Eta

Its story

Eta Aquilae is one of the first Cepheids ever recognised: in 1784 Edward Pigott noticed her brightness changing rhythmically, and that pulse, repeated in hundreds of similar stars, would a century later become the ruler with which we measure the universe. Her light swings from magnitude 3.5 to 4.3 every 7.18 days: a yellow supergiant 3,400 times more luminous than the Sun, beating at 1,380 light-years.