The Summer Triangle
During the early evenings of September the Summer Triangle lies high in the south. In October it is to the south-west and by November it is in the west. To find it first look for the brightest star in the sky. That is Vega in the constellation of Lyra. Next look to it’s left to find Deneb in Cygnus. Finally look below Deneb to find Altair in the constellation of Aquila. These three stars form the summer triangle.
Aquila – The Eagle
Altair is the brightest star in the constellation of Aquila. In Greek mythology, Aquila was the eagle that carried Zeus’ thunderbolts.
On a clear moonless night look just above and to the right of Altair in Aquila using binoculars. You should be able to spot a mysterious dark “E” silhouetted against the faint background glow of the Milky Way.
This strange shape is a dark nebula; a cold cloud of interstellar gas and dust, so dense that it obscures the light from the stars behind it. These dark nebulae are where new stars will eventually be born.
Barnard’s “E” is named after Edward Barnard (1857 – 1923), a Victorian astronomer who compiled a list of dark markings in the sky.
The Arrow and the Fox
The constellation of Sagitta (the Arrow) can be found just above Aquila. Although small, it was recognised as an arrow by several ancient civilisations including the Persians, Hebrews, Greeks and Romans.
Vulpecula (The Fox) lies just above Sagitta. Unlike many other constellations it has no mythology associated with it. Vulpecula was introduced by the Polish astronomer Johannes Hevelius during the late 17th century.
The Coathanger (Brocchi’s Cluster)
The eye and brain are excellent at seeing meaningful patterns in random collections of stars. Asterisms are obvious groupings of stars that are not one of the traditional constellations
The Coathanger is an unmistakable asterism despite being upside down! Find it about one binocular field to the north west of the western end of Sagitta. Although it’s stars appear to be close together, they are a chance alignment at very different distances from us.
The Dumbbell Nebula
A short distance to the east lies the Dumbbell Nebula. It is the biggest and brightest planetary nebula in the northern sky. Find it about half a binocular field north of the eastern end of Sagitta. It looks like a small faint planet just below the central star of a distinctive “M” shaped asterism.
A planetary nebula consists of an expanding shell of gas ejected from an old red giant star late in it’s life. They are relatively short- lived, lasting only a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. They are called planetary nebulae because William Herschel thought that they resembled planets when viewed through his telescope in the 1780’s. The name has stuck although it is misleading.
Images by Jon Marcus and Petr Novak are licensed under a Creative Commons Attribution 4.0 International License.