mercredi 3 septembre 2008

Bootes 3

Alpha Bootis

Distance (Light Years)
36.7 ± 0.3
Visual Magnitude
Color (B-V)
Names For This Star"Arcturus" is a Greek word meaning "Bear Guard." This name for the star is undoubtedly connected with it's position just to the east of the Ursa Major, The Greater Bear.
Another name for the star is Haris-el-sema, from the Arabic Al Haris al Sama, "The Keeper of Heaven.
Description of the StarThe Hipparcos Catalogue mission discovered Arcturus to be a binary star system. Arcturus A is an orange colored giant K1.5IIIFe-0.5 star. The spectral type implies an effective temperature of the star is about 4300 K and a mass about 20 times that of the sun.
The Visual Magnitude and distance indicate a luminosity 110 times that of the sun. The star has about 28 times the diameter of the sun.
The companion Arcturus B is about 3.3 magnitudes dimmer than A. At 0.255 arc sec of separation, the projected distance between the stars is 2.9 AU.
According to Burnham, Arcturus is the fourth brightest star in the sky.

Izar A
Epsilon Bootis (A component)

Distance (Light Years)
210 ± 11
Visual Magnitude (combined)
Color (B-V)
Names For This StarThe name Izar is Arabic and means "Girdle" or "Belt."
Other names for this star are Mirac, Mirak, Mirach, or Mizar, which derive from Arabic words similar in meaning to "Izar." These alternative names invite confusion, since there other stars which are generally recognized by similar names. See Mirach, Merak, and Mizar.
Description of the StarIzar A is a cool, orange K0-II-III subgiant or giant. about 400 times as luminous as the sun.
Izar is a double star system. The B component is 2.19 magnitudes dimmer than A and separated from it by 2.867 sec of arc, corresponding to a projected distance of 184 AU (4.7 times the radius of the solar system out to Pluto.)

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