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Articles: Auriga, the Charioteer

By Michael O'Connell, MAC

As you look high towards the southeast at this time of year, you’ll see a constellation that looks like a five-sided figure. This is the constellation of Auriga and is sandwiched between Gemini, which we covered in the previous issue of Réalta, and Perseus. From ancient mythology, Auriga was considered to represent either a shepherd or more commonly, a charioteer. The ancient Greeks identified it as Erichthonius, a legendary ruler of Athens who reportedly suffered from lameness. As a means to get around he developed the chariot and became a legendary charioteer.

 

Stars

The brightest star in Auriga is Capella, a Aur. This is instantly recognisable as a bright yellow star at the top of Auriga. This star is 42 light years from Earth and is a spectroscopic binary with stars orbiting each other once every 104 days.

The next brightest star in Auriga is Menkalinan, b Aur. It is located to the lower left of Capella and is the most eastern star in the famous five-sided figure. Menkalinan is an eclipsing variable star of magnitude 1.9. It consists of two stars that orbit each other every 4 days, making them too close to be seen through the average telescope.
Following around the five-sided figure we come to q (Theta) Aur. This star looks a little bluey-white in colour. When looking through a telescope, you might just about be able to make out the mag. 7.1 companion star.

One star that causes some confusion is the star Elnath, g Aur. It is the star in the lower left corner of Auriga. Although part of Auriga, it is often shown as part of the constellation Taurus. In fact, it is also officially called b Tau making it one of, if not, the only star that forms part of two constellations!

About 7 degrees to the upper right of Elnath is the star Hassaleh, i Aur which completes the pentagon shape. Hassaleh is a red giant star and is located 513 light years from us.

 

Deep Sky

Auriga has a few lovely deep sky objects that are well within reach of binoculars or even the naked eye if you observe from a dark site. The first of these we’ll deal with is M36. This object is an open cluster located approximately 4,000 light years from Earth. It is actually a young cluster and thus has no old red giant stars in it. To find M36, point your binos midway between the two stars forming the “base” of Auriga. Then, look out for a small diffuse object which is near the top of your view. You should see M36 completely surrounded by thousands of stars which fill up the entire field of view. These stars are actually part of the Milky Way, which makes Auriga one of my favourite targets for binoculars. With a small scope, the stars in M36 start begin to resolve themselves. When looking at M36, can you imagine a shape from the arrangement of stars? Various astronomers have described seeing shapes ranging from a crab to a rocking chair! Personally, when I look at M36 at 75x I see the figure of a person with outstretched arms on each side. Take a look for yourself and let me know what you see.

Next up is M37. This stellar object is probably the brightest of all the deep sky objects in Auriga. It can be found in the same field of view as M36 when using a pair of binos. M37 is located approximately 4,300 light years from us and contains around 150 stars. With a steady pair of binoculars, you might be able to distinguish a few stars in this open cluster. Can’t hurt to give it a try. In a telescope, M37 is simply spectacular! At about 75x it takes up almost the entire field of view and resembles fine grains of sugar sprinkled on a black cloth. Just off-centre, your eye will be automatically drawn to the brightest star in the cluster which appears distinctly orange. This star is mag. 9.2 and is one of about a dozen red giants in this cluster. The presence of red giant stars indicates that M37 is significantly older than M36. When viewing M37 in a telescope, keep an eye out for a small dark lane or star-free patch near the orange star. See it? This is a cloud of gas and dust within our own galaxy, The Milky Way, which blocks distant starlight from reaching our retinas. Earlier, I mentioned making patterns from the stars – Lord Rosse thought M37 had “wonderful loops and curved lines of stars”. What do you see?

The final Messier object in Auriga is M38. Again, this is an open cluster and is also about 4,000 light years away. To find M38, “hop” from M37 up to M36 and about the same distance beyond is M38. Like M37, this cluster is approximately 25 light years in diameter, which incidentally is nearly twice the size of M36. M38 again seems to from various patterns depending on the observer. Incidentally, these patterns are obviously not real as such – it’s just a natural reaction of the human mind to try and distinguish a familiar shape from a random pattern. M38 is often considered to resemble a cross. Stephen James O’Meara reckons this cluster looks like a cross with a little circle near its centre in which a single star lies. To be honest, I see more of a boat – a triangle of stars to form the hull and a row of stars (probably the “leg” of O’Meara’s cross) to form the mast. At low power, it looks like a ship sailing amongst the stars. However, each person is different and might see a completely different shape. Only way to find out it to take a look.

Finally, to test your telescope and observing skills, try and take a look at the Flaming Star Nebula, IC 405. This nebula surrounds a mag. six star about 2.5 degrees to the right of M38. Binoculars or a small telescope will easily reveal the central star. However, with larger telescopes a nebula can be seen with adverted vision. Due to the brightness of the central star, it’s difficult for the eye to detect the fainter nebula surrounding he when looking straight on. It’s only when you look away from the star, the nebula jumps into view as a smokey cloud surrounding the star.

 

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