Mizar
What is Mizar?
Stars· Distance 83 ly · quadruple + Alcor. Second star of the Big Dipper's handle. With faint Alcor beside it — the 'horse and rider' — it served as an ancient eyesight test. A telescope splits it again, and each half is itself a binary: six stars in all, counting Alcor.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Mizar is in your sky right now: https://nowsky.org/solar/sky?sel=mizar — location and time set automatically, no login.
Distance and spectral type
Mizar is about 86 light-years away, a white main-sequence star (spectral type A2V), in the constellation Ursa Major. Its apparent magnitude is 2.2, visible to the naked eye.
Stellar figures
| Distance | 83 ly |
|---|---|
| Magnitude | 2.2 |
| Companion | Alcor (4.0) — the naked-eye eyesight test |
| Constellation | Ursa Major |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Behind the name
Arabic "girdle". With faint Alcor it was an ancient eyesight test, and it was the first telescopic double star (1617).
Frequently asked
- How far is Mizar from Earth?
- 83 ly.
- How bright is Mizar (apparent magnitude)?
- 2.2.
- Which constellation is Mizar in?
- Ursa Major.
- Where is Mizar in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
The truth about the Alcor eye test
Alcor beside Mizar is said to have served since antiquity as an eye test — if you can split them, your sight is good. But the pair are 12 arcminutes apart, more than a third of the Moon's width, an easy split for anyone with normal vision. One interpretation holds that the old Arab test used a far harder star than Alcor; another, that in an age without city lights the test was one of faintness — whether a 4th-magnitude star could be seen at all.
The two are physically bound. At 83 light-years Alcor lies about one light-year from Mizar, and in 2009 Alcor itself was found to have a red-dwarf partner, making six stars in all with Mizar's four. The whole system belongs to the Ursa Major moving group — the stars, most of the Big Dipper among them, born together and travelling the same way through space.
The star in depth
Mizar is the second-magnitude star second from the end of the Big Dipper's handle. It lies 83 light-years away and belongs to the Ursa Major Moving Group, the loose cluster that most of the Dipper's stars actually share. Even to the naked eye a fourth-magnitude companion, Alcor, sits right beside it — the pair long known as the 'horse and rider'.
It was split by telescope around 1617, one of the first doubles ever resolved, and in 1889 spectroscopy revealed that Mizar A is itself two stars, making it the first spectroscopic binary. Mizar B is a binary too, and Alcor has a companion of its own, so this small patch of sky holds six gravitationally bound stars. The idea that sharp eyes can separate Alcor survives in Arabic and European folklore alike.
From the northern hemisphere the Big Dipper is up in every season, so finding Mizar is easy. Select it in the Sky view to highlight the Dipper's outline, then zoom in to see Alcor hugging it. In the real sky ordinary binoculars separate the two cleanly.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.