Moon and Pleiades In astronomy, an occultation is when one closer object passes in front of another farther object. Most commonly, our Moon is the closer object and a star or planet is the more distant one.

Tomorrow night (October 9 in the US) you’ll get to see this phenomena for yourself. Starting around 11pm CDT (4am GMT on the 10th) the nearly full Moon will pass in front of the Pleiades star cluster (Messier 45) in the constellation of Taurus. The stars of this cluster will disappear behind the bright edge of the Moon and reappear later from the dark edge.

Because of the brightness of the Moon you’ll need binoculars or a small telescope to see this best. It’s rather amazing to see the stars pop out almost instaniously from behind the dark limb.

At my location the Moon will rise around 8PM so it will be well above the eastern horizon by the time the occultations begin. You can check your local paper for the time of Moonrise in your area. If you click on the thumbnail you can see a timeline of the Moon’s position relative to the star cluster. This chart is only strictly valid for my location (Central Iowa). If you want to get accurate information for your own location you can go to this link for details. Otherwise, just go out and look up at the sky around the times indicated (adjusted for your time zone.)

4 comments on “Occultation

  1. Sounds like you are going to be busy later in the evening tomorrow night so I better call you early from Chicago. In some ways, I’m kind of sad that I won’t be here to see it.