About Alnair
Description
Alnair is a blue-white star of spectral type B7IV at magnitude 1.74, the brightest star in Grus (the Crane). Located about 101 light-years from Earth, it has a luminosity of roughly 380 times solar and a surface temperature of about 13,500 K. It is a rapidly rotating star, spinning at about 215 km/s at its equator.
Observing Tips
Alnair is the brightest star in the southern constellation Grus, visible from the southern hemisphere and from northern latitudes south of about 33°N. It lies in a relatively sparse area of sky south of Fomalhaut. Alnair and Al Dhanab (Gamma Gru) form the crane's body. Best observed September through November.
History
The name Alnair comes from the Arabic 'al-nayyir,' meaning 'the bright one.' Grus was defined as a constellation by Petrus Plancius in the late 16th century from Dutch navigators' observations. Before that, its stars were considered part of Piscis Austrinus.
Fun Facts
Alnair's rapid rotation means it completes one full spin in less than a day, compared to the Sun's 25-day rotation period. This rapid spin likely causes the star to be significantly oblate, similar to Vega and Altair.
Observe
1Physical Properties
2Position & Identifiers
3How easy to spot?
| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Easy | Easy | Easy |
| 50 mm finder 50mm finder | Easy | Easy | Easy |
| 150 mm telescope 150mm scope | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Survey Image
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Explore
7
Size Comparison
8
Compare Stars
9
Spectral Classification
10
Hertzsprung-Russell Diagram
11
Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
Discover
15Stellar Notes
16
Light Travel Time Machine
17
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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