Epsilon Boötis - Izar - Purcherrima (double star), 


            Marcos González Troyas

Epsilon Boötis - Izar - Purcherrima (double star)


Acquisition details

June 16, 2014
500×1(8′ 20″)
8′ 20″
Avg. Moon age:
18.56 days
Avg. Moon phase:

Basic astrometry details

Astrometry.net job: 300935

Resolution: 160x188

File size: 4.1 KB

Locations: Observatorio Berruguete, Madrid, Madrid, Spain


Epsilon Boötis (ε Boo, ε Boötis) is a double star in the northern constellation of Boötes. It has the traditional names Izar and Pulcherrima. The star system can be viewed with the unaided eye at night, but resolving the pair with a small telescope is challenging; an aperture of 76 mm (3.0 in) or greater is required.

The brighter member has a stellar classification of K0 II-III, which means it is a fairly late-stage star well into its stellar evolution, having already exhausted its supply of hydrogen fuel at the core. With more than four times the mass of the Sun, it has expanded to about 33 times the Sun's radius and is emitting 501 times the luminosity of the Sun. This energy is being radiated from its outer envelope at an effective temperature of 4,550 K, giving it the orange hue of a K-type star.

The companion star has a classification of A2 V, so it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. This star is rotating rapidly, with a projected rotational velocity of 123 km s–1 By the time the smaller main sequence star reaches the current point of the primary in its evolution, the larger star will have lost much of its mass in a planetary nebula and will have evolved into a white dwarf. The pair will have essentially changed roles: the brighter star becoming the dim dwarf, while the lesser companion will shine as a giant star.



Epsilon Boötis - Izar - Purcherrima (double star), 


            Marcos González Troyas