The Moon and the Seven Sisters

The Moon and the Seven Sisters

The Moon and the Seven Sisters

Bad Astronomy
The entire universe in blog form
Nov. 12 2008 10:21 AM

The Moon and the Seven Sisters

The Moon orbits the Earth about once a month. As it does so, it sometimes passes directly over (occludes) bright stars and, rarely, planets. It's a fun event to observe, actually, to see the Moon encroach upon a star, getting ever closer, and then, blip! The star vanishes behind the Moon's limb. I've watched this dozens of times and it never gets old.

Sometimes, though, the Moon does itself one better. Or seven, actually: it passes in front of the Pleiades, a cluster of hundreds of stars in the constellation of Taurus. The Pleiades are a very tight formation, and only six or seven of the brightest members can be seen to the eye -- they form a shape that looks a lot like the Little Dipper, and are confused for that constellation by a lot of people.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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On Thursday, November 13, this will happen again. It starts around 16:00 UT and while it lasts for several hours, the timing means those of us in the US will miss it. It's best visible in Europe, and the northern parts of Africa and Asia. It happens again on December 11, but again misses the US. Nuts.

When the Moon passes through the Pleiades, it's pretty cool. They blip out one by one, some taking a direct hit, others barely missed by the Moon's disk. The whole thing takes roughly a couple of hours. And you can watch it from the safety of your computer: via the Royal Greenwich Observatory blog comes this very slick video of a Pleiadian occultation from December of 2006:


I love how the clouds dance in and out; it adds some drama to the short video. The Moon is actually smaller than it looks here; the overexposure makes it look bigger.

So if you are in the right place to see it, I suggest you take a look. Use binoculars so you can see the fainter stars more easily against the bright Moon. While it's not as spectacular as an eclipse or meteor shower, it's still an interesting event.