Sky ArchiveTonight

Deneb, tail of Cygnus the Swan

Tonight, look for Deneb, the brightest star in the constellation Cygnus the Swan. The night sky chart at the top of this post presents the view toward the northeast in mid-to-late evening during the month of May. It’s the view from mid-northern latitudes.

This star is part of not one but two striking star patterns. And it’s one of the most distant stars we can see with the eye alone, well over 1,000 light-years away.

Three bright stars with lines connecting them.
Here is the Summer Triangle asterism – three bright stars in three different constellations – as photographed by EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan!

Deneb is part of the Summer Triangle pattern. Deneb – along with the stars Vega and Altair – is part of the famous Summer Triangle asterism, which will be well up in the east in mid-evening next month. On these Northern Hemisphere late spring evenings, you might not be able to see the whole Summer Triangle until later at night. The star Altair will be the last of these three stars to rise. But you can see the bright star Deneb to the lower left of Vega, the Summer Triangle’s brightest star.

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Deneb is also part of a smaller, cross-like pattern. Deneb is the brightest star in the constellation Cygnus the Swan. If you look at the cross-like pattern indicated on the chart at the top of this post, you might be able to imagine Deneb as the point marking the short tail of a long-necked swan flying toward the south. This is how early Arabian stargazers saw it. The name Deneb comes from the Arabic language and means tail, and in skylore Deneb is often said to be the Tail of the Swan. The little star Albireo marks the Swan’s Head.

But there’s another way to see this pattern of stars that works equally well. In more modern skylore, this pattern is sometimes called the Northern Cross. It looks like a cross, right? If you prefer to see the Cross instead of the Swan, Deneb marks the head of the Cross.

Cross or Swan … this is a lovely pattern to pick out on the sky’s dome.

Astronomers know that Deneb is one of the most distant stars we can see with the eye alone. The exact distance to Deneb can only be estimated, with estimates ranging from about 1,425 light-years to perhaps as much as 7,000 light-years. At any of these estimated distances, Deneb is one of the farthest stars the unaided human eye can see. It is so far, that the light that reaches the Earth today started on its journey well more than 1,000 years ago.

More about Deneb: Very distant and very luminous

Bottom line: The star Deneb is part of the Summer Triangle asterism. And it’s part of the constellation Cygnus the Swan, which can also be seen as a Cross. Look for the star Deneb tonight! At well over 1,000 light-years away, it’s one of the most distant stars we can see with the eye alone.

A planisphere is a virtually indispensable tool for beginning stargazers. Order your EarthSky planisphere from our store.

May 20, 2020
Sky Archive

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