Merak

Merak (Beta UMa, β Ursae Majoris, β UMa) is a star with a stellar classification of A1 V, making it a fairly typical main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The effective temperature of the outer envelope is about 9,225 K, giving it a white-hued glow that is typical for A-type stars.

Observation of the star in the infrared reveal an excess emission that suggests the presence of a circumstellar debris disk of orbiting dust, much like those discovered around Fomalhaut and Vega. The mean temperature of this disk is 120 K, indicating that it is centered at a radius of 47 Astronomical Units from the host star.

Beta Ursae Majoris is one of five stars that form a part of a loose open cluster called the Ursa Major moving group, sharing the same region of space and not just the same patch of sky by our perspective. This group has an estimated age of about (500 ± 100) million years. As the members of this group share a common origin and motion through space, this yields an estimate for the age of Beta Ursae Majoris. Two stars are known to be located in relatively close proximity: 37 Ursae Majoris at 5.2 light-years (1.6 pc) and Gamma Ursae Majoris at 11.0 light-years (3.4 pc).