Theta Cassiopeiae
 Location of θ Cassiopeiae (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 01h 11m 06.16225s |
| 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 ± 0.24mas |
| Distance | 134 ± 1 ly (41.0 ± 0.4 pc) |
| 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 | |
| Database references | |
| SIMBAD | data |
Theta Cassiopeiae (θ Cas, θ Cassiopeiae) is a solitarystar in the northern constellation of Cassiopeia. It shares the traditional name Marfark or Marfak with μ Cassiopeiae to the southeast, which is derived from the Arabic term Al Marfik or Al Mirfaq (المرفق), meaning "the elbow". At an apparent visual magnitude of 4.3, it 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.
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.
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