Gamma Arietis (γ Arietis, abbreviated Gamma Ari, γ Ari) is a binary star (possibly trinary) in the northern constellation of Aries. The two components are designated γ1 Arietis or Gamma Arietis B and γ2 Arietis or Gamma Arietis A (formally named Mesarthim , the traditional name for the Gamma Arietis system). γ1 Arietis may itself be a spectroscopic binary with a low mass companion. The combined apparent visual magnitude of the stars is 3.86, which is readily visible to the naked eye and makes this the fourth-brightest member of Aries. Based upon parallax measurements obtained during the Hipparcos mission, the distance to Gamma Arietis from the Sun is approximately . Properties The double star nature of this system was discovered by Robert Hooke in 1664. The two components have an angular separation of 7.606 arcseconds, which can be resolved with a small telescope. The orbital period of the pair is greater than 5000 years. The brighter component, γ2 Arietis, is an α2 CVn type variable star, a type of star with a strong magnetic field and enhanced spectral lines of some metals, with high chromospheric activity causing brightness changes as the star rotates. Its brightness varies by 0.04 magnitudes with a period of 2.61 days. It is also an Ap star, a type of chemically peculiar star with enhanced lines of many metals. The spectral class has been given as A2IVpSiSrCr, noting the particular strength of lines of silicon, strontium, and chromium, although other lines such as Europium, mercury, and manganese are also stronger than a normal star. This spectral type suggests that the star is an A2-class subgiant. One study identified a low-mass companion to γ2 Arietis, a probable red dwarf in a close orbit. The marginally fainter of the two visible stars, γ1 Arietis, is a Lambda Boötis (chemically peculiar) star with a stellar classification of A0Vnp and a magnitude of 4.64. Lambda Boötis stars are identified based on unusually low abundances of iron peak elements in their spectra. The spectral class has also been given as A0IV-V(n)kB8, indicating that calcium K lines in its spectrum are more typical of a B8 star. Older studies often classified it as B9 or B9.5 with a luminosity class of IV or V, indicating either a main sequence or subgiant. Both of the visible stars have mass of about , luminosities of about , effective temperatures of about , and radii