Astronomical Potpourri in March

I began writing this column on Groundhog Day, February 2, 2011. The Inner Circle organizers in Punxsutawney, Pennsylvania, wrestled Phil out of his temporary cozy burrow at 7:25 am at Gobbler’s Knob to forecast the return of spring. Though this famous groundhog did not see his shadow, supposedly indicating an early spring, astronomically speaking winter will last until the vernal equinox on March 20 at 7:21 pm. Though I do not believe in Phil’s folklore-ish abilities, I do hope his prognostication proves true for southern New England. Because at this time I’ve got over 40 inches of snow in my front yard.

The local observatories have been closed not only due to the adverse weather conditions on an open night, but also due to the amount of snow and ice making the grounds inaccessible. This observing deprivation could possibly result in a new definition for March Madness!

We can only hope that March winds will be calm with clear skies and almost snow-free grounds. Then all stargazers will once again be able to enjoy the beauty of the heavens. March skies will present several astronomical events of interest.

For those of you who travel east to work before sunrise have had a very bright companion on your travels in recent months…Venus. You must have noticed that as time has passed Venus has been moving closer to the eastern horizon. Each day it will rise a little earlier. By month’s end it will be very low above the eastern horizon around one hour before sunrise. Very soon thereafter it will be too close to the Sun to be seen and will move into the evening sky after sunset in April. Then it will be your traveling companion as you drive home.

Also in March you should notice brilliant Jupiter moving closer towards the western horizon after sunset as the month progresses. While we’ll lose sight of it by April, Jupiter will share the western sky with some other celestial bodies before it disappears. About one-half hour after sunset on March 6, a very thin crescent Moon will be located to the upper right of Jupiter. It should be a very beautiful sky scene, and I’d encourage you to take an image of it.

During the next couple of weeks Mercury will rise high enough above the western horizon to be easily observed. However, you’ll need an unobstructed view. Mercury will first appear to the lower right of Jupiter within a half hour after sunset around the 10th. Each night it will rise higher into the sky, moving ever closer to Jupiter. They are closest on the 14/15th. Mercury will continue to climb past Jupiter, while Jupiter itself will be moving closer to the horizon.

If you have a telescope you can watch Mercury go through phases like our Moon. Because of its orbit about the Sun and our observing position here on the Earth, the image size of Mercury will increase and the phase of illumination will decrease.

For example, on March 8 it will be 90 percent illuminated and by the 22nd will be just under 50 percent lit. Its apparent size will continue to grow as it approaches the Earth, and the phase will shrink. Unfortunately it will then be moving closer to the western horizon each night, making it more difficult to observe. It becomes a 25 percent lit crescent on the 27th. Try to catch a glimpse of Mercury, even if it is just with binoculars, for this is the hellish world’s best appearance all year.

Don’t forget that most of the United States switches over to Eastern Daylight Time (EDT) or Daylight Saving Time (DST) on Sunday, March 13. That’s when we set the clocks ahead one hour at 2:00 am. While this action is not astronomical in nature, it does affect observers of astronomical events.

Astronomers use Coordinated Universal Time (UTC), also known as Greenwich Mean Time (GMT), as a standard. And most astronomical almanacs provide UTC when announcing the date and time of an event. It is up to the observer to convert for the local time zone. We are in the Eastern time zone, so when EST is in effect, UTC is ahead of us by five hours. During DST that difference is only four hours. If you forget to convert you will most likely miss an event.

As briefly mentioned earlier, an important event occurs on Sunday, March 20 at 7:21 pm – the vernal equinox or the beginning of spring. Because of the Earth’s tilt upon its axis as it orbits the Sun, our life-giving star appears to move north or south in our sky throughout the year. During the Northern Hemisphere winter the Sun moves across the southern sky in a low arc. After the winter solstice on December 20/21, the Sun appears to move north. When it crosses the celestial equator (an imaginary line in the sky representing the extension of the Earth’s equator into space) on its way north, this is called the vernal equinox. Day and night are of equal length. It will continue its apparent journey northward in our sky until the summer solstice on or about June 20/21. The Sun will then be at its highest point in our sky.

And finally, Saturn rises about 8:20 pm during the beginning of March. It is easily accessible to folks with a good eastern horizon an hour or two later. However, if you can wait until April (when hopefully all the snow will be gone), this beautiful ringed-planet will rise earlier so you can observe it earlier. Besides, I’ll provide a Saturn observing guide in next month’s column.

Don’t forget that Seagrave Memorial Observatory (http:/www.theskyscrapers.org) on Peeptoad Road in North Scituate is open every clear Saturday night for public viewing, provided the skies are clear and the property is accessible. With the change to DST during March, the open hours will change after March 13 from 7:00-9:00 pm to 8:00-10:00 pm. In addition, Ladd Observatory (http://www.brown.edu/Departments/Physics/Ladd/) in Providence is open every clear Tuesday night, weather permitting as well. Ladd’s hours of operation will also change from 7:00-9:00 pm to 8:00-10:00 pm after DST is implemented. Please check their respective websites for any cancellation notices before venturing out for a visit.

Keep your eyes to the skies.