Apr 04

What’s Up in the Sky

What’s Up in the Sky – April, 2014

Ever Seen an Occultation?

When I began researching topics for this month’s column, I was excited to see that there will be a total lunar eclipse this month. Unfortunately, you will have to stay up past 4 a.m. in order to witness the whole thing. Not to worry, though, as Mars will put on quite a show and the Moon will occult (pass in front of) several stars. Now, if we can get some clear weather, this could be a good month.

Astronomical observations do not have to be complicated or require expensive equipment. Some of the best events I have observed have been with the naked eye or binoculars and we will have just such an opportunity on the evening of Thursday, April 3. On that date the Moon will pass in front of (occult) several fairly bright stars in the Hyades star cluster.

On the plus side this occultation takes place at a good time and the objects involved will be easy to find. On the minus side it happens near the horizon so we will need an unobstructed view and good weather. That being said, I strongly recommend the use of binoculars and a good clock. The binocs will help you see it and the clock will tell you when to look, which is pretty important.

Go out around 10 p.m. and look due west near the horizon. The crescent Moon should be easily visible between Orion on the left and the Pleiades on the right. Right next to the Moon you should spot a V-shaped group of about five or six stars. Now watch as the Moon approaches the stars, getting closer and closer until, at about 10:15, the star will disappear behind the unlit side of the Moon.

There are two things I like about this observation. First, you are seeing two apparent motions of the Moon – it moves closer to the horizon due to the rotation of the Earth and it gets closer to the star cluster due to its own orbital motion around the Earth. Second, as the separation between the star and Moon decreases, it becomes possible to actually witness the Moon’s motion with respect to the background stars – not an easy thing to see usually.

As for the lunar eclipse, if you plan to be up all night on the 14th, definitely check it out. And yes, Mars is close this month and up all night, but it is only well placed for viewing after midnight. It will be earlier next month.

So this month, the lunar occultation will be your best chance to enjoy what’s up in the sky.

This month in history:
April 2: First photograph of Sun taken – 1845
April 12: Yuri Gagarin becomes first human in space – 1961
April 12: Columbia is first space shuttle to be launched – 1981
April 17: Apollo 13 returns to Earth – 1970
April 20: Shapley-Curtis debate on the distance and nature of spiral nebulae – 1920
April 25: Deployment of Hubble Space Telescope – 1990