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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.
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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.
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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 300º
and separation 3.6".
Omega Aurigae: 5.0, 8.0; PA 360º, separation 5.4".
14 Aurigae is a multiple double, visible in larger scopes.
The primary is 5.1, with three companions: B (11.1, 352º, 11"),
C (7.4, 225º, 15") and D (10.4, 356º, 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.
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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.
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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.
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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.
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To find M36, move west just across an imaginary line from El Nath to theta Aurigae.
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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.
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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.
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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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