Beta Arietis

β Arietis

Template:Location mark Location of β Arietis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Aries
Right ascension	Template:RA
Declination	Template:DEC
Apparent magnitude (V)	2.655 (2.712 + 5.789)
Characteristics
Spectral type	A3V + G2V
U−B Template:Engvar	+0.170
B−V Template:Engvar	+0.142
Astrometry
Radial velocity (Rv)	−1.9±0.9 km/s
Proper motion (μ)	RA: +98.74 mas/yr Dec.: −110.41 mas/yr
Parallax (π)	55.827±0.308 mas
Distance	Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)	1.382 (1.444 + 4.521)
Details
A
Mass	Template:Val Template:Solar mass
Radius	Template:Solar radius calculatorTemplate:Efn Template:Solar radius
Luminosity	Template:Val Template:Solar luminosity
Surface gravity (log g)	4.0 cgs
Temperature	8,759 K
Metallicity [Fe/H]	0.16 dex
Rotational velocity (v sin i)	73 km/s
Age	Template:Val Myr
B
Mass	Template:Val Template:Solar mass
Radius	Template:Solar radius calculatorTemplate:Efn Template:Solar radius
Luminosity	Template:Val Template:Solar luminosity
Temperature	5,811 K
Metallicity [Fe/H]	{{{metal_fe2}}} dex
Other designations
Template:Odlist
Database references
SIMBAD	data
ARICNS	data

Beta Arietis is a binary star system in the constellation of Aries, marking the ram's second horn. Its identifier is a Bayer designation that is Latinized from β Arietis, and abbreviated Beta Ari or β Ari. It has the official name Sheratan, pronounced Template:IPAc-en. This system is visible to the naked eye as a point of light with a combined apparent visual magnitude of 2.65, making this the second-brightest star in the constellation. Located at a distance of Template:Convert, the pair orbit each other with a period of 107 days.

Nomenclature

Beta Arietis is the star's Bayer designation. It also bears the Flamsteed designation 6 Arietis.

The traditional name, Sheratan (or Sharatan, Sheratim), in full Al Sharatan, is from the Arabic الشرطان aš-šaraţān "the two signs", a reference to the star having marked the northern vernal equinox together with Gamma Arietis several thousand years ago. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Sheratan for this star on August 21, 2016 and it is now so entered in the IAU Catalog of Star Names.

In Chinese, (), meaning Bond (asterism), refers to an asterism consisting of β Arietis, γ Arietis and α Arietis. Consequently, the Chinese name for β Arietis itself is (, Template:Langx).

Properties

Beta Arietis has an apparent visual magnitude of 2.65. Based on dynamical parallax measurements, it is located at a distance of Template:Convert from Earth. This is a spectroscopic binary star system consisting of a pair of stars orbiting around each other with a separation that can not currently be resolved with a conventional telescope. However, the pair have been resolved using the Mark III Stellar Interferometer at the Mount Wilson Observatory. This allows the orbital elements to be computed, as well as the individual masses of the two stars. The stars complete their highly elliptical orbit every 107 days.

The primary star has a stellar classification of A3 V, which means it is an A-type main-sequence star that is generating energy through the thermonuclear fusion of hydrogen in its core region. The NStars project gives the star a spectral type of kA4 hA5 mA5 Va under the revised MK spectral classification system. The secondary star is a G-type main-sequence star, with a stellar classification of G2V. It is about four magnitudes fainter than the primary; hence the energy output from the system is dominated by the primary star. In a few million years, as the primary evolves toward a red giant, significant amounts of mass transfer to the secondary component is expected.

The primary has been classified as a rapid rotator, with a projected rotational velocity of 73 km/s providing a lower bound on the azimuthal rotational velocity along the equator. It may also be a mildly Am star, which is a class of stars that show a peculiar spectrum with strong absorption lines from various elements and deficiencies in others. In β Arietis, these absorption lines are broadened because of the Doppler effect from the rotation, making analysis of the abundance patterns difficult.

This system has been examined with the Spitzer Space Telescope for the presence of an excess emission of infrared, which would indicate a disk of dust. However, no significant excess was detected.

External links

• GJ 80 Catalog
• Image Beta Arietis
• Beta Arietis by Professor Jim Kaler.
• ARICNS entry
• The Constellations and Named Stars