The dramatic constellations of winter
Katrin Raynor-Evans takes a stargazing journey around the season’s favourite targets
As the Northern Hemisphere makes a transition from autumn to winter and leaves behind the season of mists and mellow fruits, darkness continues to lengthen and the familiar sights that winter skies have to offer are welcomed with open arms, like greeting old friends. The changing of the seasons brings a changing in the constellations – slowly nudged from east to west as we continue our journey around the Sun. ▲ Looking south: the night sky holds many of winter’s most recognisable constellations
If you’re a complete beginner to constellations, you may be wondering what they are. Quite simply they are grouped patterns of stars in our night sky. For thousands of years our ancestors looked to the sky, and observed and named them after animals, objects and mythological characters. You will need a bit of imagination as you try to identify each one as the constellation often looks nothing like its name!
In 1930, the International Astronomical Union formally recognised 88 constellations that can be
identified on the celestial sphere – an imaginary globe that surrounds Earth. Each constellation can be found using celestial coordinates: right ascension, and declination. These are similar to latitude and longitude, but don’t worry, you can easily find the constellations just by recognising the pattern.
Some constellations are visible all year round and never sink below the horizon so you can see them whenever there is a clear sky. These are called circumpolar as they are close to the celestial poles, the imaginary point in the Northern and Southern Hemispheres where the line of Earth’s axis extends out into space to meet the celestial sphere.
Colder, clearer evenings are perfect for enjoying the winter constellations as well as a few deep-sky objects like galaxies, star clusters and nebulae found within them. You can see these beautiful pin-prick patterns of light, hot fiery stars and clouds of dust and gas with your naked eye, using binoculars or a telescope. Best of all, you don’t need to be in a completely dark-sky area to see them.
This short 360˚ tour highlights a handful of constellations that, with a clear horizon, are easy to spot after 20:00 UT and picks out what you may find hiding within them. If your horizon is obstructed by trees or buildings, you may need to wait a little longer until the constellation is higher in the sky. So, wrap up warm, grab this guide and step outside.
Hunting Orion
If you were to ask any astronomer which winter constellation you should choose to kick off your stargazing journey, the answer will be Orion, the Hunter (see picture, above). Dominant against the darkness and easy to recognise, we can use it to navigate, so we’ll begin here.
Orion can be found rising in the east after sunset and it’s easy to identify from the three stars aligned in an almost straight line. These three stars – Alnitak (Zeta (z) Orionis), Alnilam (Epsilon (e) Orionis) and Mintaka (Delta (d) Orionis) – form Orion’s Belt, which is an example of an asterism (a pattern of stars within a constellation). Orion is a winter favourite because of its two blazing, non-Belt stars – Betelgeuse (Alpha (a) Orionis), a bright orange star 1,000 times bigger than our own Sun, and Rigel (Beta (b) Orionis), a cooler blue supergiant – and its fantastic nebula.
The Orion Nebula, M42, lies in the centre of Orion’s Sword, a shorter line of three fainter stars that hangs down from the Belt. The nebula looks like the middle ‘star’ of the Sword to the naked eye, but a bit fuzzier than the stars above and below it. Composed of dust and gas and located 1,344 lightyears away, it is a famous nebula for naked-eye observing and perfect for beginners. A pair of 10x50 binoculars will enhance this diffuse cloud of dust and gas, while a small scope will bring out its darker and lighter patches.
The constellation of Gemini, the Twins, borders Orion on the Hunter’s upper left shoulder. Gemini’s two prominent stars, Castor (Alpha (a) Geminorum) and Pollux (Beta (b) Geminorum) are easily found: follow an imaginary line from Rigel to Betelgeuse and keep going until you reach two prominent stars positioned one above the other. They each form one of the heads of the Twins, which at this time of the year look like they are lying down with their feet near Orion’s raised arm.
The Bull’s Eye
To find the next constellation use Orion’s Belt as a reference point again, and allow your gaze to drift upwards to the right of Orion’s shoulder. You’ll spot a bright orange star called Aldebaran (Alpha (a) Tauri), the brightest star in the constellation of Taurus, The Bull. Also known as the ‘Eye of Taurus’, this red giant is much cooler than our Sun. Taurus hosts two fantastic open star clusters and Aldebaran is positioned within one of them, the Hyades, which
appears like a ‘V’ shaped pattern of stars on its side. Located just above this is another cluster called the Pleaides (see picture, above), also known as the Seven Sisters because of the seven stars you can see with the naked eye. A pair of binoculars will reveal many more of the dimmer stars within each cluster.
The Bears and a Dragon
Continuing with the tour, find Gemini again and sweep your eyes to the north. They will settle upon two constellations which you may well have spotted before – Ursa Major, the Great Bear and Ursa Minor, the Little Bear, whose tail ends with the North Star, Polaris (Alpha (a) Ursae Minoris). Draco, the Dragon winds its way between them both. Visible all year, these constellations hold some surprising targets.
Ursa Major’s back and tail make up that familiar asterism the Plough. At the bend in the Plough’s handle lie Mizar (Zeta (z) Ursae Majoris) and Alcor (80 Ursae Majoris), a double star. Can you make them both out with your eyes alone? Mizar is brighter, so reach for your binoculars or scope if you struggle to see Alcor.