Auriga

by Shaphan Shank | Feb 9, 2022 | 0 comments

IC 405, Flaming Star Nebula
IC 405, the Flaming Star Nebula, is an emission/reflection nebula in Auriga. While beautiful in photographs, it is quite faint and difficult to visually observe. Photo © Shaphan Shank.

Auriga is not quite as well-known as Orion or the Big Dipper, but it is quite easy to find, due to its bright stars. Auriga is basically a slightly oblong circle of stars located straight north of Orion. Its brightest star Capella is brighter than any of Orion’s stars.

Auriga contains a number of open star clusters; the best three are M36, M37, and M38. These three clusters are similar in size and brightness, and are arranged in a line about 6° long. All three clusters are visible with binoculars, and at least two of the three can be seen in the same binocular field of view.

M38 lies just south of the center of Auriga’s outline. Many observers see a cross or “X” shape in this cluster. NGC 1907, a much smaller cluster, is ½° south-southwest of M38. The two clusters can be seen in the same telescopic field of view at lower magnifications.

M36, the next of the three star clusters, is just over 2° southeast of M38. M36 is a little smaller and contains fewer stars than M37 and M38, but it stands out well from the background stars and is still a nice cluster.

M37 lies just outside the outline of Auriga’s stars; it is almost 4° southeast of M36. M37 is the richest and most impressive of the three Messier clusters in Auriga. A bright orange star is near the center of the cluster.

UU Aurigae is a carbon star in the eastern part of Auriga. Carbon stars are cool (relatively speaking) variable stars that contain a lot of carbon in their outer layers. This carbon scatters shorter wavelengths of light, while allowing longer wavelengths such as yellow and red to pass through. As a result, carbon stars are often some shade of orange or red.

UU Aur is not as red as some carbon stars, but is a pretty deep orange. It varies from magnitude 5 (dim, but visible to the unaided eye) to magnitude 7 (visible with a binocular). Although UU Aur is visible without optical aid during its maxima, you will probably see more color in this star if you use a telescope at low magnification. UU Aur is about 7½° east-northeast of Theta Aur.

Just ½° southwest of UU Aur is Otto Struve 147 (abbreviated as STT 147), a beautiful triple star with the component stars in a nearly-equilateral triangle. The component stars are widely separated, so low magnification will give the best view of this triple. The star at one point of the triangle is bright and yellow, while the other two are fainter and blue-white. At low magnification, this triple star and UU Aur both fit in the field of view.

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