As the nights begin to get longer, Stuart Atkinson takes us on a tour of the new season’s astronomical highlights

Stargazers always feel a sense of relief and almost liberation when autumn returns. During summer the night sky doesn’t really get dark enough to see all but the brightest stars and deep-sky objects, so after covering up our telescopes we spend the summer months in a kind of enforced astronomical hibernation, watching the lantern-bright International Space Station arc silently across the sky and picking out a bright planet or two on endless twilight nights while crossing our fingers for the northern sky to be painted with a display of noctilucent clouds. But as summer recedes there actually is an ‘after dark’ again, and a lovely selection of stars, globular clusters, galaxies and other beautiful celestial sights slowly comes back into view. Here we’re going to look at some of the best sights to see in the night sky this autumn and how to find them.

Much the same as the Voyager probes famously went on a Grand Tour of the outer Solar System in the 1970s and ’80s, moving from planet to planet, with this feature newcomers to sky-watching and experienced amateur astronomers alike will be able to embark on their own – rather quicker – Grand Tour of the wonders of the night sky in celebration of this season. So let us star-hop from constellation to constellation and visit one fascinating deep-sky object after another.

Preparation is key

Before you head outside there are a few things you need to do. First and perhaps most importantly of all, you need to find a good observing site. Yes, you’ll be able to see some stars from your garden, but unless you live on a remote Scottish island, or in the middle of ghost-haunted moorland, your view of the sky will be both blocked by neighbouring properties and affected, perhaps even ruined, by light pollution from surrounding streetlights, external security floodlights on buildings and the illuminated signs of shops and pubs. You’ll want to find a spot nearby with as little light pollution as possible, and with as big a view of the sky as possible, and then you’ll be set to enjoy your own Grand Tour. Just be sure to stay safe, to stargaze with others where possible and to take heed of any COVID-related restrictions that happen to be in place.

Of course, you might already have a good observing place: a farm gateway or layby that’s just up the road from where you live, a car park on the outskirts of town, or maybe a nearby beauty spot – but if you don’t then you’ll need to do some research. Google Maps or Google Earth are useful for helping stargazers to find good observing sites. If you can, go and check out your site during the daytime, then you won’t be caught out by any tall trees, buildings or hills that aren’t obvious on the online maps and would spoil your view on a clear night.

“You won’t need a telescope to see the objects featured in this tour, they are all visible to the naked eye”

Also, it’s very important to dress warmly. Autumn nights can feel very chilly and damp, especially after you’ve got used to the long, shorts-and-sandals nights of summer, so retrieve the gloves, hat, scarf and warm jacket you threw into the back of the wardrobe at the end of spring and snuggle back into them again before going out.

As for equipment, you won’t need a telescope to see the objects featured in this tour, they are all visible to the naked eye. However, if you have a pair of binoculars then take those along; they’ll give you better views of the objects once you’ve found them, and ensure you get the most enjoyment from your trip out to a dark sky.

Finally, plan your tour timetable. You’ll want to be at your observing site by around 8:30pm, just as it’s getting properly dark, so take into account the time it will take you to get there when you make your plans, especially if you’re meeting up with other people.

And so, preparations complete, let’s begin the Grand Tour…

Looking east

The Pleiades

We start our tour by looking low in the sky, just above the northeastern horizon. There you will see – as long as there are no trees, hills or buildings in the way –a knot of blue-white stars, roughly the size of your thumbnail held at arm’s length. This is one of the most famous star clusters in the sky: the Pleiades.

This beautiful spill of stars – which is only 444 lightyears from Earth, making it one of the closest star clusters to us – is famously known as The Seven Sisters because, although it contains many hundreds of stars, its seven brightest members can be seen with the naked eye, looking like a miniature version of the Plough. If you have binoculars you will be able to see many dozens of fainter stars dotted around the brightest ones. Whenever stargazers see the Pleiades for the first time in autumn, they know that winter isn’t far away. Then the Pleiades will shine high in the sky all through the night, above and to the right of Orion.

The Double Cluster

Look to the upper left of the Pleiades, halfway between the ‘W’ of constellation Cassiopeia, the Queen and the upside down ‘Y’ of Perseus, the Hero and you’ll see a vague, smudgy… something out of the corner of your eye. This is actually two star clusters (NGC 884 and NGC 869) sparkling together side by side, known, appropriately, as the Double Cluster.

Through your binoculars the Double Cluster will be resolved into two distinct star clusters, looking like piles of salt or sugar grains, so close they are almost touching. The clusters are a gravitationally bound pair. Around 8,100 lightyears away, they are separated by a few hundred lightyears.

The Andromeda Galaxy

Look to the right of the Double Cluster, approximately halfway between it and the Great Square of Pegasus and you’ll see a large, misty smudge with a roughly oval shape. This is M31, the Andromeda Galaxy, a huge spiral galaxy.

M31 is the closest spiral galaxy to our Milky Way, but it’s still so far away that its light takes around 2.5 million years to reach us. This makes M31 famous in astronomy as a distant object that is visible to the naked eye. Through your binoculars M31 is revealed to be a lensshaped haze of light, noticeably brighter in the centre, that covers an area of night sky that’s roughly six times as large as the full Moon.

Looking north

The Plough

Look just above the northern horizon and you’ll see a pattern of stars that will remind you of a large saucepan. This is the famous Plough, or Big Dipper, one of the most easily recognised patterns of stars in the sky – but you might be surprised to learn that it’s not a constellation. The Plough is an asterism, a pattern of stars obvious to the eye that forms part of an actual, larger constellation. The stars of the Plough are part of the constellation Ursa Major, the Great Bear, and represent its hindquarters and tail. Autumn is a very good time of year to see the Plough because it lies parallel to the horizon as darkness falls, and it is in the orientation most people expect it to be.

Mizar and Alcor

If you have reasonably good eyesight and look closely at the star Mizar, (Zeta (z) Ursae Majoris) positioned halfway along the curved handle of the Plough, you’ll see it’s not one star but two, shining very close together. Mizar’s fainter companion is called Alcor (80 Ursae Majoris), and together these two stars are one of the most famous double stars in the whole of the night sky. They were used as a test of eyesight in years gone by. If you can’t split them with your naked eye then don’t worry, as your binoculars will show it.

Polaris

Ask any of your non-astronomer friends to name a star and most will quickly answer the ‘Pole Star’ or ‘North Star’ and a few might even know its official name, Polaris. This is because many people have grown up believing it is the brightest star in the heavens, but this isn’t true. Polaris (Alpha (a) Ursae Minoris) might be the brightest star in Ursa Minor, the Little Bear, but it is only the 48th brightest star in the sky, about as bright as the stars that make up the nearby Plough, so it doesn’t really stand out in the night sky at all. It’s only important because it happens to lie almost directly above the polar axis of Earth, which means all the other stars, their constellations and everything else in the sky appear to rotate around it as Earth spins. Finding it is easy: just go back to the Plough and draw an imaginary line upwards from the two stars known as ‘The Pointers’ – that line will take you to Polaris.

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.

---

IMAGES: MARK FERGUSON/ALAMY STOCK PHOTO