Vega, Deneb, and Altair

June 28, 2019

The stars Vega, Deneb, and Altair form what’s called the summer triangle, which sweeps overhead all night during the warmer months of the northern hemisphere.

Of the three, you’ve probably at least heard of Vega… one of the brightest stars in the night sky. It’s about 2.5 times the size of the sun, twice as massive, and about 40 times brighter. That may sound like it has quite a leg up on the sun, but if you take into account the enormous range in characteristics of stars out there, they’re fairly similar.

Altair is even MORE like the sun. Just under twice the size and mass, and 10 times brighter. Closer than Vega too at less than 17 light years away.

But the REAL star of the summer triangle, if you’ll pardon my unintended pun… is Deneb.
Deneb is an incredible star. It’s a blue-white supergiant. If you were to replace the sun with Deneb, its surface would extend to about Earth’s orbit—we’d be toast. It’s one of the largest known white stars. And, get this, it’s almost 200,000 times brighter. But enormous, energetic stars like this don’t live long. Deneb is only about 10 million years old.

Despite all of that, Deneb is the dimmest of the three stars in the summer triangle. Why? You can probably figure it out. It’s SO far away. About 2600 light years.

The Summer Triangle will be in the eastern sky after sundown. Vega and Deneb form the short side of the triangle with Altair at the point, closest to the horizon.