Alpha Equulei
Location of α Equulei (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Equuleus |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | +3.919[2] (4.476 + 4.496)[3] |
| Characteristics | |
| Spectral type | G7III + kA3hA4mA9[4] |
| U−B color index | +0.284[2] |
| B−V color index | +0.529[2] |
| Astrometry | |
| Radial velocity (Rv) | −16.458±0.027[5] km/s |
| Proper motion (μ) | RA: +49.747 mas/yr[1] Dec.: −89.846 mas/yr[1] |
| Parallax (π) | 18.11±0.24 mas[5] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute magnitude (MV) | +0.146 (0.689 + 1.159)[3] |
| Orbit[5] | |
| Period (P) | 98.80450±0.00035 days |
| Semi-major axis (a) | 0.66±0.02 au[3] |
| Eccentricity (e) | 0.00417±0.00076 |
| Inclination (i) | 151.52±0.28° |
| Longitude of the node (Ω) | 216.57±0.16° |
| Periastron epoch (T) | 2,457,277.7±1.7 |
| Argument of periastron (ω) (primary) | 102.9±6.3° |
| Semi-amplitude (K1) (primary) | 16.190±0.036 km/s |
| Semi-amplitude (K2) (secondary) | 18.92±0.61 km/s |
| Details | |
| A | |
| Mass | 2.20±0.16[5] M☉ |
| Radius | 9.20±0.01[6] R☉ |
| Luminosity | 47.9+12.4 −9.8[3] L☉ |
| Surface gravity (log g) | 3.08±0.11[5] cgs |
| Temperature | 5,160±65[6] K |
| Metallicity [Fe/H] | +0.11±0.06[6] dex |
| Rotational velocity (v sin i) | 5.53±0.14[6] km/s |
| Age | 1.0–1.2[5] Gyr |
| B | |
| Mass | 1.883±0.083[5] M☉ |
| Radius | 2.60±0.03[6] R☉ |
| Luminosity | 26.9+3.3 −2.9[3] L☉ |
| Surface gravity (log g) | 3.87±0.15[5] cgs |
| Temperature | 8,260±218[6] K |
| Metallicity [Fe/H] | +0.14±0.16[6] dex |
| Rotational velocity (v sin i) | 25.88±3.45[6] km/s |
| Age | 1.0–1.2[5] Gyr |
| Other designations | |
| Kitalphar, 8 Equulei, HR 8131, HD 202447, BD+04 4635, HIP 104987, SAO 126662, FK5 800, GC 29735 | |
| Database references | |
| SIMBAD | data |
Alpha Equulei (α Equulei, abbreviated Alpha Equ, α Equ), officially named Kitalpha /kɪˈtælfə/,[7][8] is the brightest star in the constellation of Equuleus. It is a binary system with an orbital period of 98.8 days and a sky separation of a few milliarcseconds, too small to be resolved with the naked eye.
Nomenclature
α Equulei (Latinised to Alpha Equulei) is the star's Bayer designation.
It bore the traditional name Kitalpha (rarely Kitel Phard or Kitalphar), a contraction of the Arabic name قطعة الفرس qiṭ‘a(t) al-faras—"a piece of the horse". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[9] to catalogue and standardize proper names for stars. The WGSN approved the name Kitalpha for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[8]
In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Emptiness, is an asterism consisting of Alpha Equulei and Beta Aquarii.[10] Consequently, the Chinese name for Alpha Equulei itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[11]
Properties
The overall appearance of α Equulei is a G-type giant[12] with an apparent magnitude of +3.92,[2] but it is a spectroscopic binary consisting of two individual stars.[6]
The primary star is a G7 giant about fifty times more luminous than the Sun.[3] It has an effective temperature of 5,160 K and a radius of 9.2 times greater than the Sun.[6]
The secondary is an A-type main-sequence star that is about 27 times as luminous as the Sun.[3] It has an effective temperature of 8,260 K and a radius 2.60 times greater than the Sun. It is a chemically peculiar Am star.[4][6]
The two stars revolve in a circular orbit every 98.8 days. Their respective orbital velocities allow their masses to be calculated at 2.3 M☉ and 2.0 M☉, respectively.[4]
References
- ^ a b c Template:Cite DR3
- ^ a b c d Page Module:Citation/CS1/styles.css has no content.Cousins, A. W. J. (1984). "Standardization of Broadband Photometry of Equatorial Standards". South African Astronomical Observatory Circulars. 8: 59. Bibcode:1984SAAOC...8...59C.
- ^ a b c d e f g Page Module:Citation/CS1/styles.css has no content.Piccotti, Luca; Docobo, José Ángel; Carini, Roberta; Tamazian, Vakhtang S.; Brocato, Enzo; Andrade, Manuel; Campo, Pedro P. (2020-02-01). "A study of the physical properties of SB2s with both the visual and spectroscopic orbits". Monthly Notices of the Royal Astronomical Society. 492 (2): 2709–2721. Bibcode:2020MNRAS.492.2709P. doi:10.1093/mnras/stz3616. ISSN 0035-8711.
- ^ a b c Page Module:Citation/CS1/styles.css has no content.Griffin, R. E. M.; Griffin, R. F. (2002). "Composite spectra Paper 11: α Equulei, an astrometric binary with an Am secondary". Monthly Notices of the Royal Astronomical Society. 330 (2): 288. Bibcode:2002MNRAS.330..288G. doi:10.1046/j.1365-8711.2002.05030.x.
- ^ a b c d e f g h i Page Module:Citation/CS1/styles.css has no content.Halbwachs, J-L; Kiefer, F; Lebreton, Y; Boffin, H M J; Arenou, F; Le Bouquin, J-B; Famaey, B; Pourbaix, D; Guillout, P; Salomon, J-B; Mazeh, T (2020-08-01). "Masses of the components of SB2 binaries observed with Gaia – V. Accurate SB2 orbits for 10 binaries and masses of the components of 5 binaries". Monthly Notices of the Royal Astronomical Society. 496 (2): 1355–1368. doi:10.1093/mnras/staa1571. ISSN 0035-8711.
- ^ a b c d e f g h i j k Page Module:Citation/CS1/styles.css has no content.Romanovskaya, Anna; Zvyagintsev, Sergey (2025-08-06). "Abundance Analysis of the Spectroscopic Binary α Equulei". Galaxies. 13 (4): 88. Bibcode:2025Galax..13...88R. doi:10.3390/galaxies13040088. ISSN 2075-4434.
- ^ Page Module:Citation/CS1/styles.css has no content.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 Page Module:Citation/CS1/styles.css has no content."IAU Catalog of Star Names". Retrieved 28 July 2016.
- ^ Page Module:Citation/CS1/styles.css has no content."IAU Working Group on Star Names (WGSN)". International Astronomical Union. Archived from the original on 10 June 2016. Retrieved 22 May 2016.
- ^ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
- ^ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Script error: No such module "webarchive"., Hong Kong Space Museum. Accessed on line November 23, 2010.
- ^ Page Module:Citation/CS1/styles.css has no content.Ginestet, N.; Carquillat, J. M.; Jaschek, C. (1999). "Spectral classifications in the near infrared of stars with composite spectra. III. Study of a sample of 137 objects with the Aurelie spectrograph". Astronomy and Astrophysics Supplement. 134 (3): 473. Bibcode:1999A&AS..134..473G. doi:10.1051/aas:1999444.
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