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Terms to link to: Bayer System Flamsteed System Asterism

Alpha A. Hamal Beta A. Sheratan Gamma A. Mesarthim Delta A. Botein 39 Ari Lilii Borea 41 Ari Bharani

Aries has three prominent stars forming an asterism, Alpha, Beta, and Gamma Arietis. Alpha (Hamal) and Beta (Sheratan) are commonly used for navigation.[27] There is also one other star above the fourth magnitude, 41 Arietis (Bharani[28]).

α Arietis, Hamal, is the brightest star in Aries. Its traditional name is derived from the Arabic word for "lamb" or "head of the ram" (ras al-hamal), which references Aries's mythological background.[18] With a spectral class of K2[13] and a luminosity class of III, it is an orange giant with an apparent visual magnitude of 2.00, which lies 66 light-years from Earth.[12][29] Hamal has a luminosity of 96 L☉ and its absolute magnitude is −0.1.[30]

β Arietis, Sheratan, is the second brightest star in Aries. a blue-white star with an apparent visual magnitude of 2.64. Its traditional name is derived from "sharatayn", the Arabic word for "the two signs", referring to both Beta and Gamma Arietis in their position as heralds of the vernal equinox. The two stars were known to the Bedouin as "qarna al-hamal", "horns of the ram".[31] It is 59 light-years from Earth.[32] It has a luminosity of 11 L☉ and its absolute magnitude is 2.1.[30] It is a spectroscopic binary star, one in which the companion star is only known through analysis of the spectra.[33] The spectral class of the primary is A5.[13] Hermann Carl Vogel determined that Sheratan was a spectroscopic binary in 1903; its orbit was determined by Hans Ludendorff in 1907. It has since been studied for its eccentric orbit.[33]

γ Arietis, Mesarthim, is the fourth brightest star in Aries. It is a binary star with two white-hued components, located in a rich field of magnitude 8–12 stars. Its traditional name has conflicting derivations. It may be derived from a corruption of "al-sharatan", the Arabic word meaning "pair" or a word for "fat ram".[14][18][34] However, it may also come from the Sanskrit for "first star of Aries" or the Hebrew for "ministerial servants", both of which are unusual languages of origin for star names.[18] Along with Beta Arietis, it was known to the Bedouin as "qarna al-hamal".[31] The primary is of magnitude 4.59 and the secondary is of magnitude 4.68.[30] The system is 164 light-years from Earth.[35] The two components are separated by 7.8 arcseconds,[3] and the system as a whole has an apparent magnitude of 3.9.[13] The primary has a luminosity of 60 L☉ and the secondary has a luminosity of 56 L☉; the primary is an A-type star with an absolute magnitude of 0.2 and the secondary is a B9-type star with an absolute magnitude of 0.4.[30] The angle between the two components is 1°.[3], one of the earliest such telescopic discoveries. The primary, γ1 Arietis, is an Alpha² Canum Venaticorum variable star that has a range of 0.02 magnitudes and a period of 2.607 days. It is unusual because of its strong silicon emission lines.[33]

The constellation is home to several double stars, including Epsilon, Lambda, and Pi Arietis. ε Arietis is a binary star with two white components. The primary is of magnitude 5.2 and the secondary is of magnitude 5.5. The system is 290 light-years from Earth.[12] Its overall magnitude is 4.63, and the primary has an absolute magnitude of 1.4. Its spectral class is A2. The two components are separated by 1.5 arcseconds.[30] λ Arietis is a wide double star with a white-hued primary and a yellow-hued secondary. The primary is of magnitude 4.8 and the secondary is of magnitude 7.3.[12] The primary is 129 light-years from Earth.[36] It has an absolute magnitude of 1.7 and a spectral class of F0.[30] The two components are separated by 36 arcseconds at an angle of 50°; the two stars are located 0.5° east of 7 Arietis.[3] π Arietis is a close binary star with a blue-white primary and a white secondary. The primary is of magnitude 5.3 and the secondary is of magnitude 8.5.[12] The primary is 776 light-years from Earth.[37] The primary itself is a wide double star with a separation of 25.2 arcseconds; the tertiary has a magnitude of 10.8. The primary and secondary are separated by 3.2 arcseconds.[30]

Most of the other stars in Aries visible to the naked eye have magnitudes between 3 and 5. δ Ari, called Boteïn, is a star of magnitude 4.35, 170 light-years away. It has an absolute magnitude of −0.1 and a spectral class of K2.[30][38] ζ Arietis is a star of magnitude 4.89, 263 light-years away. Its spectral class is A0 and its absolute magnitude is 0.0.[30][39] 14 Arietis is a star of magnitude 4.98, 288 light-years away. Its spectral class is F2 and its absolute magnitude is 0.6.[30][40] 39 Arietis (Lilii Borea[28]) is a similar star of magnitude 4.51, 172 light-years away. Its spectral class is K1 and its absolute magnitude is 0.0.[30][41] 35 Arietis is a dim star of magnitude 4.55, 343 light-years away. Its spectral class is B3 and its absolute magnitude is −1.7.[30][42] 41 Arietis, known both as c Arietis and Nair al Butain, is a brighter star of magnitude 3.63, 165 light-years away. Its spectral class is B8 and it has a luminosity of 105 L☉. Its absolute magnitude is −0.2.[30][43] 53 Arietis is a runaway star of magnitude 6.09, 815 light-years away.[33][44] Its spectral class is B2. It was likely ejected from the Orion Nebula approximately five million years ago, possibly due to supernovae.[33] Finally, Teegarden's Star is the closest star to Earth in Aries. It is a brown dwarf of magnitude 15.14 and spectral class M6.5V. With a proper motion of 5.1 arcseconds per year, it is the 24th closest star to Earth overall.[4]

Aries has its share of variable stars, including R and U Arietis, Mira-type variable stars, and T Arietis, a semi-regular variable star. R Arietis is a Mira variable star that ranges in magnitude from a minimum of 13.7 to a maximum of 7.4 with a period of 186.8 days.[30] It is 4,080 light-years away.[45] U Arietis is another Mira variable star that ranges in magnitude from a minimum of 15.2 to a maximum of 7.2 with a period of 371.1 days.[30] T Arietis is a semiregular variable star that ranges in magnitude from a minimum of 11.3 to a maximum of 7.5 with a period of 317 days.[30] It is 1,630 light-years away.[46] One particularly interesting variable in Aries is SX Arietis, a rotating variable star considered to be the prototype of its class, helium variable stars. SX Arietis stars have very prominent emission lines of Helium I and Silicon III. They are normally main-sequence B0p—B9p stars, and their variations are not usually visible to the naked eye. Therefore, they are observed photometrically, usually having periods that fit in the course of one night. Similar to Alpha² Canum Venaticorum variables, SX Arietis stars have periodic changes in their light and magnetic field, which correspond to the periodic rotation; they differ from the Alpha² Canum Venaticorum variables in their higher temperature. There are between 39 and 49 SX Arietis variable stars currently known; ten are noted as being "uncertain" in the General Catalog of Variable Stars.[47]