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This month we wheel through the southern limits of Auriga, the Charioteer
Tick the box when you’ve seen each one
1 M37
The misshapen pentagonal form of Auriga, the Charioteer, plays host to some excellent deep-sky objects, the most famous being three open clusters of the Messier catalogue, all of which are found in the constellation’s southern region. Mag. +5.6 M37 is our first target; it can be found almost 5º south and fractionally west of mag. +2.7 Theta (e) Aurigae. It’s a rich open cluster and a great target for smaller instruments. Use a low power and then gradually increase the magnification until you get to the most pleasing view. The cluster contains around 150 stars down to 12th magnitude, grouped into a region approximately 20 arcminutes across. A red 9th-magnitude star shines out from the centre. This cluster is 4,400 lightyears from Earth. SEEN IT
2 M36
M36, the Pinwheel Cluster, is 3.75º west-northwest of M37. Visually it is less impressive than M37, having fewer members and – occupying an area approximately 12 arcminutes across – being roughly half its size. Despite this it’s still a lovely sight through a small instrument, with a 6-inch scope bringing approximately 60 stars into view. A good number of these are blue-white in colour and bright, at around the mag. +9.0 mark. Outlying stars appear to create an almost cruciform shape, with the intersection of the cross falling at the cluster’s core. M36 is 4,100 lightyears and shines at mag. +6.3, just below the threshold of naked-eye visibility. SEEN IT
3 M38
At mag. +7.4, M38 is fainter than its two Messier stablemates, but its 21-arcminute apparent diameter is comparable with that of M37. The cluster is 2.3º northwest of M36 and appears quite loose. It has a very irregular outline and is heavily peppered with 10th- and 11th-magnitude member stars. Look out for the fainter and smaller open cluster NGC 1907, just 0.5º to the south of M38. It has a magnitude of +8.2 and appears 6 arcminutes across, approximately one-third the size of its larger neighbour. NGC 1907 is 4,500 lightyears away and is estimated to be 500 million years old. In comparison, M38 is a youngster, being 200 million years old and lying 4,200 lightyears away. SEEN IT
4 NGC 1931
Mag. +11.7 NGC 1931 is located approximately 1º west of M36. This is a cluster with a surrounding nebula made up of reflection and emission components. The presence of tightly packed stars at the heart of the emission section have drawn parallels with the Trapezium Cluster at the heart of M42, and NGC 1931 is sometimes described as a miniature Orion Nebula. The nebula stretches to 3 arcminutes, although most views show it to be elongated and roughly half this size. A large patch of diffuse nebulosity known as IC 417 sits 42 arcminutes to the west. In long-exposure images they are collectively termed the ‘Spider and the Fly’, NGC 1931 being the fly. SEEN IT
5 IC 405
IC 405, the Flaming Star Nebula, is a popular target for astro imagers, but a tricky object to glimpse visually. It is 3.1º to the west of NGC 1931 and surrounds 6th-magnitude AE Aurigae, a runaway star ejected from the Trapezium Cluster in M42 some two million years ago. AE Aurigae isn’t associated with the nebula, but passing through it at high speed. As it does this a bow shock from the interaction produces the energy required to make the nebula glow. A transparent night is required to see anything of IC 405. Use a low power eyepiece and, with properly dark-adapted eyes, the Flaming Star Nebula should appear as a weak, curving glow. SEEN IT
6 .2+287(.
Kohoutek 2-1 is a mag. +13.8 planetary nebula close to the border of Auriga and Taurus. Imagine a line between mag. +1.7 Elnath (Beta (`) Tauri) and mag. +2.7 Hassaleh (Iota (f) Aurigae). Look southwest of the line’s midpoint to find two stars of around mag. +6.6, then extend the line between them west. You will reach a pair of 9thmagnitude stars; the planetary nebula is 3 arcminutes northeast of the northern star. Unusually, a low power works better than a high power here. An OIII filter will also help. The nebula has a diameter of 2.2 arcminutes and should appear as a circular glow. Sections of its edge appear brighter, giving the overall appearance of a pair of brackets enclosing the inner glow. SEEN IT