Observer's Notebook for March 1999

Dance of the Planets - Continued

by John Rummel

March in North America means the end of winter, with its long-awaited snow melt and milder temperatures. This year, March also gives us a chance to enjoy the continued dance of the planets, and a chance to bid farewell to Jupiter and Saturn until they reappear in the predawn sky later this summer.

During the first week of March, we are treated to a beautiful lineup of planets in the western sky just after sunset. Lowest in the sky are Jupiter and Mercury. Both will quickly fade into the glare of sunset over the next week.

Next up is Venus, climbing to its ascendancy as the evening star, and brighter than any other object in the sky other than the sun and moon. Finally, above brilliant Venus is Saturn. As spring nears, Venus will continue to climb and Saturn will slowly sink, and the two will see their closest approach on the 18th and 19th, just over 2 degrees apart (the width of your thumb at arm's length). The best view will be on the evening of the 19th when the thin crescent moon joins them a few degrees below. Look around 7 pm when the sun is well below the horizon.

This meeting of Venus and Saturn is not nearly as dramatic as Venus' near-miss with Jupiter last month. Saturn is not as bright as Jupiter, nor will it pass as close, but it will be the highlight of the month for backyard astronomers.

If you don't have to go to bed too early that night, come back out around 10:30 pm, and look in the eastern sky for Mars. The bright "star" just clearing the horizon is the red planet, making its first appearance in our evening skies since mid-1997. Don't mistake it for Spica, a first magnitude star about a hand's width to the upper right. Spica is very white, while Mars is unmistakably deep orange.

Mars is just one orbit further out from the Sun, and all spring Earth is rapidly overtaking it and will eventually pass it on April 24th (the so-called "opposition" date). Around that date, Mars makes its closest approach to Earth this year - just over 50 million miles. Thanks to Mars' eccentric orbit, it occasionally passes much closer to Earth. In August of 2003 the red planet will be just under 35 million miles distant.

You'll need a telescope to see any hint of a disk. Mars is only half the size of the Earth, and at this distance it will take very clear and steady skies, and high-power to see the any surface detail, such as the polar ice-caps. Have patience though, by late April, the apparent size of Mars' disk will gradually increase, making it an easier target for moderate telescopes.

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