Chariot of the Sky
Auriga the Charioteer rides high across the northern winter sky these nights. This is a wide-field image I took last week of the constellation that now shines overhead from northern latitudes.
My image takes in all of Auriga, the pentagon-shaped charioteer of Roman mythology, as well as the feet of Gemini the twins, spanning a wide area of the winter Milky Way. Sprinkled along this bit of Milky Way you can see a few clusters of stars. They include four of the best open star clusters in the catalogue of Charles Messier: M35 in Gemini at bottom, and M36, M37 and M38 in Auriga at centre, all wonderful targets for a small telescope. Some of these targets lie in the next spiral arm out from the one we live in.
The star colours show up nicely here, with the brightest star at top appearing a little off white. That’s Capella, 42 light years away and classified as a type G “yellow” star not unlike our own Sun in temperature but much larger – a giant star. Indeed, it is really two yellow-giant stars in close orbit around each other. It’s interesting that Capella doesn’t really show up as yellow. Just like our Sun does to our eyes, Capella appears white because it still emits such a broad range of colours that even though its peak energy does fall in the yellow part of the spectrum, all the other colours remain strong enough that the star looks white to our eyes. Remember, our eyes evolved under the light of a type G star to see all the colours of the spectrum from red to blue.
Only the cool red giant stars take on a yellow or orange hue to our eyes, and to the camera. You can see a few in this image, as well as hot blue stars. The pinky red bits are nebulas in the Milky Way – clouds of hydrogen gas emitting deep red light.
When we look in this direction in the Milky Way we are looking out toward the edge of our Galaxy, exactly opposite the galactic centre.
– Alan, February 21, 2012 / © 2012 Alan Dyer