You might think it’s not possible for a star to be too bright for astronomers. After all, they’re always developing new telescopes and instruments to bring in more light from the stars. But a few stars are too bright for some telescopes.

An example is Deneb, the leading light of Cygnus, the swan. It’s too bright for Gaia, a space telescope. Gaia’s detectors are designed to plot the locations and motions of more than a billion stars. Most of those stars are far and faint. Deneb is brilliant by comparison, so it would overwhelm Gaia’s detectors.

That’s too bad, because astronomers would really like to know Deneb’s distance. It’s one of the biggest, brightest, and heaviest stars in our region of the galaxy. And it’s likely to end its life as a supernova — a blast that’ll rip the star to bits. But without a precise distance, all the other numbers are wobbly.

Estimates put the distance at roughly 1500 to 3,000 light-years. At the larger distance, it would have to be much bigger and brighter to look so bright in our sky.

The best numbers say Deneb is about 20 times the mass of the Sun and 200 times the Sun’s diameter. That puts the star at up to 200 thousand times the Sun’s brightness — enough light to overwhelm a telescope.

Deneb is high in the east-northeast at nightfall. It marks one point of the Summer Triangle. It’s below the triangle’s brightest star, Vega — a remote but brilliant light for summer nights.

Script by Damond Benningfield

Support McDonald Observatory