Theta Cassiopeiae

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title: "Theta Cassiopeiae" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["a-type-main-sequence-stars", "cassiopeia-(constellation)", "bayer-objects", "bright-star-catalogue-objects", "durchmusterung-objects", "flamsteed-objects", "henry-draper-catalogue-objects", "hipparcos-objects", "stars-with-proper-names"] description: "Star in the constellation Cassiopeia" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Theta_Cassiopeiae" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Star in the constellation Cassiopeia ::

| image = | image=Cassiopeia_IAU.svg | float=center | width=240 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=θ Cas | x%=47.1 | y%=59.4 | caption=Location of θ Cassiopeiae (circled) | epoch = J2000.0 | equinox = J2000.0 (ICRS) | constell = Cassiopeia | ra = | dec = | appmag_v = 4.334 | type = main sequence | class = A7 V | b-v = +0.170 | u-b = +0.130 | r-i = | variable = Suspected δ Sct | radial_v = | prop_mo_ra = +226.056 | prop_mo_dec = −19.541 | pm_footnote = | parallax = 23.8844 | p_error = 0.1136 | parallax_footnote = | absmag_v = +1.28 | source = | mass = 1.9 | radius = 2.5 | luminosity = 23 | temperature = 7,954 | gravity = 3.91 | metal_fe = +0.07 | rotational_velocity = 103 | age_myr = 650 | names = | Simbad = tet+Cas

Theta Cassiopeiae is a solitary star in the northern constellation of Cassiopeia. Its name is a Bayer designation that is Latinized from θ Cassiopeiae, and abbreviated Theta Cas or θ Cas. It shares the traditional name Marfak 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 , it is located 136.6 ly 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, .)

This is an A-type main sequence star with a stellar classification of A7 V. The star has 1.9 times the Sun's mass and 2.5 times the Sun's radius. It is about 650 million years in age and is spinning with a projected rotational velocity of 103 km/s. The star is radiating 23 times the luminosity of the Sun from its photosphere at an effective temperature of 7,954 K. 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

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| title=* tet Cas | accessdate=2017-02-16 }}

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