightness of the system varies from magnitude +4.45 to +4.53 with a period of 1.74 days,[6] because of its magnetic field.[11] The variability in brightness was first detected by Karl D. Rakos in 1962, although its spectrum was known to be variable from earlier observations.[14] The fainter companion is a G-type star with a mass of 0.98 M☉.[9] The orbital period of the system is about 49 years.[9]
| Aa | |||||||||||
| Period: 1.74 d | |||||||||||
| Ab | |||||||||||
| Period: 2,400 y | |||||||||||
| B | |||||||||||
| Separation: ≫ 7″ | |||||||||||
| Ca | |||||||||||
| Separation: 0.20″ | |||||||||||
| Cb | |||||||||||
ι Cassiopeiae B is a yellow-white F-type main sequence dwarf with an apparent magnitude of +6.87.[2] It orbits around ι Cassiopeiae A approximately every 2,400 years with a semi-major axis of around 6.5 arcseconds, but the orbit is not very well constrained.[9] This object may be causing Kozai–Lidov cycles in the inner orbital pair.[9]
ι Cassiopeiae C is itself another binary, designated Ca and Cb,[9] or just C and c.[4] It comprises two stars, a K-type star and an M-type star.[4] It is currently at an angular distance of about 7 arcseconds from the AB pair.[15] Since the semimajor axis of the AB orbit is about 6.5 arcseconds, the true semimajor axis of C's orbit around them is thought to be significantly larger than 7 arcseconds.[9]
References
- ^ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
- ^ a b c d e f g h i j 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.
- ^ a b c d Drummond, Jack; et al. (2003). "ι Cassiopeiae: Orbit, Masses, and Photometry from Adaptive Optics Imaging in the I and H Bands". The Astrophysical Journal. 585 (2): 1007. Bibcode:2003ApJ...585.1007D. doi:10.1086/346224.
- ^ a b c d e f g h i Christou, Julian C.; Drummond, Jack D. (2006). "Measurements of Binary Stars, Including Two New Discoveries, with the Lick Observatory Adaptive Optics System". The Astronomical Journal. 131 (6): 3100. Bibcode:2006AJ....131.3100C. doi:10.1086/503255.
- ^ a b c d Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
- ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
- ^ a b c 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 c d e f g h i j k l Tokovinin, A. (2021). "Inner and Outer Orbits in 13 Resolved Hierarchical Stellar Systems". The Astronomical Journal. 161 (3): 144. arXiv:2101.02976. Bibcode:2021AJ....161..144T. doi:10.3847/1538-3881/abda42. S2CID 231419112.
- ^ a b De Rosa, R. J.; et al. (2012). "The Volume-limited A-Star (VAST) survey - II. Orbital motion monitoring of A-type star multiples". Monthly Notices of the Royal Astronomical Society. 422 (4): 2765. arXiv:1112.3666. Bibcode:2012MNRAS.422.2765D. doi:10.1111/j.1365-2966.2011.20397.x. S2CID 102487103.
- ^ a b c d e f Aurière, M.; et al. (2007). "Weak magnetic fields in Ap/Bp stars". Astronomy and Astrophysics. 475 (3): 1053. arXiv:0710.1554. Bibcode:2007A&A...475.1053A. doi:10.1051/0004-6361:20078189. S2CID 54850596.
- ^ a b "IAU Catalog of Star Names". Retrieved 28 December 2025.
- ^ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
- ^ Rakos, Karl D. (1962). "Photoelectric investigation of magnetic and spectrum variable stars". Bulletin / Lowell Observatory. 5 (12): 227–256. Bibcode:1962LowOB...5..227R. Retrieved 10 October 2024.
- ^ Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series. 124: 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181. (HR 707 Archived 2021-02-05 at the Wayback Machine)