Moon and Saturn in the Skies this Week

There are two things worth watching in the sky this week. Saturn is at opposition and the Moon passes very close to the Pleiades star cluster.

Although the Moon will be in the night sky most of the week, on Monday, around 10pm, the Moon will pass very close to the Pleiades. Above and to the right of Orion is the constellation Taurus the Bull. The brightest star in Taurus is Aldebaran, but you'll also notice that there is a little group of six stars so close together you could cover them with your fist held at arm's length. This is the Pleiades star cluster and these are, astronomically speaking, very young stars. Just below the Pleiades is another open cluster called the Hyades, they aren't as obvious as the Pleiades because they are more scattered, but they are also part of Taurus.

While we're on the topic of the Moon, I recently had a question asking how much of the Moon's surface we can see from Earth. Most people seem to think that we can either see all of the Moon, as it rotates, or that we can see fifty percent of the Moon's surface. Neither are correct.

The Moon is gravitationally locked in it's orbit around the Earth and it does keep the same face towards us for the most part. But there's another motion going on here that allows us to see just a bit of the Moon's far eastern and western limbs. It's called libration, a slight swinging motion that happens because the moon's orbit around Earth isn't a perfect circle, but rather an ellipse. An elliptical orbit means that the Moon travels a little faster in it's orbit when it is closest to Earth. But the Moon's rate of spin does not change and so it's orbital motion and it's rotation get slightly out of synch, allowing us these extra glimpses of the Moon's far edges. In all, we get to see about fifty-nine percent of the Moon's surface along those eastern and western limbs. To the unaided eye, it doesn't make any difference to how the Moon appears to the naked eye, but binoculars or a telescope will allow you to see these extra areas, which include some very nice craters.

On Tuesday, Saturn is at opposition. This means that the Earth passes directly in between Saturn and the Sun. It also means that Saturn rises in the east after sunset and is in the sky all night long. Look for Saturn just above Orion's arm, towards and above Gemini.

Saturn is in a great position for viewing once it gets further up in the sky. Binoculars or a small telescope will show Saturn's rings, which are in a great position for viewing. Saturn's rings appear at various angles to us, sometimes edge on and barely visible and other times at a perfect angle, like right now. And while you have those binoculars or telescope out, look at the fuzzy patch below the middle belt star in Orion. This is the Orion nebula, a place where stars are being born. Happy Stargazing!

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