Feature Article April 10, 2003
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Night Skies - A great chance to see the Planet Mercuryby Leo EnrightAt the beginning of April our sunsets were at about 7:30 p.m. EDT, but by the end of the month they will be a little after 8:00 p.m. EDT - a change of about 1 minute per day. The end of twilight time changes by more than a minute per day - from 9:15 p.m. EDT at the first of the month to about 10:00 p.m. at months end. In the mornings, sunrise times are progressively earlier by almost 2 minutes per day, moving from about 6:50 a.m. EDT on April 1 to 6:00 a.m. on April 30.
The winter star patterns of Orion, Taurus, and Canis Major are now sinking low into the western sky as evening twilight turns to darkness. Replacing them we have the constellations of the spring evening sky. High in the south we have Leo, the Lion, with its large backwards question mark of stars outlining the head and forepaws of this large jungle beast, and with the brilliant star Regulus marking one front paw. An equally distinctive triangle of stars outlines the hindquarters of the westward-facing lion. To his left, and down into the southeastern sky, is Virgo, the Maiden, marked by the very bright star, Spica. Further downward and to her left, in fact, fairly close to the south-eastern horizon, is the box-like pattern of four stars known as Libra, the Scales. Within the areas of these three large constellations, careful observers with binoculars and small telescopes can spend hours finding and studying very distant galaxies, and also many very interesting variable stars within our own galaxy.
For observers who enjoy watching the wonders of the sky with the unaided eye, this month provides the best chance in a long time to have an extended look at the planet that is seen most rarely, namely Mercury. Mercurys cycle over the years is such that it regularly appears for only a short period, such as a couple of weeks, three times a year low in the western evening sky and three times a year low in the eastern morning sky. However, this month, given clear skies, it should be possible to see this bright planet every single night during the month of April! Be sure that you have a good view of the western sky right down to the horizon, with no trees interfering, and start looking low in the western sky about a half-hour after sunset. Before long, Mercury should pop into view, above the horizon by about the width of a fist held at arms length. If you look at the same time and in the same place each night, you will notice that this planet appears slightly higher at mid-month and slightly lower later in the month.
After you have located Mercury, it will be easy to see two other planets in the evening twilight: firstly, Jupiter which is very high in the south-western sky, and by far the brightest object in a moonless evening sky, and the planet Saturn which is in the west about half-way between Jupiter and the western horizon. The other two bright planets are seen in the morning sky. Reddish Mars, now brighter than it has been for the past several months, rises about 2:00 a.m. and may be seen low in the south-east until morning twilight. Venus, the brightest planet of all, is now seen low in the eastern sky for about an hour or so starting with the beginning of morning twilight.
There are several lunar conjunctions worth viewing this month. On April 10, the waxing gibbous moon will appear just to the right of Jupiter. Remember, as you watch the Full Moon rise on the evening of April 16 that this is the Easter Full Moon, the one that determines the date of Easter in our calendar. It is the first Full Moon following the Vernal Equinox, and Easter is always the following Sunday. In the early morning of April 23, the Last Quarter Moon is just below Mars in the eastern sky. On the morning of April 28, try to see a very thin lunar crescent down and to the right from brilliant Venus in the eastern twilight; you will need a good eastern horizon for this one.
This is the month for the annual Lyrid Meteor Shower, and based on the numbers of shooting stars seen per hour in past years, it may be well worthwhile to stay up late for a couple of nights this month. This shower is active from April 16 to 25 with the peak nights being April 22 and 23. I would be interested in hearing about numbers of meteors seen per hour from those who observe between 10:00 p.m. and 2:00 a.m. on either of those two nights. These meteors are most likely to be seen in the eastern half of the sky.
Two special weeks are Dark Sky Week and Astronomy Week. Astronomy Week will be in May, and I intend to mention it in the next column. Dark Sky Week is this week, and it is designed to make people aware of the problems of light pollution in the night sky and of the harm it causes to our environment and the well-being of birds and other wildlife, as well as to the viewing and scientific study of natures celestial wonders. Visit http://nationaldarkskyweek.htmlplanet.com.
An adult interest course in astronomy relating to the spring and summer sky is planned for Algonquin College in Perth during May - a relaxing and practical way to learn the basics of the sky, in a course that is only one night a week. For more details, phone 267-2859 ext. 5620 as soon as possible. Observing information is also to be found in a book, The Beginners Observing Guide, available from Sharbot Lake Pharmacy. Clear skies and a very Happy Easter to all our readers!
