Altair
Star
Altair - the brightest star in Aquila and the 12th-brightest in the night sky, 16.7 light-years away. A white A-type star nearly twice the Sun's mass, it spins so fast - once every ~9 hours, its equator moving at ~285 km/s - that it bulges visibly at the equator, one of the first stars imaged as a flattened disk. It forms the Summer Triangle with Vega and Deneb.
Open in 3D viewSee Altair in the live, interactive 3D map
Key facts
Mass
3.70 × 10³⁰ kg
1.86 M☉
Radius
1,252,260 km
1.8× wider than the Sun
Surface temperature
7,550 K (7277 °C)
Luminosity
4.06 × 10²⁷ W
Spectral type
A7V (white main-sequence star)
Science
Physical
- Mass
- 3.70 × 10³⁰ kg · 1.86 M☉
- Radius
- 1,252,260 km · 1.8× wider than the Sun
- Density
- 450 kg/m³ · 0.45× water
- Spectral type
- A7V (white main-sequence star)
Rotation
- Note
- Rotates once every ~8.9 hours — one of the fastest-spinning bright stars known.
Composition
- By mass
- A white main-sequence star about 1.9 times the Sun's mass and ~11 times its light. It rotates once every ~9 hours — near break-up speed — so its equator bulges outward and is cooler than its poles (gravity darkening).
Temperature
- Surface
- 7,550 K (7277 °C)
Radiation & temperature
- Luminosity
- 4.06 × 10²⁷ W · 10.6 L☉
- Surface temperature
- 7,550 K (7277 °C)
- Peak wavelength
- 384 nm · violet-blue light
Discovery & history
- Method
- Naked-eye star
- Name
- Its IAU proper name Altair comes from the Arabic an-nasr at-ta'ir, 'the flying eagle'. It is Alpha Aquilae, the brightest star of Aquila, the Eagle.
Known since antiquity as a marker of the Eagle, Altair's rapid rotation was inferred from its broadened spectral lines and confirmed in 2007, when interferometers (CHARA, Navy Prototype) resolved its oblate, gravity-darkened disk directly - a rare picture of a star's actual shape.
Images
Images from open archives · credit shown per image