By Mike P. Usher
Look eastwards about 11:00 PM and locate the three stars of the Summer Triangle – Vega, Altair and Deneb. These are quite bright stars, and if you can see any stars at all in the sky tonight, you will see these. The Summer Triangle is not a traditional asterism, but was popularized by Sir Patrick Moore a few decades ago.
Vega and Altair are fairly close neighbors of the Sun, which is the primary reason they are so bright, being only 25 and 16 light years away, respectively. Deneb, on the other hand, is really bright (astronomers say it’s very luminous) being some 70,000 times brighter than the Sun. Even at 1,550 light years away it still shines at magnitude 1.25.
Each of the stars of the Summer Triangle belong to their own prominent constellation; probably Cygnus the Swan is the easiest to pick out in a light polluted sky. Cygnus is also known as the Northern Cross and is considerably larger than its southern counterpart. Deneb marks the tail of the swan, and the fainter star, Albireo, marks the beak. Albireo is a beautiful colored double star, with the individual components being blue and gold. To see them, however, you will need high-powered binoculars held rock steady. If you have access to a small telescope you will have an easier time seeing them.
Cygnus lies in the middle of the Milky Way; sweeping the area with binoculars is always a rewarding experience. If observing naked eye from a dark site, you will note that the Milky Way divides in two before reuniting in nearby Aquila. This is actually a cloud of non-luminous gas and dust hiding the millions of stars behind it. The only stars you see here are the ones lying between us and the cloud.
See you next time!
Mr. Usher is president of the Everglades Astronomical Society, which meets the second Tuesday each month at 7 PM in the Norris Center at Cambier Park in Naples.