Auriga

Auriga


Transit Date of principal star:
10 December


Auriga is an ancient Northern Hemisphere constellation featuring one of the brightest stars in the heavens: Capella. Auriga is usually pictured as a charioteer; the youth Auriga wields a whip in one hand and holds a goat (Capella) and her two kids in the other.

Capella means "small goat". A previous name of this star was Amalthea, which was the goat that suckled the baby Zeus. There are many ancient stories relating to the star, as every culture in antiquity found a place for this bright companion to Taurus, its closest neighbour.
To find Auriga, first locate Orion. Taurus is to the right (west) and just above these two, much higher in the sky, you will see Capella. While this star marks roughly the mid-point of the constellation, north to south, most of the more interesting aspects of the constellation are found to the south of the star, all the way down to El Nath, the second brightest star (gamma Aurigae) which is actually shared with Taurus, and also known as beta Tauri.

Auriga's stars are fairly bright; five are second magnitude or brighter. Alpha Aurigae (Capella) is the sixth brightness star, at a visual magnitude of 0.08. The star is 43.5 light years away, and is about ten times the size of our Sun.

Capella's visual magnitude is really the combined brightnesses of the primary star and a close companion, that revolves every 104 days. There is another companion, much fainter: a red dwarf which is itself a close binary.

Binary stars in Auriga.

Zeta Aurigae is an eclipsing binary; an orange giant primary with a blue companion that orbits every 972 days (2.7 years).

Theta Aurigae is visible in large scopes: 2.6, 7.1; PA 300 and separation 3.6".

Omega Aurigae: 5.0, 8.0; PA 360, separation 5.4".

14 Aurigae is a multiple double, visible in larger scopes.

The primary is 5.1, with three companions: B (11.1, 352, 11"), C (7.4, 225, 15") and D (10.4, 356, 7.7").


Variable stars in Auriga

There are a half-dozen variable stars in this constellation which are visible in small scopes, most of them of very small variance.
Epsilon Aurigae is an unusual variable which normally maintains a visual magnitude of 2.92 but every 9892 days (27 years) dips down to 3.83.

The next scheduled dip is in the late summer of 2010. The eclipse phase lasts about a year.

R Aurigae is the only Mira-type variable of interest. Normally a rather faint 6.7, every 457.5 days it takes a nose-dive to 13.9. The best time to view this feature is in late November of 2001, when it should be near the transit.


Deep Sky Objects

Auriga has three Messier objects: M36, M37, and M38. A telescope is preferred but you can at least locate these objects with binoculars.

M36 is a rather faint cluster of about 50 to 60 stars, in a very compact area. A large scope is necessary to resolve the individual stars.

To find M36, move west just across an imaginary line from El Nath to theta Aurigae.

M37 is the most spectacular of the three Messiers, and also the most easily found, as it lies midway between El Nath and theta Aurigae.

This last star is to the east of El Nath and north, about half way up to Capella. Now slightly to the east of an imaginary line between these two stars, and half way along that line, is M37, a rich star cluster of perhaps 150 stars.

Binoculars will only show a fuzzy mess; you really need a scope for this one. A medium sized scope should reveal at least twelve red giants, with the brightest one found at the centre of the cluster. Some observers find this star more orange than red. What do you think? In any case, it's a sight worth seeing. The cluster is considered to be about 200 million years old.

M38 is in the same field, just to the NW of M36. Some observers have described this cluster of about a hundred stars as having a cross-shape.

For a closer appreciation of Auriga, visit the Binocular Section.


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