The Milky Way cuts right through the Summer Triangle as seen from a dark sky. Look high in the southeast around 9:30-10 p.m. to spot the Triangle’s three brightest stars — Vega, Deneb and Altair. Just below Vega and Deneb, you’ll see the sausage-shaped Cygnus Star Cloud. Photo: Bob King / News Tribune
With a clear sky in view for tonight, it’s time to return once more to the Milky Way. There are just so many things there to see. Tonight we’ll look at the stretch framed by the Summer Triangle and focus on one of the brightest sections, the Cygnus Star Cloud.
The Cloud is located in Cygnus the Swan (Northern Cross) and measures one outstretched fist across. It’s fabulously rich in stars. I’ll bet this was one of the first places Galileo pointed his telescope back in 1610 when he revealed the true nature of the Milky Way: "For the galaxy is nothing else than a congeries of innumerable stars distributed in clusters. To whatever region of it you direct your spyglass, an immense numbers of stars immediately offer themselves to view, of which many appear rather large and very conspicuous but the magnitude of the small ones is truly unfathomable." So wrote Galileo in his book The Starry Messenger.
I looked at the Cloud in binoculars last night and stars jumped out all over the place. It’s a wonderful place to get that tingly Galilean feeling of discovery. Just below and to the right of the center of the cross figure is a curvy little chain of stars I like to call the Caterpillar. Can you see it? The Cygnus Star Cloud consists of many, many stars stacked up behind one another into the deep distance as we look down one of our galaxy’s spiral arms.
An enormous dark rift defines the cloud’s eastern border. The top part of the rift just below Deneb is often referred to as the Northern Coalsack after its better known counterpart,the Coalsack, near the Southern Cross. The Rift splits the Milky Way down the middle and runs all the way from Cygnus through Sagittarius and down to the southern constellation Carina. It consists of enormous clouds of interstellar dust and gas in the plane of the galaxy that blot out the more distant stars. If you could suck it all up with a monster vacuum cleaner and expose the billions of stars otherwise hidden, the Milky Way would be bright enough to cast shadows.
Start with the Northern Coalsack and follow the Rift across the sky down toward the southern horizon. As you do, your gaze literally reaches across the galaxy, moving from the local spiral arm into a more distant one. The Rift broadens as you go because it approaches our solar system more closely en route from Cygnus to Sagittarius.
The spiral galaxy NGC 891 in the constellation Andromeda is 30 million light years away and home to billions of stars. The dust lane in this galaxy would cut a dark path along the NGC 891 "Milky Way" for an inhabitant living there just as the Great Rift does in our own galaxy. Photo: Jim Misti
Many spiral galaxies like the Milky Way have dark clouds along their equators. Dust left over from the evolution of stars into white dwarfs and supernovas settles there and is used again to create new generations of stars.
When I look up at the Milky Way on a dark August night far from town, I’ll recall the picture of another galaxy, NGC 891. Photos and looking at galaxies through the telescope help me to see and appreciate the full breadth and grandeur of our own galaxy. Those nights leave my neck stiff but with a head full of happiness. Are you ready for some of the same? Grab your binoculars and go out tonight.