Summer Triangle Corner: Altair – NASA Science

Altair is the last stop of our trip around the summer triangle! The latest asterism star to get up for observers of the northern hemisphere before the start of the summer, Altair Brillant is above high level at sunset at the end of the season in September. Altair could be the most unusual of the three stars in the triangle, because of its high speed: this star turns so fast that it seems “crushed”.

Altair is the brightest star of the Aquila constellation, the eagle. A very brilliant star, Altair holds a notable place in the mythologies of cultures around the world. As discussed in a previous article, Altair represents the vacancies in the old tale “Cowherd and the Weaver Girl”. Although described as part of an eagle by ancient peoples around the Mediterranean, it was also considered to be part of an eagle of the Koori people in Australia. They saw the star itself as representing an eagle with a corner and two stars nearby like its women, a pair of black swans. More recently, one of the first domestic computers was appointed according to The Star: The Altair 8800.

The rapid spinning of Altair was detected for the first time in the 1960s. The narrow observations that followed tested the limits of the technology available for astronomers, which finally led to direct images of the form and surface of the star using a technique called interferometrywhich combines the light of two or more instruments to produce a single image. Predictions on the way in which the surface of a massive star in rapid rotation would appear faithful to observations; The models predicted an crushed form, almost “similar to a pumpkin” instead of a round sphere, as well as a gradation effect along the enlarged equator, and the observations confirmed it!

This equatorial gradation is due to a phenomenon called Gravity. Altair is wider in equator than on the poles due to the centrifugal force, which leads to the mass of the star outside the equator. As a result, the densest poles of the star are warmer and brighter, and the less dense equator being cooler and therefore altering. This does not mean that the equator of Altair or other stars which turn quickly are in fact dark, but rather that the equator is dark compared to the poles; This is similar in a sense with solar stains. If you were to observe a solar spot alone, it would seem blindly brilliant, but it is cooler than the surrounding plasma in the sun and therefore seems dark, however.

While summer ends, you can still make a trip around the summer triangle with this activity of the Night Sky Network. Mark some of the sites in and around the summer triangle to: bit.ly/triangletrip.

Originally published by Dave Prosper: August 2020
Last update by Kat Troche: July 2025