Upsilon² Eridani

υ² Eridani
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	04h 35m 33.03834s
Declination	−30° 33′ 44.4297″
Apparent magnitude (V)	3.804
Characteristics
Spectral type	G8+ III
U−B color index	+0.740
B−V color index	+0.968
Astrometry
Radial velocity (Rv)	−4.0±0.9 km/s
Proper motion (μ)	RA: −49.27 mas/yr ; Dec.: −12.72 mas/yr
Parallax (π)	15.25 ± 0.19 mas
Distance	214 ± 3 ly ; (65.6 ± 0.8 pc)
Details
Radius	16 R☉
Luminosity	138 L☉
Surface gravity (log g)	2.77±0.07 cgs
Temperature	5,074±30 K
Metallicity [Fe/H]	0.04±0.03 dex
Other designations
	Theemim, Theemin, Beemin, υ2 Eri, Upsilon2 Eridani, Upsilon2 Eri, 52 Eridani, 52 Eri, CD −30° 1901, CPD−30 631, FK5 170, GC 5614, HD 29291, HIP 21393, HR 1464, PPM 280424, SAO 195148.
Database references
SIMBAD	data

Upsilon² Eridani (Upsilon² Eri, υ² Eridani, υ² Eri) is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.8^[2] Based upon an annual parallax shift of 0.01525″,^[1] it is approximately 214 light-years from the Sun.

In Chinese, 天園 (Tiān Yuán), meaning Celestial Orchard, refers to an asterism consisting of υ² Eridani, χ Eridani, φ Eridani, κ Eridani, HD 16754, HD 23319, θ Eridani, HD 24072, HD 24160, υ⁴ Eridani, 43 Eridani and υ¹ Eridani.^[9] Consequently, υ² Eridani itself is known as 天園十二 (Tiān Yuán shíèr, Template:Lang-en.)^[10]

This is a evolved red clump^[11] giant star with a stellar classification of G8+ III.^[3] The measured angular diameter is 2.21 mas.^[12] At an estimated distance of the star, this yields a physical size of around 16 times the radius of the Sun.^[5] It radiates 138^[6] times the solar luminosity from its outer atmosphere at an effective temperature of 5074 K.^[7]

References

^ ^a ^b ^c ^d ^e ^f van Leeuwen, F. (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.
^ ^a ^b ^c ^d Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, vol. 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G.
^ ^a ^b Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
^ ^a ^b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(65.6\cdot 2.21\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 31.2\cdot R_{\bigodot }\end{aligned}}$
^ ^a ^b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.{{citation}}: CS1 maint: unflagged free DOI (link)
^ ^a ^b ^c ^d Alves, S.; et al. (April 2015), "Determination of the spectroscopic stellar parameters for 257 field giant stars", Monthly Notices of the Royal Astronomical Society, 448 (3): 2749−2765, arXiv:1503.02556, Bibcode:2015MNRAS.448.2749A, doi:10.1093/mnras/stv189.{{citation}}: CS1 maint: unflagged free DOI (link)
^ "ups02 Eri -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13.
^ Template:Zh icon 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
^ Template:Zh icon 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
^ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278.
^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.

[vanLeeuwen2007-1] ^ ^a ^b ^c ^d ^e ^f van Leeuwen, F. (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.

[Gutierrez-Moreno1966-2] Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, vol. 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G.

[Keenan1989-3] Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.

[deBruijne2012-4] Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.

[lang2006-5] Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(65.6\cdot 2.21\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 31.2\cdot R_{\bigodot }\end{aligned}}$

[Mcdonald2012-6] McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.{{citation}}: CS1 maint: unflagged free DOI (link)

[Alves2015-7] Alves, S.; et al. (April 2015), "Determination of the spectroscopic stellar parameters for 257 field giant stars", Monthly Notices of the Royal Astronomical Society, 448 (3): 2749−2765, arXiv:1503.02556, Bibcode:2015MNRAS.448.2749A, doi:10.1093/mnras/stv189.{{citation}}: CS1 maint: unflagged free DOI (link)

[SIMBAD-8] "ups02 Eri -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13.

[9] Template:Zh icon 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.

[10] Template:Zh icon 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.

[Alves2000-11] Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278.

[Richichi2005-12] Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.

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Observation data Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	04^h 35^m 33.03834^s^[1]
Declination	−30° 33′ 44.4297″^[1]
Apparent magnitude (V)	3.804^[2]
Characteristics
Spectral type	G8+ III^[3]
U−B color index	+0.740^[2]
B−V color index	+0.968^[2]
Astrometry

Radial velocity (R_v)	−4.0±0.9^[4] km/s
Proper motion (μ)	RA: −49.27^[1] mas/yr Dec.: −12.72^[1] mas/yr
Parallax (π)	15.25 ± 0.19 mas^[1]
Distance	214 ± 3 ly (65.6 ± 0.8 pc)

Details

Radius	16^[5] `R`_☉
Luminosity	138^[6] `L`_☉
Surface gravity (log g)	2.77±0.07^[7] cgs
Temperature	5,074±30^[7] K
Metallicity [Fe/H]	0.04±0.03^[7] dex

Other designations
Theemim, Theemin, Beemin, υ² Eri, Upsilon² Eridani, Upsilon² Eri, 52 Eridani, 52 Eri, CD −30° 1901, CPD−30 631, FK5 170, GC 5614, HD 29291, HIP 21393, HR 1464, PPM 280424, SAO 195148.^[8]
Database references
SIMBAD	data