Take in the celestial targets of our home Galaxy with Stuart Atkinson’s winter observing tour
Seeing the misty, mottled arch of the Milky Way spanning the sky late on a clear summer night is one of the most enjoyable and memorable experiences for astronomers. It’s right up there with your first view of Saturn’s rings through a telescope and seeing a bright fireball skip and flare across the sky during a meteor shower. But why discuss the Milky Way at this time of year? Everyone knows that you can only see the Milky Way during the summer – that it’s a ‘summer sight’, right?
Wrong. The Milky Way is still there on these frosty winter nights, it’s just not as dramatic or obvious. While the summer Milky Way is a naked-eye wonder, a broad trail of starry froth and foam that splits the sky in two, the winter Milky Way is not so obvious and more of a spectacle to seek out. It’s dappled on the sky, and if you take the time and trouble to look at it you’ll be rewarded with some lovely sights. You’ll see another side of the Milky Way; instead of the bright gaseous nebulae of summer, such as the famous Lagoon and Trifid Nebulae, what you will see is a host of sparkling star clusters.
We’re going to go on a tour of the midwinter Milky Way and take in some of these sights. Half are visible to the naked eye, and you’ll need a pair of binoculars or a small telescope to see the rest. One thing’s for sure, all of the sights are worth tracking down after you’ve taken your obligatory nightly look at the Pleiades and the Orion Nebula.
On the next clear, frosty night, before starting the tour pull on several pairs of socks and wrap up in your warmest jacket, hat and gloves. If you look like a seven-year-old child who has been dressed by their mum for a walk on a cold, snowy day, you’ll be fine.
Head out at around 11:30pm and go to the darkest spot you can find. Straight away you’ll see the constellation of Orion, the Hunter standing above the southern horizon, looking splendid with his famous Belt of three icy blue-white stars pulled tightly around his waist and ruddy-hued Betelgeuse (Alpha (α) Orionis) glowing at his shoulder.
All the objects on this tour lie close to Orion, in the southern part of the sky. Before you begin the tour, let your eyes adapt properly to the darkness; this takes about half an hour. Then let us embark!
Sights for setting off
The first targets can all be seen with the naked eye under good conditions, but binoculars will bring out their beauty
1. The Christmas Tree Cluster, NGC 2264
Located a short distance above and left of Betelgeuse (Alpha (α) Orionis), this open star cluster is 2,200 lightyears away and spans about 25 lightyears. At mag. +4.0 it’s easy to see with the naked eye as a small smudge of light. It contains around 80 stars, and gets its nickname from the fact that observers think it resembles a Christmas tree when viewed through a telescope. The Cone Nebula is nearby, but is too faint to see without a large telescope.
2. The Shoe-Buckle Cluster, M35
One of the most popular star clusters in the northern sky, M35 can be found high above Orion, close to the foot of one of the Twins of Gemini, which explains its (little-used) nickname. At mag. +5.0, it’s a visually large object and on a clear night is easy to see with the naked eye as a misty patch above Orion. M35 contains perhaps 500 stars, and the brightest hundred or so are a lovely sight through binoculars and small telescopes, looking like spilled salt grains. The cluster is approximately 35 lightyears across and lies 3,000 lightyears away from us.
3. M47
Often overlooked because of the bigger, brighter star clusters around it, M47 is a treat to observe on a frosty night. This loose cluster of around 50 stars can be found to the upper left of Sirius (Alpha (α) Canis Majoris) and covers an area of sky the same size as the Moon. At mag. +4.4 it is an easy naked-eye object if you take the time to look for it. M47 is 1,600 lightyears away from our Solar System.
NGC 2264 is said to resemble a Christmas tree, beneath which lies the Cone Nebula 
M47 is one of the least densely populated open clusters 
Sirius shines like a beacon and serves as a pointer to nearby sights 
M41 may be overshadowed by Sirius, but its silvery stars make it a beautiful sight in its own right 
Near one of Gemini’s feet, M35 is filled with an abundance of stars
4. The Little Beehive Cluster, M41
If this bright, mag. +4.5 open star cluster were anywhere else in the northern sky it would be much more famous and popular. But because it lies close to and directly beneath bright Sirius, which never rises high in the sky as seen from mid-latitudes, the Little Beehive Cluster is something of a ‘tree-scraper’ for many winter observers. If you have a clear, low southern horizon, on mid-winter nights you should be able to find M41 easily and it really is a lovely sight through binoculars and small telescopes, resembling a smaller version of M44, the Beehive Cluster in Cancer. The cluster is a long way away, more than 2,300 lightyears distant, and its 100 or so silvery stars cover an area of the sky as wide as a full Moon.
5. Sirius, the ‘Dog Star’
Shining down to the lower left of Orion’s famous Belt, magnificent Sirius blazes away at mag. –1.46, making it the brightest star in the night sky by a significant margin. Because it lies so low in the sky, at mid-latitudes Sirius is often seen through lots of turbulent air that boils above the horizon. As a result, its light gets broken up, causing it to sparkle and flash dramatically, much like a finely cut jewel catching the sunlight. Sitting nine lightyears away from Earth, Sirius – also known as the ‘Dog Star’ – is the fifth closest star to our Sun.
Taking a closer look
Break out your binoculars or telescope for the next part of the tour and explore more of the Milky Way’s deep-sky objects
6. The Rosette Nebula
Photographs show the Rosette Nebula as a pretty, rose-like bloom of pink and red gas to the left of Betelgeuse. But despite shining at mag. +5.5, its width and low surface brightness means that with the naked eye, it appears as a vague smudge, even on the darkest of clear nights. The nebula is best viewed through binoculars or a small telescope, but even then it can look like a ghostly patch. For most amateur photographers it’s probably best enjoyed photographically, on long-exposure images, giving you a good reason, perhaps, to start your journey into astrophotography (see the ‘Photographing the Milky Way’ box, on page 33).
7. The Heart-Shaped Cluster, M50
When you look at this 3,200 lightyear-distant, mag. +5.9 open star cluster through your binoculars or telescope you will see a handful of brighter stars surrounded by much fainter ones. But you may be left scratching your head with regard to how the Heart-Shaped Cluster, M50, got its nickname, because it’s never looked anything like a heart to me. Nevertheless, this target is still worth tracking down on a cold winter’s night and you’ll find it glittering serenely above and slightly to the left of Sirius.
8. M46
This rich, mag. +6.0 open star cluster can be found a short distance over to the left of Sirius and it contains between 100 and 500 ‘pollen grain’ stars, surrounded by a cage of brighter suns. If you look at M46 through a telescope at high magnification, you might be able to see that a tiny planetary nebula appears to be embedded within it. In fact, this is all a trick of perception, as NGC 2438 is several thousand lightyears closer to us than M46 and isn’t remotely associated with the cluster.
Although faint and dispersed, there are many blue giant stars to spot in NGC 2301 
It’s easy to see how IC 2177 earned its ‘Seagull Nebula’ nickname 
Does M50 resemble a heart or even a blunt arrowhead? You decide 
Although M46 lies thousands of lightyears away, the open cluster is vast and has an apparent diameter that is almost equal to that of a full Moon 
Long-exposure images are one of the best ways to enjoy the Rosette Nebula
9. Hagrid’s Dragon Cluster, NGC 2301
NGC 2301 has a number of aliases. Besides its New General Catalogue designation, it’s also known as Hagrid’s Dragon Cluster and Copeland’s Golden Worm. But despite boasting these dramatic nicknames, it is likely that few people reading this have even heard of this mag. +6.0 loose, open cluster. This is hardly surprising because NGC 2301’s stars are faint and spread far apart. In fact, through a telescope it looks more like a ragged line of stars than an open cluster. But with the help of a little imagination, you might just be able to see the shape of a dragon. When you do, perhaps you’ll consider a third nickname for the cluster, Norberta, the name of the dragon that belonged to Rubeus Hagrid in the Harry Potter books. You’ll find the cluster roughly halfway between Orion’s Belt and Procyon (Alpha (α) Canis Minoris), the brightest star in Canis Minor.
10. The Seagull Nebula, IC 2177
Just a short distance above and to the left of the brilliant star Sirius lies a very faint nebula surrounding an 8th magnitude star. At mag. +10.0, the Seagull Nebula will present you with a real Christmas challenge, because it can only be seen through a telescope on a beautifully clear, Moon-free night from a site that’s free from light pollution. Even if you do pick it up as a vaguely M-shaped smudge, you’ll probably wonder why IC 2177 is nicknamed after a screeching, chip-stealing seaside bird! But the Seagull’s wings and head do appear quite pronounced in long-exposure photographs.
The geometry of the winter Milky Way
The view of our Galaxy in the night sky reveals how our perspective changes as Earth orbits the Sun
If you’ve ever wondered why the Milky Way looks so different in the winter compared to its appearance in the summer, it is because of our Solar System’s position within the great Catherine wheel of sparkling stars that is our Galaxy. When we look out from Earth on a clear night during the summer months we’re looking in towards the centre of the Milky Way, and also looking through one of its densely packed, nearby spiral arms, so we see a lot of stars – countless billions of them, in fact – looking like mist or smoke. In winter however, those parts of the Milky Way are hidden from us by the Sun and we’re looking outwards to where the stars are much less densely packed, so the Milky Way looks a lot less striking. But it’s still there and if you go to a dark-sky site, you’ll see it easily enough. Furthermore, if you take the time to sweep your eyes, binoculars and telescopes along it, you’ll see lots of fascinating objects embedded within it too.
Photographing the Milky Way
If you’re observing the winter Milky Way, why not see if you can capture an image of it as well?
Almost every issue of BBC Sky at Night Magazine features at least one gorgeous image of the bright summer Milky Way, some taken with just mobile phones. If you want to photograph the winter Milky Way however, you’ll need a digital SLR camera on a tripod or a tracking mount, because it’s much fainter than its summer counterpart, and too faint and diffuse for most phone cameras to pick up. Fit your camera with a wide-angle lens, set it to an ISO of 800 or higher, point it towards Orion, the Hunter and then nudge it to the left so Orion is on the right of the frame.
Using a cable release to reduce vibrations, take the longest exposure you can get away with before the stars trail or your local light pollution fogs the image. You’ll see a misty band to the left of Orion, stretching from beside Sirius up into the constellations of Perseus and Cassiopeia, much fainter than the beautiful summer Milky Way, but still there. If you take multiple images, you can stack them using free software to make the equivalent of one very long exposure, and then process that stacked image to bring out the faint stars of the winter Milky Way.
For more astrophotography tips, visit www.skyatnightmagazine.com/astrophotography
Stuart Atkinson is a lifelong amateur astronomer and author of 11 books on astronomy