Upsilon2 Cassiopeiae

υ² Cassiopeiae

Template:Location mark Location of υ2 Cassiopeiae (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cassiopeia
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	+4.62
Characteristics
Evolutionary stage	horizontal branch
Spectral type	G8 IIIb Fe−0.5
U−B Template:Engvar	+0.68
B−V Template:Engvar	+0.96
Astrometry
Radial velocity (Rv)	Template:Val km/s
Proper motion (μ)	RA: −92.085 mas/yr Dec.: −45.079 mas/yr
Parallax (π)	17.2875±0.1880 mas
Distance	Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)	+0.62
Details
Mass	Template:Val Template:Solar mass
Radius	Template:Val Template:Solar radius
Luminosity	Template:Val Template:Solar luminosity
Surface gravity (log g)	Template:Val cgs
Temperature	Template:Val K
Metallicity [Fe/H]	Template:Val dex
Rotational velocity (v sin i)	Template:Val km/s
Age	Template:Val Gyr
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
Castula, Template:Odlist
Database references
SIMBAD	data

Upsilon² Cassiopeiae is a solitary star in the constellation of Cassiopeia, a few degrees to the south of Gamma Cassiopeiae. It has the proper name Castula Template:IPAc-en, which has been officially adopted by the IAU. The star has a yellow hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.62. Based upon parallax measurements, it is located at a distance of approximately 189 light years from the Sun. The star is drifting closer with a radial velocity of −48 km/s.

This is an aging giant star with a stellar classification of G8 IIIb Fe−0.5, where the suffix notation indicates a mild underabundance of iron in the spectrum. With the supply of core hydrogen exhausted, this star has cooled and expanded off the main sequence – at present it has 10 times the girth of the Sun. It is a red clump giant, which means it is on the horizontal branch undergoing core helium fusion.

Upsilon² Cassiopeiae is a barium star, showing an excess of the element barium in its spectrum. This can occur from mass transfer from a more-evolved companion star that later became a white dwarf, although no companion has been detected. It is 2.2 billion years old with 1.44 times the mass of the Sun. The star is radiating 55 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,937 K.

Nomenclature

Upsilon² Cassiopeiae, Latinised from υ² Cassiopeiae, is the star's Bayer designation.

This star bore the name Castula in Bayer's Uranometria, which is Latin for a type of woman's tunic. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Castula for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.