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Theta Cassiopeiae

Location of θ Cassiopeiae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Cassiopeia
Right ascension	01 11 06.16225
Declination	+55° 08′ 59.6472″
Apparent magnitude (V)	4.334
Characteristics
Spectral type	A7 V
U−B color index	+0.130
B−V color index	+0.170
Variable type	Suspected δ Sct
Astrometry
Radial velocity (Rv)	2.5±0.6 km/s
Proper motion (μ)	RA: +226.77 mas/yr Dec.: −18.75 mas/yr
Parallax (π)	24.42 ± 0.24 mas
Distance	134 ± 1 ly (41.0 ± 0.4 pc)
Absolute magnitude (MV)	+1.28
Details
Mass	1.83 M☉
Radius	2.6 R☉
Surface gravity (log g)	4.03±0.14 cgs
Temperature	8,202±279 K
Rotational velocity (v sin i)	103 km/s
Age	650 Myr
Other designations
Marfak, θ Cas, 33 Cassiopeiae, BD+54°236, HD 6961, HIP 5542, HR 343, SAO 22070
Database references
SIMBAD	data

Theta Cassiopeiae or θ Cassiopeiae is a solitary star in the northern constellation of Cassiopeia. It shares the traditional name Marfak /ˈmɑːrfæk/ with μ Cassiopeiae, positioned less than half a degree to the WSW, which is derived from the Arabic term Al Marfik or Al Mirfaq (المرفق), meaning "the elbow". At an apparent visual magnitude of 4.3, Theta Cassiopeiae is visible to the naked eye. Based upon an annual parallax shift of 24.42 mas, it is located about 134 light years from the Sun. It has a total annual proper motion of 0.227 arcseconds per year, and is slowly drifting further away from the Sun with a radial velocity of 2.5 km/s.

In Chinese, 閣道 (Gé Dào), meaning Flying Corridor, refers to an asterism consisting of θ Cassiopeiae, ι Cassiopeiae, ε Cassiopeiae, δ Cassiopeiae, ν Cassiopeiae and ο Cassiopeiae. Consequently, θ Cassiopeiae itself is known as 閣道四 (Gé Dào sì, English: the Fourth Star of Flying Corridor.)

This is an A-type main sequence star with a stellar classification of A7 V. The measured angular diameter of this star is 0.58±0.02 mas, which, at the estimated distance of this star, yields a physical size of about 2.6 times the radius of the Sun. It is about 650 million years in age and is spinning with a projected rotational velocity of 103 km/s. This is a candidate Vega-type system, which means it displays an infrared excess suggesting it has an orbiting debris disk. It is a suspected Delta Scuti variable.

The star appears to be a member of a leading tidal tail of the Hyades cluster.

References

1. ^ 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, S2CID 18759600.
2. ^ Oja, T. (August 1991), "UBV photometry of stars whose positions are accurately known. VI", Astronomy and Astrophysics Supplement Series, 89 (2): 415–419, Bibcode:1991A&AS...89..415O.
3. ^ 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. ^ Frolov, M. S. (April 1970), "List of Probable Delta Scuti Stars", Information Bulletin on Variable Stars, 427: 1, Bibcode:1970IBVS..427....1F.
5. ^ 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, S2CID 59451347, A61.
6. Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal, 116 (1): 284–292, Bibcode:1998AJ....116..284E, doi:10.1086/300413.
7. ^ David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
8. ^ 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:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(41.0\cdot 0.58\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 5.1\cdot R_{\bigodot }\end{aligned}}}$

9. ^ Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
10. "* tet Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-16.
11. Sinnott, Roger W.; Perryman, Michael A. C. (1997), Millennium Star Atlas, vol. 1, Sky Publishing Corporation and the European Space Agency, p. 64, ISBN 0-933346-84-0.
12. Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc., p. 148, ISBN 0-486-21079-0, retrieved 2010-12-12
13. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854, S2CID 2603568.
14. (in Chinese) 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.
15. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
16. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
17. Song, Inseok; et al. (January 2001), "Ages of A-Type Vega-like Stars from uvbyβ Photometry", The Astrophysical Journal, 546 (1): 352–357, arXiv:astro-ph/0010102, Bibcode:2001ApJ...546..352S, doi:10.1086/318269, S2CID 18154947.
18. Röser, Siegfried; et al. (January 2019), "Hyades tidal tails revealed by Gaia DR2", Astronomy & Astrophysics, 621: 5, arXiv:1811.03845, Bibcode:2019A&A...621L...2R, doi:10.1051/0004-6361/201834608, S2CID 118909033, L2.

External links

• Kaler, James B., "Theta Cassiopeiae", Stars, University of Illinois.</ref>

v t e Constellation of Cassiopeia
List of stars in Cassiopeia Cassiopeia in Chinese astronomy
Stars	Bayer α (Schedar) β (Caph) γ (Navi/Tsih) δ (Ruchbah) ε (Segin) ζ (Fulu) η (Achird) θ (Marfak) ι κ λ μ ν ξ ο π ρ σ τ υ υ (Castula) φ χ ψ ω Flamsteed 1 2 4 6 9 10 12 42 47 48 (A) 49 50 54 Variable R S TZ WZ YZ (21) AO AR PZ V373 V509 V547 V669 V705 V762 V863 V773 V987 V1022 V1405 HR 5 91 144 196 244 273 297 743 932 8832 8853 8881 HD 861 7924 7977 15558 17156 (Nushagak) 240210 240237 240429 240430 Other BD+60°2522 Gliese 49 IRAS 23304+6147 LS I +61 303 PSR J0205+6449 Tycho G 4U 0142+61 WR 2 WR 3
Exoplanets HD 7924 b HD 17156 b HD 219134 b c d e (h) f g HD 240210 b HD 240237 b
Star clusters Messier 52 Messier 103 NGC 103 NGC 110 NGC 129 NGC 133 NGC 136 NGC 146 NGC 189 NGC 225 NGC 358 NGC 366 NGC 381 NGC 433 NGC 436 NGC 457 NGC 559 NGC 637 NGC 654 NGC 659 NGC 663 NGC 1027 NGC 7789 NGC 7790 Trumpler 3
Nebulae	NGC 281 7635 Other 3C 58 Cassiopeia A Heart Nebula IC 289 IC 1805 KjPn 8 LBN 114.55+00.22 Sh 2-185 Westerhout 5
Galaxies	NGC 147 185 278 Other Andromeda VII 3C 20 3C 35 Dwingeloo 1 Dwingeloo 2 MB 3 IC 10 Maffei 1 Maffei 2 QSO B0153+744
Astronomical events SN 1181 SN 1572 (B)
Category

• A-type main-sequence stars
• Cassiopeia (constellation)
• Bayer objects
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects
• Stars with proper names