Altair

Altair, also called α Aquilae, α Aql, is the brightest star in the constellation of Aquila.

It is the twelfth brightest star in the night sky. It is in the G-cloud—a fog of gas and dust known as an interstellar cloud.^[1][2] Altair is an A-type main sequence star with an apparent visual magnitude of 0.77. It is one of the vertices of the Summer Triangle (the other two vertices are Deneb and Vega).^[3] It is 16.7 light-years (5.13 parsecs) from the Sun and is one of the closest stars visible to the naked eye.^[4]

Altair spins rapidly, with a velocity at its equator of about 286 km/s.^[5][6] This is a significant fraction of the star's estimated breakup speed of 400 km/s.^[7] A study with the Palomar Testbed Interferometer showed that Altair is not spherical, but is flattened at the poles due to its high rate of rotation.^[8] Other interferometric studies with multiple telescopes, operating in the infrared, have confirmed this.^[6]