visual binary A visual binary is a gravitationally bound binary star system that can be resolved into two stars. These stars are estimated, via Kepler's third law, to have periods ranging from a few years to thousands of years. A visual binary consists of two st ...
star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
system in the northern
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
of
Aries
Aries may refer to:
*Aries (astrology), an astrological sign
*Aries (constellation), a constellation in the zodiac
Arts, entertainment and media
* ''Aries'' (album), by Luis Miguel, 1993
* ''Aries'' (EP), by Alice Chater, 2020
* "Aries" (song), ...
. Its name is a
Bayer designation
A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
that is Latinized from ε Arietis, and abbreviated Epsilon Ari or ε Ari. This system has a combined
apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...
of 4.63 and can be seen with the
naked eye
Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...
, although the two components are too close together to be resolved without a telescope. With an annual
parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
shift of , the distance to this system can be estimated as , give or take a 7 light-year
margin of error
The margin of error is a statistic expressing the amount of random sampling error in the results of a Statistical survey, survey. The larger the margin of error, the less confidence one should have that a poll result would reflect the result of ...
. It is located behind the dark cloud MBM12.
The brighter member of this pair has an apparent magnitude of 5.2. At an
angular separation
Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When t ...
of from the brighter component, along a
position angle
In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the Celestial pole, north celestial pole (NCP), turning pos ...
of , is the magnitude 5.5 companion. Both are
A-type main sequence star
An A-type main-sequence star (A) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1.7 ...
s with a
stellar classification
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction gratin ...
of A2 Vs. (The 's' suffix indicates that the
absorption line
Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption (electromagnetic radiation), absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. Th ...
s in the
spectrum
A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
are distinctly narrow.) In the 2009 ''Catalogue of Ap, HgMn and Am stars'', the two stars have a classification of A3 Ti, indicating they are
Ap star
Ap and Bp stars are chemically peculiar stars (hence the "p") of spectral types A and B which show overabundances of some metals, such as strontium, chromium, or europium. In addition, larger overabundances are often seen in praseodymium and neodym ...
s with an anomalous abundance of titanium. Within the measurement margin of error, their projected rotational velocities are deemed identical at 60 km/s.
Name
This star system, along with δ Ari, ζ Ari, π Ari, and ρ3 Ari, were Al Bīrūnī's ''Al Buṭain'' (ألبطين), the dual of ''Al Baṭn'', the Belly. According to the catalogue of stars in the ''Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars'', ''Al Buṭain'' were the title for five stars : δ Ari as ''Botein'', π Ari as ''Al Buṭain I'', ρ3 Ari as ''Al Buṭain II'', ε Ari as ''Al Buṭain III'' and ζ Ari as ''Al Buṭain IV''
In Chinese astronomy, Epsilon Arietis may be or may be part of ''Tso Kang'' (from Cantonese ''zogang'', Mandarin pronunciation ''zuǒgēng'').Chevalier, S., and Tsuchihashi, P., (1911): "Catalogue d'Étoiles fixes, observés a Pekin sous l' Empereur Kien Long (Qianlong (Chien-Lung)), XVIIIe siecle", ''Annales de l'Observatoire Astronomique de Zô-Sé''. (Yi Shi Tong) (1981): .