Star profile

Alcor

80 Ursae Majoris · Ursa Major

3D likeness based on its real data · class A · ~8,500 K

What is Alcor

Alcor is the little companion of Mizar in the handle of the Big Dipper, and ancient peoples used it as a test of eyesight — to separate the two stars was proof of a sharp eye. Its name comes from the Arabic «al-jawn», «the horse» or «the dim one». A white A-class star about 82 light-years away, a young flame orbiting Mizar in a multiple system: an inseparable pair to the unaided eye.

Where it is and when to see it

Alcor lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is March, when it culminates around midnight.

From London it never sets and culminates about 87° up.
From New York it never sets and culminates about 76° up.
From Sydney it culminates about 1° above the horizon.

It can be seen from anywhere north of 35° S.

It ranks no. 20 in brightness among the 124 stars of Ursa Major in our catalogue. To find it, start from Alioth, the brightest: it lies about 5° away (a fist at arm's length covers about 10°).

The light you see today left it about 82 years ago.

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Astronomical data for Alcor

Constellation: Ursa Major
Apparent magnitude: 3.99
Distance: 81.7 light years
Coordinates (J2000): RA 201.306° · Dec 54.988°
Catalogue: HIP 65477 · HD 116842

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Other stars in Ursa Major

Ursa Major has 124 stars in Stelvia's catalogue. Here are a few of them.

See all 124 stars in Ursa Major