mardi 23 septembre 2008

Equuleus 5

Alpha Equulei (α Equ / α Equulei) is a star in the constellation Equuleus. It also has the traditional name Kitalpha or Kitalphar, which is a contraction of the Arabic title Qit'at al Faras (قطعة الفرس), meaning "Part of the Horse".
Alpha Equulei collectively belongs to spectral class G0III and has apparent magnitude +3.92 and a luminosity approximately 75 times that of the Sun. However, the star deceives. Alpha Equulei is a unique spectroscopic binary star consisting of two components. The two stellar components within the system are so close together that the class is mixed, G + A, two spectra present at the same time. The brighter of the two (by about 50%, 45 times brighter than the Sun) is a class G (G0) giant, the fainter a white class A (A5) dwarf. The giant is in the process of dying and most likely (like the dimmer component of Capella) has a contracting helium core, while the dwarf is a common unevolved hydrogen-fuser. The blend of starlight makes actual temperatures difficult to measure, but should respectively be around 5500 and 8500 kelvins. The Kitalpa is approximately 186 light years from Earth.

Delta Equulei is the second brightest star in the constellation Equuleus. It sometimes called by the Arabic name Pherasauval, a contraction of the title Faras al-Awwal (الفرس الأول), meaning "The First Horse".
Delta Equulei is a binary star system about 60 light years away, with a class G0 star and a class F5 one. Their combined magnitude is 4.47, and their absolute magnitude is 3.142. There is controversy as to the exact masses of the stars. One study puts the larger at 1.22 solar masses and the smaller at 1.17, while another pegs them at 1.66 and 1.593. The luminosity of the larger star is calculated to be 2.23 solar, and the smaller to be 2.17.

Beta Equulei (Beta Equ / β Equulei / β Equ) is an A-type main sequence star in the constellation of Equuleus. It has an overall apparent visual magnitude of approximately 5.159.

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