Theta Cassiopeiae

Theta Cassiopeiae
Location of θ Cassiopeiae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cassiopeia
Right ascension 01h 11m 06.16225s[1]
Declination +55° 08′ 59.6472″[1]
Apparent magnitude (V) 4.334[2]
Characteristics
Spectral type A7 V[3]
U−B color index +0.130[2]
B−V color index +0.170[2]
Variable type Suspected δ Sct[4]
Astrometry
Radial velocity (Rv)2.5±0.6[5] km/s
Proper motion (μ) RA: +226.77[1] mas/yr
Dec.: −18.75[1] mas/yr
Parallax (π)24.42 ± 0.24 mas[1]
Distance134 ± 1 ly
(41.0 ± 0.4 pc)
Absolute magnitude (MV)+1.28[6]
Details[7]
Mass1.83 M☉
Radius2.6[8] R☉
Surface gravity (log g)4.03±0.14 cgs
Temperature8,202±279 K
Rotational velocity (v sin i)103[9] km/s
Age650 Myr
Other designations
Marfak, θ Cas, 33 Cassiopeiae, BD+54°236, HD 6961, HIP 5542, HR 343, SAO 22070[10]
Database references
SIMBADdata

Theta Cassiopeiae or θ Cassiopeiae is a solitary[3] 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,[11] which is derived from the Arabic term Al Marfik or Al Mirfaq (المرفق), meaning "the elbow".[12] At an apparent visual magnitude of 4.3,[2] Theta Cassiopeiae is visible to the naked eye. Based upon an annual parallax shift of 24.42 mas,[1] it is located about 134 light years from the Sun. It has a total annual proper motion of 0.227 arcseconds per year,[13] and is slowly drifting further away from the Sun with a radial velocity of 2.5 km/s.[5]

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.[14] Consequently, θ Cassiopeiae itself is known as 閣道四 (Gé Dào sì, English: the Fourth Star of Flying Corridor.)[15]

This is an A-type main sequence star with a stellar classification of A7 V.[3] The measured angular diameter of this star is 0.58±0.02 mas,[16] which, at the estimated distance of this star, yields a physical size of about 2.6 times the radius of the Sun.[8] It is about 650[7] million years in age and is spinning with a projected rotational velocity of 103 km/s.[9] This is a candidate Vega-type system, which means it displays an infrared excess suggesting it has an orbiting debris disk.[17] It is a suspected Delta Scuti variable.[4]

The star appears to be a member of a leading tidal tail of the Hyades cluster.[18]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Oja1991 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Frolov was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Eggen1998 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference David2015 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference lang2006 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Royer2007 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Sinnott_Perryman_1997 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Allen1963 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Lepine2005 was invoked but never defined (see the help page).
  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. ^ Cite error: The named reference Richichi2005 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Song2001 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Röser_et_al_2019 was invoked but never defined (see the help page).