Apr 01

April 2006

Whats Up in the Sky April, 2006

Moon Occults Pleiades

As I write this, we have had several clear nights in a row – unusual for late March in West Michigan. Hopefully April will offer more clear nights for there is much to see in this months sky.

We start off with a bang next Saturday when the Moons motion in its orbit brings it directly between us and the star cluster M45, also known as the Pleiades, blocking the stars from our view as it moves past them.

Astronomers call this an occultation, or we say that the Moon will occult the stars.

Go out around 7:30 p.m., face west and look for a thin crescent Moon, about half way up from the horizon to overhead. You should be able to see the dark side of the Moon illuminated by sunlight reflected off the earth (called Earthshine). As the sky darkens, you will see that the Moon is in front of a small cluster of stars, called the Pleiades, the cluster itself being about twice as wide as the Moon.

With binoculars or a small telescope over the next two hours, you will be able to see several stars in the cluster disappear behind the unlit side of the moon and reappear from behind the crescent about an hour later. You will have then actually observed the moons motion in space.

I highly recommend that you mark this event on your calendar. In April, 1979, I witnessed the moon occult the star Aldebaran, the bright star just to the left of the Pleiades. As with this month, this happened just after sunset with a thin crescent moon. I was at a gathering in Kalamazoo with about 30 people and I was only able to convince one other person to come outside with me to watch it. A common reaction from many was, “so what, that must happen all the time.

I have never seen another occultation like that one. I was amazed at how the star just instantly disappeared. And, no, it does not happen very often. The Moon does occult stars periodically, but most of the time it happens when we can’t see it. Either the Moon is below the horizon, or its daytime, or the star is too dim, for example. So to have the crescent Moon pass directly in front of a cluster of stars in the evening on a Saturday in April, is a unique opportunity that should not be missed.

Here are this months viewing highlights:
Planets this month: Mars is high in the SW to W after sunset, Saturn shines high in the south. Predawn skies are dominated by Jupiter in the SW and Venus in the SE. Mercury is to the lower left of Venus about 30 min. before sunrise, but is difficult to see.

April 1: Crescent moon occults Plieades
April 5: First-quarter Moon
April 6: Saturn right below Moon in SW, Beehive cluster nearby – great viewing opportunity for a small telescope.
April 8: Try to spot Mercury low on the eastern horizon around 6 a.m.
April 18: Use binoculars or a small telescope to find Uranus about one-half moon diameter below Venus in the east at 5 a.m.
April 13: Full Moon
April 14: Moon and Jupiter rise together 2 hours after sunset.
April 15-17: Binoculars or a small telescope offers the best way to see Mars move past the open star cluster M35 in Gemini.
April 20: Last-quarter Moon.
April 24: Crescent Moon just to the right of Venus, one hour before sunrise.
April 27: New Moon

Peter Burkey – SAAA President