Moon and Antares

StarDate

You don’t have to be an astronaut to see the far side of the Moon – at least some of it. A little bit of that hemisphere wobbles into view every month – an effect known as “libration.” So we can actually see 59 percent of the lunar surface.

The Moon is “locked” in such a way that the same hemisphere always faces Earth. That means we see the same features all the time – the same dark volcanic plains, and the same lighter-colored jumbles of mountains, valleys, and craters. Almost.

As the Moon orbits Earth, we get some peeks at the other hemisphere – the far side. The Moon is tilted a bit on its axis, for example. So as it orbits Earth, it appears to “nod” up and down a bit – just as Earth appears to nod as seen from the Sun. That allows us to see just beyond the north and south poles.

Also, the Moon’s distance from Earth isn’t constant – it varies by almost 30,000 miles. As a result, the Moon’s orbital speed goes up and down. But the rate at which the Moon spins on its axis remains constant. That allows us to see a little bit around the eastern and western edges – glimpses of a little bit of the lunar farside.

As darkness falls this evening, we’ll see a little bit beyond the north pole. We’ll also see a little bit beyond the western limb – or would if that part of the lunar disk weren’t in darkness. As a bonus, the Moon has a close companion: Antares, the bright heart of the scorpion.

Script by Damond Benningfield