Alcor

Definition

Alcor is a star in the constellation Ursa Major, often associated with Mizar as part of a visual double star system. It is located approximately 81 light-years from Earth and is visible to the naked eye.

5 Must Know Facts For Your Next Test

1. Alcor and Mizar form a visual double star, meaning they appear close together in the sky but are not necessarily gravitationally bound.
2. Alcor has an apparent magnitude of about 4.0, making it moderately bright and visible without telescopes.
3. The Alcor-Mizar pair has been historically used as a test of eyesight.
4. Alcor is classified as an A5V type star, indicating it is a main-sequence star with a surface temperature around 8,000 Kelvin.
5. Recent studies suggest that Alcor may have its own companion star, making it part of a more complex multiple-star system.

Review Questions

• What type of star is Alcor classified as?
• How far is Alcor from Earth?
• What historical use did the Alcor-Mizar pair have?

Related terms

Mizar: A nearby star to Alcor and part of the visual double; it is also in Ursa Major.

Visual Double Star: Two stars that appear close together in the sky but are not necessarily gravitationally bound.

Main-Sequence Star: A star that is in the longest-lasting stage of its life cycle, where it fuses hydrogen into helium in its core.