Alkaid

Alkaid, also known as Eta Ursae Majoris, is the fourth brightest star in the constellation Ursa Major, which is more commonly known as the Big Dipper. It is a binary star system, with the primary star, Alkaid A, being a blue-white main-sequence star of spectral type B3V. Alkaid A is approximately 100 light-years away from Earth and has an apparent magnitude of 1.86, making it visible to the naked eye.

The secondary star, Alkaid B, is a magnitude 13.3 star that orbits Alkaid A with a period of about 700 years. Alkaid B is a red dwarf star of spectral type M4V. The two stars are separated by about 1,500 astronomical units, which is roughly the distance between the Sun and Uranus in our solar system.

Alkaid is located at the tip of the handle of the Big Dipper, which is one of the most recognizable asterisms in the night sky. It is often used as a navigational star, as its position relative to the North Star (Polaris) can be used to determine direction. Alkaid is also known by several other names, including Benetnasch, Benetnash, and Alcor, although the latter is more commonly associated with the star Gamma Ursae Majoris.

In ancient times, Alkaid was associated with various mythological figures, including the Greek hero Hercules and the Roman god Jupiter. Today, Alkaid continues to be a popular target for amateur astronomers, who can observe its blue-white color and use it as a reference point for navigating the night sky.