21 Arietis

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21 Arietis
Observation data
Epoch J2000       Equinox J2000
Constellation Aries
Right ascension 02h 15m 42.77662s [1]
Declination +25° 02′ 34.9627″ [1]
Apparent magnitude  (V)5.57 [2] (6.40/6.48) [3]
Characteristics
Spectral type F6 V [4]
U−B color index +0.00 [5]
B−V color index +0.50 [5]
Astrometry
Radial velocity (Rv)−44.3 km/s
Proper motion (μ)RA: −89.72 [1]   mas/yr
Dec.: −86.42 [1]   mas/yr
Parallax (π)19.58 ± 0.61  mas [1]
Distance 167 ± 5  ly
(51 ± 2  pc)
Absolute magnitude  (MV)2.03 [2]
Orbit [6]
Period (P)23.70 ± 0.12 yr
Semi-major axis (a)0.2353 ± 0.0011″
Eccentricity (e)0.6816 ± 0.0037
Inclination (i)104.52 ± 0.16°
Longitude of the node (Ω)236.44 ± 0.22°
Periastron epoch (T)1986.192 ± 0.012
Argument of periastron (ω)
(secondary)		84.16 ± 0.16°
Details
21 Ari A
Mass 1.338 ± 0.032 [7]   M☉
Surface gravity (log g)4.12 [8]   cgs
Temperature 6,299 [8]   K
Metallicity [Fe/H]+0.02 [8]   dex
Rotational velocity (v sin i)12.6 [9]  km/s
Age 2.2 [2]   Gyr
21 Ari B
Mass 1.374 ± 0.027 [7]   M☉
Other designations
BD+24 329, FK5 1059, HD 13872, HIP 10535, HR 657, SAO 75238, WDS J02157+2503. [5]
Database references
SIMBAD data

21 Arietis (abbreviated 21 Ari) is a binary star [3] system in the northern constellation of Aries. 21 Arietis is the Flamsteed designation. It has a combined apparent visual magnitude is 5.57; [2] the brighter member is magnitude 6.40 while the fainter star is magnitude 6.48. [3] The distance to this star system, based upon an annual parallax shift of 19.58  mas, [1] is 167 light-years (51 parsecs ). The pair orbit each other with a period of 23.70 years and an eccentricity of 0.68. [3]

The system was initially thought to be a triple system in 1981, since the orbit of the system predicted a mass greater than would be expected from its F6V spectral type. [10] This was later rejected because the distance to the system was overestimated. However, while observing the spectrum of the system, it was found that a giant planet may be causing radial velocity variations. The purported planet would have a mass of 1.40 ± 0.36 MJ, an orbital period of 925 days and orbit the primary star. [7]

Related Research Articles

<span class="mw-page-title-main">Gamma Arietis</span> Star in the constellation Aries

Gamma Arietis is a binary star in the northern constellation of Aries. The two components are designated γ1 Arietis or Gamma Arietis B and γ2 Arietis or Gamma Arietis A. γ1 Arietis may itself be a spectroscopic binary with a low mass companion.

<span class="mw-page-title-main">Omega Ursae Majoris</span> Binary system in the constellation Ursa Major

Omega Ursae Majoris is the Bayer designation for a binary star system in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye with an apparent visual magnitude of 4.61. Based upon an annual parallax shift of 13.24 mas, it is roughly 246 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.11 due to interstellar dust.

<span class="mw-page-title-main">Epsilon Arietis</span> Binary star system in the constellation Aries

Epsilon Arietis is the Bayer designation for a visual binary star system in the northern constellation of Aries. It has a combined apparent visual magnitude of 4.63 and can be seen with the naked eye, although the two components are too close together to be resolved without a telescope. With an annual parallax shift of 9.81 mas, the distance to this system can be estimated as 330 light-years, give or take a 30 light-year margin of error. It is located behind the dark cloud MBM12.

<span class="mw-page-title-main">Kappa Arietis</span> Binary star system in the constellation Aries

Kappa Arietis, Latinized from κ Arietis, is the Bayer designation for a binary star in the northern constellation of Aries. The combined apparent visual magnitude of the pair is 5.02, making the system bright enough for it to be dimly visible to the naked eye as a white-hued point of light. It is located approximately 181 light-years from the Sun based on parallax, and is drifting further away with a radial velocity of +11.5 km/s.

<span class="mw-page-title-main">Theta Arietis</span> Binary star system in the constellation Aries

Theta Arietis, Latinised from θ Arietis, is the Bayer designation for a binary star system in the northern constellation of Aries. It is faintly visible to the naked eye with an apparent visual magnitude of 5.58. With an annual parallax shift of 7.61 mas, the distance to this star is an estimated 429 light-years with a 10-light-year margin of error. It is drifting further away with a radial velocity of +6 km/s.

<span class="mw-page-title-main">Mu Arietis</span> Star system in the constellation Aries

Mu Arietis, Latinized from μ Arietis, is the Bayer designation for a star system in the northern constellation of Aries. It is approximately 340 light-years distant from Earth, give or take a 30 light-year margin of error, and has a combined apparent visual magnitude of 5.74. According to the Bortle Dark-Sky Scale, this means it is faintly visible to the naked eye from dark suburban skies.

36 Andromedae is a visual binary star system in the northern constellation of Andromeda. The designation is from the star catalogue of English astronomer John Flamsteed, first published in 1712. It is faintly visible to the naked eye with an apparent visual magnitude of 5.45. An annual parallax shift of 26.33 mas yields a distance estimate of about 124 light years. The system is moving closer to the Sun with a radial velocity of −0.8 km/s.

<span class="mw-page-title-main">35 Arietis</span> Star in the constellation Aries

35 Arietis is a binary star in the northern constellation of Aries. 35 Arietis is the Flamsteed designation. It is approximately 340 light-years distant from the Earth, based upon an annual parallax shift of 9.51 mas. This star is visible to the naked eye with an apparent visual magnitude of 4.64.

31 Arietis is a binary star in the northern constellation of Aries. 31 Arietis is the Flamsteed designation. The two members of this system orbit each other with a period of 3.80 years and an eccentricity of 0.017. Both components of the system are F-type main sequence stars with a stellar classification of F7 V. The pair have an apparent visual magnitude of 5.75, which is just bright enough to be faintly visible to the naked eye. Based upon an annual parallax shift of 28.79 mas, the distance to this system is approximately 113 light-years. The system is located near the ecliptic, so it is subject to occultation by the Moon. The dynamical mass of the system is 3.36 ± 0.04 M☉.

10 Arietis is a binary star system in the northern constellation of Aries. 10 Arietis is the Flamsteed designation. It is visible to the naked eye as a dim, yellow-white hued star with a combined apparent visual magnitude of 5.63. Based upon parallax measurements, it is located around 159 light years away from the Sun. The system is receding from the Earth with a heliocentric radial velocity of +12.9 km/s.

7 Arietis is a binary star system in the northern constellation of Aries. 7 Arietis is the Flamsteed designation. The pair have a combined apparent visual magnitude of 5.76, making it faintly visible to the naked eye from dark suburban skies. Based upon an annual parallax shift of 5.39 mas, it is approximately 600 light-years distant from the Earth, give or take a 30 light-year margin of error. It is drifting further away from the Sun with a radial velocity of +16 km/s.

<span class="mw-page-title-main">30 Arietis</span> Multiple star system in the constellation Aries

30 Arietis is a 6th-apparent-magnitude multiple star system in the constellation of Aries. 30 Arietis is the Flamsteed designation. 30 Arietis A and B are separated by 38.1″ or about 1,500 AU at a distance of 130 light years away. The main components of both systems are both binaries with a composite spectra belonging to F-type main-sequence stars, meaning they are fusing hydrogen in their cores. The 30 Arietis system is 910 million years old, one fifth the age of the Sun.

<span class="mw-page-title-main">23 Vulpeculae</span> Star in the constellation Vulpecula

23 Vulpeculae is a triple star system in the northern constellation of Vulpecula. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.52 and it is located approximately 327 light years away from the Sun based on parallax. The system is moving further from the Earth with a heliocentric radial velocity of +1.47 km/s.

HD 6114 is a visual binary star system in the northern constellation of Andromeda. With a combined apparent magnitude of 6.46, the star can only be seen with the naked eye by keen-eyed observers even on the best of nights. Based upon an annual parallax shift of 10.4 mas as seen from Earth's orbit, the system is located approximately 108 parsecs (350 ly) distant.

Rho3 Arietis is the Bayer designation for a star in the northern constellation of Aries. It is faintly visible to the naked eye with an apparent visual magnitude of 5.63. Based upon an annual parallax shift of 28.29 mas, this star is located at a distance of approximately 115 light-years from Earth.

45 Aquilae, abbreviated 45 Aql, is a triple star system in the equatorial constellation of Aquila. 45 Aquilae is its Flamsteed designation. It is located 350 light-years away from Earth, give or take a 6 light-year margin of error, and has a combined apparent visual magnitude of 5.7. The system is moving closer to the Earth with a heliocentric radial velocity of -46 km/s.

29 Arietis is a triple star system in the northern constellation of Aries. 29 Arietis is the Flamsteed designation. Its annual parallax shift of 34.86±0.13 mas indicates a distance of about 94 light-years from Earth. The system is barely visible to the naked eye with an apparent visual magnitude of 6.0; it is 0.02 degree north of the ecliptic. It is moving further from Earth with a heliocentric radial velocity of 9 km/s.

<span class="mw-page-title-main">UX Arietis</span> Trinary star system in the constellation Aries

UX Arietis is a triple star system located in the northern zodiacal constellation of Aries. Based upon parallax measurements from the Gaia satellite, it is roughly 165 light years away. The primary, component Aa, is a variable star of the RS CVn type. The variability of the star is believed due to a combination of cool star spots and warm flares, set against the baseline quiescent temperature of the stellar atmosphere. The variability appears to be cyclical with a period of 8−9 years. The star varies in brightness from magnitude 6.35 to 6.71, meaning it may be intermittently visible to the unaided eye under ideal dark-sky conditions.

<span class="mw-page-title-main">Kappa Fornacis</span> Star system in the constellation Fornax

Kappa Fornacis is a star system that lies approximately 72 light-years away. The system consists of a somewhat evolved primary orbited by a massive, 'dark' secondary that is actually itself a close red dwarf binary, making a hierarchal triple system.

λ Librae is the Bayer designation for a binary star system in the zodiac constellation of Libra. It can be faintly seen with the naked eye, having an apparent visual magnitude of 5.03. With an annual parallax shift of 10.54 mas, it is roughly 310 light years from the Sun. At that distance, the visual magnitude of this system is diminished by an extinction factor of 0.22 due to interstellar dust. It is 0.1 degree north of the ecliptic.

References

  1. 1 2 3 4 5 6 van Leeuwen, F. (November 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.
  2. 1 2 3 4 Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv: 0811.3982 , Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID   118577511.
  3. 1 2 3 4 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society , 389 (2): 869–879, arXiv: 0806.2878 , Bibcode:2008MNRAS.389..869E, doi: 10.1111/j.1365-2966.2008.13596.x , S2CID   14878976.
  4. ↑ Harlan, E. A. (September 1969), "MK classifications for F- and G-type stars. I", Astronomical Journal, 74: 916–919, Bibcode:1969AJ.....74..916H, doi:10.1086/110881.
  5. 1 2 3 "* 21 Ari". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2012-07-18.
  6. ↑ Hartkopf, William I.; Mason, Brian D.; McAlister, Harold A. (January 1996), "Binary Star Orbits From Speckle Interferometry. VIII. Orbits of 37 Close Visual System", Astronomical Journal, 111: 370, Bibcode:1996AJ....111..370H, doi: 10.1086/117790 .
  7. 1 2 3 Muterspaugh, Matthew W.; Lane, Benjamin F.; Kulkarni, S. R.; Konacki, Maciej; Burke, Bernard F.; Colavita, M. M.; Shao, M.; Hartkopf, William I.; Boss, Alan P.; Williamson, M. (2010). "The Phases Differential Astrometry Data Archive. V. Candidate Substellar Companions to Binary Systems". The Astronomical Journal. 140 (6): 1657. arXiv: 1010.4048 . Bibcode:2010AJ....140.1657M. doi:10.1088/0004-6256/140/6/1657. S2CID   59585356.
  8. 1 2 3 Balachandran, Suchitra (May 1, 1990), "Lithium depletion and rotation in main-sequence stars", Astrophysical Journal, Part 1, 354: 310–332, Bibcode:1990ApJ...354..310B, doi:10.1086/168691.
  9. ↑ Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi: 10.1051/0004-6361:200810377 [ permanent dead link ]
  10. ↑ Couteau, P.; Morel, P. J. (1982). "Is 21 Ari = Cou 79 a multiple system?". Astronomy and Astrophysics. 105: 323. Bibcode:1982A&A...105..323C.


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