Alnitak
What is Alnitak?
Stars· Distance ~1,260 ly · triple system. The eastern star of Orion's Belt; the name means 'the girdle' in Arabic. It is the hottest O-type supergiant visible to the naked eye, and the Horsehead and Flame nebulae hang just south of it — a region beloved by astrophotographers.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Alnitak is in your sky right now: https://nowsky.org/solar/sky?sel=alnitak — location and time set automatically, no login.
Distance and spectral type
Alnitak is , in the constellation Orion. Its apparent magnitude is 1.8, visible to the naked eye.
Stellar figures
| Distance | ~1,260 ly |
|---|---|
| Magnitude | 1.8 |
| Type | O9.5 supergiant — among the hottest naked-eye stars |
| Constellation | Orion (east end of the Belt) |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Behind the name
Arabic "the girdle". The eastern belt star, with the Flame and Horsehead nebulae hanging just below it.
Frequently asked
- How far is Alnitak from Earth?
- ~1,260 ly.
- How bright is Alnitak (apparent magnitude)?
- 1.8.
- What kind of object is Alnitak?
- O9.5 supergiant — among the hottest naked-eye stars.
- Which constellation is Alnitak in?
- Orion.
- Where is Alnitak in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Alnitak, three stars in one
Alnitak is one star to the eye but three. The primary, Aa, is an O9.5 blue supergiant of 33 solar masses; a B0 star, Ab, circles it at 11 AU every seven years; and 2.4 arcseconds away a 4th-magnitude B star, B, orbits over more than 1,500 years. Ab was first resolved by interferometry in 1998, and B can be seen in a small telescope on a night of steady seeing — the trick is to find the small point pressed against the bright primary.
Of the three belt stars Alnitak is nearest to Earth (about 1,260 light-years), yet its light left in the twelfth century. All three belong to the Orion OB1 association, a group of hundreds of young massive stars born together, and within a few million years they will become supernovae in turn, undoing Orion's belt. The belt we see now is, on a cosmic clock, a brief coincidence.
The star in depth
Alnitak is the eastern (left-hand) star of Orion's Belt. An O-type blue supergiant with a surface near 30,000 K, it ranks among the hottest stars the naked eye can see. It lies about 1,260 light-years away, shines with roughly 250,000 solar luminosities, and is actually a triple system of hot stars.
The sky around it is the most famous nebula field in the heavens. Directly south hangs the dark silhouette of the Horsehead Nebula, and to the east glows the Flame Nebula — both sculpted or lit by Alnitak's fierce ultraviolet radiation. The star sheds mass in a strong wind and, at over 30 solar masses, is destined to explode as a supernova.
On winter evenings Alnitak is the left-most star of the Belt. Select it in the Sky view and switch on the extended-objects layer to see the Horsehead and Flame marked right beside it, so you can point to that photographed patch of sky yourself.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.