Looking west
Hercules Globular Cluster
Look just above the western horizon after dark on early autumn nights and you’ll see a small rectangle of stars, squashed in at the bottom. This is an asterism known as The Keystone of Hercules and if you look a third of the way down on its right side you’ll see what looks like an unimpressive, out of focus star. Binoculars will show it more clearly, but will still only resolve it into a round smudge of light. This is M13, a condensed mass of several hundred thousand stars, forming a huge ball or globe of suns known as a globular cluster. It is around 23,000 lightyears away.
Deneb
Deneb (Alpha (a) Cygni), the brightest star in the constellation of Cygnus, the Swan, lies to the upper left of M13, past the bright star Vega (Alpha (a) Lyrae). Marking the head of the asterism known as the Northern Cross, it is one of three bright stars which form another asterism, the Summer Triangle.
Deneb is a true giant among the stars, 200 times bigger than our own Sun. It is very powerful too, about 200,000 times more luminous than the Sun, and even though it is over 2,600 lightyears away it is the 19th brightest star in the night sky.
If you look at Deneb through binoculars you will see it is surrounded by countless thousands of fainter stars, thick as pollen grains. This is because it is embedded in…
The Milky Way
To end our tour, look to the western horizon and then slowly tilt your head back. If your eyes are properly adapted to the dark you’ll see what looks like a broad band of pale light rising up from the west and arcing over your head. This is the Milky Way.
Many observers compare the Milky Way’s naked-eye appearance to a plane’s vapour trail or smoke rising up from a distant campfire, but if you look at it with your binoculars you’ll see it is the combined glow of countless billions of faint, pinprick stars. Sweep along the Milky Way with your binoculars and you’ll see knots, clumps and trails of stars embedded within it. In some places, such as down the right side of the Northern Cross, the stars are so plentiful they form star clouds that look like they have been sprayed on the sky with an airbrush.
When you look at the Milky Way you’re looking at our own Galaxy from the inside. It’s a huge spiral of billions of suns, but because we’re inside it we can’t see its curving spiral arms. What we see instead, looking through its flattened disc, is a band of light – which ancient sky-watchers named the Milky Way because it looked like milk sprayed across the sky.
Our Grand Tour complete, we can look forward to the coming months as the nights get even longer and darker, and a new astronomy season is upon us.