Tonight the Summer Triangle is above the horizon again after its winter absence. The bright trio of Altair, Deneb and Vega lies embedded in the summer Milky Way. Except for the previously mentioned three, there are few bright stars in this region, but there are literally millions of dimmer ones. Scan with your binoculars from Deneb leftwards towards Sagittarius – innumerable stars will be revealed. Even more may be seen if you wait a couple of days for the too bright Moon to get out of the way. On the chart you will see a number of tiny circles; each one marks the location of a star cluster visible in your binoculars. The brighter objects have names or catalog numbers listed on the chart.
Among the wonders in the sky this evening viewable with binoculars is the Great Cluster in Hercules (M13) which we have mentioned before. It’s the brightest globular cluster in the northern sky, but take a moment to compare it with Omega Centauri (mentioned last month) still visible in the deep southern sky. M13 has 25 to 50 thousand stars in it whereas Omega Centauri has about a million. The Wild Duck Cluster (M11) in the exceedingly dim constellation of Scutum (the shield) has a V shaped pattern of stars superimposed upon it that looks like a flock of flying ducks to some people.
The beautiful constellation of Cygnus (the swan) contains the bright star Deneb, whose name means “tail.” It’s one of the relatively few constellations that looks something like its name. Cygnus contains the asterism the Northern Cross – much larger than it’s southern counterpart. The mythology surrounding Cygnus is somewhat confused; probably the most common story is that Zeus disguised himself as a swan to seduce the human woman Leda and placed a swan’s image in the sky to commemorate his victory. Leda later gave birth to the Gemini Twins and the famous Helen of Troy.
Aquila, the eagle, contains the bright star, Altair, and a number of star clusters, but they are on the dim side. Aquila is notable for having two novas (exploding stars) within its boundaries within historic times. The brighter one, in 389 BC, was as bright as Venus! More recently the second, in 1918 was brighter than Altair. The star Lambda Aquilae has an unusual distinction, it is scheduled to be visited by NASA’s probe Pioneer 11 – in about four million years. The government has no long term plans for the star, the probe just happened to be going in that direction when NASA was through with it.
See you next time!
Mr. Usher is President of the Everglades Astronomical Society which meets every second Tuesday at 7:00PM at the Norris Center, Cambier Park, Naples.