I threw in an early teaser this week to make sure I gave enough lead time on the Aldebaran occultation, so this week’s “regular” post will be a short one. (The occultation, though brief, was really cool to watch – things in a small telescope are always moving, the Earth’s rotation pushing things out of frame. But I got a view of part of the bright half of the Moon, the terminator, and the dark limb, with the star just outside the dark moon, which was still visible from Earthshine. As the distance between the Moon and Aldebaran got smaller, you could actually SEE the Moon moving across the sky. The closure rate was obvious, until Aldebaran winked out in an other-worldly sunset. Really neat to see!)
This week, the Moon is progressing through the southern sky, and Venus is starting to accelerate toward the sun (you can almost see its movement night by night now). So while we have a relatively quiet week, here’s a quick primer on star orientation using the Big Dipper as a guide.
First of all, find the dipper in the northeast. It is standing on its handle (the tail of the Great Bear, Ursa Major) just after sunset. Most of you probably know (and I’ve mentioned), the two stars on the end of the dipper are the pointers. Follow the line they describe to the left and they Point to Polaris, the North Star.
Follow them backward, the other way, and you Land in Leo. Follow the curve of the handle and Arc to Arcturus, the bright star in the constellation Bootes. From there you can continue and Spike to Spica, in Virgo. Arcturus is low in the east, and Spica still below the horizon until later at night, so you may have to try this latter part again later in the year. (BTW, Jupiter is in Virgo right now, I’m looking forward to having that visible before midnight…)
Back to the dipper: start with the star where the handle attaches to the bowl, and stretch a line diagonally across the bowl. This line will Go to Gemini.
And finally, starting with that same star at the handle and trace a line across the top of the dipper’s bowl, and you Crash into Capella.
(Thanks to the fine folks at “Sky and Telescope” magazine for reminders of these little mnemonics!)
Capella is the bright star high overhead in the constellation Auriga. We haven’t talked about this one yet so a quick intro – forming a large pentagon shape with Capella in the upper right , Auriga is the “charioteer”, but the legends are a bit mixed, and he’s often depicted carrying a goat and two baby goats. This goat is supposed to be Amalthea, the animal that fed the infant Zeus in Greek mythology. Capella is therefore also called “the Goat Star”, and the two smaller stars just beneath it are “the Kids”.
If you’ve been following along with me for two months now, you ought to be able to piece together a pretty good map of the winter sky by this point. New constellations are coming, along with Jupiter, Saturn, a few meteor showers, more comets…
Get Out There!