Mars and Venus partnered in heavenly dance

COFFEE WITH WARREN, with Warren Harbeck
Cochrane Eagle, April 17, 2002

Last week, coffee companion and astronomy commentator Bruce McCurdy introduced us to this week's promenade of the Moon and the five naked-eye planets visible in the evening sky.

Thanks to Bruce, I was quite taken with Sunday night's view of Jupiter, Saturn, Mars and Venus, and especially of the thin crescent moon as it slipped past Venus low in the west. (Mercury, at the time I was looking, had already set.) The shadow-side of the moon was dimly but distinctly visible, illuminated by Earthshine – sunlight reflected onto the Moon by the Earth. This phenomenon, sometimes known as "the old Moon in the New Moon's arms," is always awesome to behold.

But there's more awesome stuff to behold over the next few weeks, as Bruce explains in a further note:

ONE WOULD EXPECT the music of the spheres to be classical music, precise and majestic. But while the rhythms of the nearby spheres, our planetary neighbours, are individually tight and predictable (with an occasional retrograde flourish), as an ensemble they resemble free-form jazz.

Each seems to do its own thing without much regard for the others, one playing four beats to the bar, another five, another seven-and-a-quarter, or something. Suddenly they come together for a few bars and the music starts to make sense before they go their separate ways again. The planetary polyrhythms are presently at such a point.

Throughout the past winter, mighty Jupiter ruled the celestial dance floor, gleaming brilliantly high in the southern sky in the constellation of Gemini. It was accompanied by the ringed wonder, Saturn, in the neighbouring constellation of Taurus. The two have been passing acquaintances the past three winters as Jupiter in its smaller orbit has appeared to whiz by stately Saturn.

Jupiter's 12-year orbit can be easily tracked as it generally moves one zodiacal constellation to the east each year. Saturn takes thirty years to complete its own lap of the sky.

The outer planets set the pulse as they slowly circle the sky, the inner ones the melody as they flit back and forth.

Frequently two of them will come together in a planetary conjunction, more occasionally three; all five at once is exceptional. Under the current favourable circumstances, they will reward an observation on any clear evening, ideally an hour or so after sunset.

Mars, Venus, and Mercury, with their smaller orbits, faster speeds, and foreshortened viewing angles, are particularly interesting to follow.

And of course Viewing Platform Earth is moving, too. While we can't see Earth's orbital motion directly, it is reflected in the position of the Sun as we go around it. The five planets are all currently on the far side of the Sun; therefore all six appear to be going in the same direction -- east against the background stars.

In the upcoming weeks we will see the two inner planets, Mercury and Venus, pull away from the Sun, as the outer ones seem to fall towards it. It will be fascinating to watch them group together and overtake one another.

While Jupiter will continue to stand off to the east (upper left), the other four will conduct an elaborate square dance over the next three or four weeks.

Late in April, Mercury will join Venus, Mars and Saturn in the constellation of Taurus, with all but Saturn passing between the orange giant star Aldebaran on the left and the famous star cluster, the Pleiades, to the right.

The richly-studded star field provides a beautiful backdrop to the planetary dance, especially for those with binoculars.

Come May, first Mars, then Venus will appear to overtake Saturn. Then the famous pair will two-step through the evenings of May 9 and 10.

May 14 will offer a grand finale of sorts when the slender crescent Moon, holding the old Moon in its arms, sashays once more past brilliant Venus, as the fainter members of the planetary troupe fade into the sunset.

—Bruce McCurdy, Edmonton

BRUCE REMINDS ALL of us that this Saturday, April 20, is International Astronomy Day, a good time to explore the hobby of stargazing and to consider joining a chapter of the Royal Astronomical Society of Canada (

A coffee-cup toast to Bruce for helping the rest of us so thoroughly enjoy the celestial performance!

© 2002 Warren Harbeck

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