The summer Milky Way overhead and through the Summer Triangle stars in July, looking up through trees in Banff National Park at Herbert Lake. (Photo by: Alan Dyer/VW Pics/UIG via Getty Images)
Universal Images Group via Getty Images
There is no better way to round off a summer of stargazing — complete with a rare “planet parade” happening right now— than to see the Milky Way arc across the night sky. It’s not always on show, but now is the perfect time, with a crescent moon out of the sky soon after dark this weekend. All you need to do is get yourself under dark country skies and look up. If you do, you’ll find it seemingly trapped within three bright stars — the so-called “Summer Triangle.”
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Where And When To Look
Very high in the sky at this time of year in the Northern Hemisphere is a vast but simple arrangement of three very bright— but very different — stars. Crucially, it’s where to look for the Milky Way if you are under dark skies.
The “Summer Triangle” — an asterism, not an official constellation — comprises Vega in the constellation Lyra, Deneb in Cygnus and Altair in Aquila.
The northern summer Milky Way through the area of the Summer Triangle, showing the change in colour as the Milky Way heads south toward the dustier regions around the galactic core. (Photo by: VW Pics/Universal Images Group via Getty Images)
Universal Images Group via Getty Images
What You’ll See
Vega is the brightest and highest this weekend. It’s one of the most famous stars in the night sky and just 25 light-years distant from the sun. To the left of Vega, also very high in the sky, is Deneb, the 19th brightest star in the night sky. It’s much farther away at 2,600 light-years. It’s so bright because it’s a supergiant star, 20 times the mass and 110 times the radius of our sun. It’s one of the farthest stars that can be seen with the naked eye.
The lowest of the three stars in the Summer Triangle is Altair, the 12th brightest star in the night sky. Like Vega, it’s bright because it’s close, at just 17 light-years away from the sun. Also like Vega, Altair is about twice the mass and radius of the sun.
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Observing Tips
Once you’ve found those three stars, look between Deneb and Altair. You should make out a dense concentration of stars and, if you’re under dark skies, dark bands within them. You’re looking at the spiral arms of the Milky Way from within one. The collected brightness of billions of stars, the Milky Way streams between Deneb and Altair, and then down to the horizon in the south. Closer to the horizon, you may see the constellation Sagittarius, inimitable because of its easily recognisable shape — a Teapot. Those dark bands are vast dust lanes in the galaxy, blocking your view of stars behind.
Can’t see the Milky Way and its dark bands? Stay outside longer to let your eyes adjust to the darkness — or get yourself under a dark sky.
What’s Next In The Night Sky
Have you seen the “planet parade” happening in the east an hour before sunrise? Jupiter and Venus dominate it, in terms of brightness, but Saturn in the south is also easy to see. Those three naked-eye planets are joined by Neptune (close to Saturn) and Uranus, though both of those outer planets are impossible to see with the naked eye.
For exact timings, use a sunrise and sunset calculator for where you are, Stellarium Web for a sky chart and Night Sky Tonight: Visible Planets at Your Location for positions and rise/set times for planets.
Wishing you clear skies and wide eyes.