Alnair
HIP 109268; Alpha Gru
Physical Properties
Position & Identifiers
Visibility
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Multiple Star System
Eyepiece View
Sep: 17.0″ · PA: 155° · N up, E left
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 3.1″
Size Comparison
Stellar Lifecycle
Spectral Classification
Hertzsprung-Russell Diagram
Blackbody Spectrum
Stellar Absorption Spectrum
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Stellar Notes
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About Alnair
Description
Alnair is the brightest star in the constellation Grus (the Crane) at magnitude 1.74, located about 101 light-years from Earth. It is a blue-white subgiant of spectral type B7IV, about 4 times the mass of the Sun and roughly 380 times more luminous. Alnair rotates rapidly, with a projected rotational velocity of about 215 km/s.
Observing Tips
Alnair is a Southern Hemisphere star, visible from latitudes south of about 37°N. It marks the eye or beak of the Crane and helps identify the constellation Grus, which lies south of Fomalhaut. Together with the other bright stars of Grus, it forms a graceful pattern in the autumn/winter sky of the Southern Hemisphere. Best observed from September through November from southern latitudes.
History
The name Alnair comes from the Arabic 'al-Nayyir' meaning 'the bright one,' originally referring to the brighter star in the tail of the Southern Fish. The constellation Grus was introduced by Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman in the late 16th century from observations made during voyages to the East Indies.
Fun Facts
Alnair is a rapid rotator, spinning at over 200 km/s at its equator — about 100 times faster than the Sun. This rapid rotation likely gives it a noticeably oblate shape, though this has not yet been directly measured. It marks the transition point in our list between the 'first magnitude' stars (brighter than 1.5) and the slightly fainter members of the brightest star club.