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Northern Cross

StarDate: 
January 6, 2019

A star pattern that runs along the spine of the Milky Way is quite prominent at this time of year. It’s the Northern Cross — part of the constellation Cygnus, the swan.

During summer evenings, the swan flies parallel to the horizon, so it really does resemble a graceful bird. Now, though, it stands almost straight up from the western horizon at nightfall. In that configuration, it forms a cross. Its brightest star is Deneb, at the top of the cross.

If you have a dark skywatching site, you’ll see the subtle band of the Milky Way flanking the cross. That’s the combined light of millions of stars in the disk of the Milky Way galaxy. The stars are so far and faint that we don’t see them as individual points of light. But there are so many of them that their light merges to form a soft, milky glow.

The Northern Cross lies along the plane of the galaxy’s disk. The northern half of the disk is to the right of the cross, with the southern half to the left. It’s a bit darker behind the cross. That’s because thick clouds of dust in that region absorb the light of the stars behind them.

That won’t always be the case. Over many millions of years, some of the clouds will collapse and give birth to new stars. Some of the newborns will be supergiants like Deneb — some of the hottest, brightest, and most massive stars in the galaxy. Those stars will create new patterns in the night sky — new figures to replace the Northern Cross.

 

Script by Damond Benningfield

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