A P R I L   2 0 0 2   S K Y W A T C H

by Maya del Mar

April is a stunning month in the sky—we have two show stoppers!

A new comet appears.

First is that rare event, a visible comet. I haven’t seen Comet Ikeya-Zhang yet, but I read in the San Francisco Chronicle of March 21 that it can be seen after twilight low in the western sky, with its tail rising straight up. My western horizon is obscured by high hills, but on a clear night I’ll check the view from the ferry.

The comet is said to appear below and to the right of reddish Mars.

All five visible planets can be seen at once!

That puts it right in line with our second show-stopper: a fine vista of all five of the visible planets as they slowly set behind the evening horizon. It’s not often that all five are visible at once, particularly in such a close grouping.

Venus has become an evening star again, and April opens with that bright jewel close to the western horizon a half hour after sunset. Reddish Mars, now faint, is a little above Venus and a bit to its left. Look below Mars and to its right for the comet. Sometimes a comet is visible only as a faintly fuzzy spot. Find some binoculars to check that area out.

Saturn is a little above Mars, just above the orange star Aldebaran. Saturn is the brighter one of the pair. Venus is catching up to Mars, Mars is catching up to Saturn, and by the end of the month Mercury will appear just below Venus. As the month ends, these four planets will be separated by only 13 degrees.

Mercury is always elusive. Just to see it is a trophy treat. It hangs out close to Sun, and will sink below the horizon two hours after sunset on April 30.

And then there’s Jupiter, King of the tribe, sitting up there high and bright and mighty, gracing the evening skies with his brilliance—perhaps 60 degrees above the horizon. As you gaze at Jupiter, you might realize that Chiron lies opposite Jupiter in the heavens. This means that twelve hours later, in the morning, Chiron will be traversing the western sky.

Watch the planets move.

It’s fun to track the movement of the fast-moving planets—Mercury, Venus, and Mars. If you watch them every night, you can watch the "catching-up" process, and see how they change in relation to the stars. The part of the sky which they’re traversing—specifically the constellation of Taurus—happens to have many bright stars, so this is an extra dividend.

Sometimes it’s hard to differentiate planets from bright stars. If you watch every night, you’ll soon notice which ones change position. ("Planet" means "wanderer.") Another way to track is with the moon. After all, sun, moon, and planets all follow the same apparent pathway—the ecliptic.

On April 14, the delicate new crescent moon reaches Venus. On April 15, Moon is close to Mars, and on April 16, it reaches Saturn. On April 18 it reaches Jupiter. I wrote about the busy month of April. You can see here in the sky what a busy start this lunar month is undertaking.

See Mercury now.

Mercury is now in its best evening apparation of the year, but even so, it’s visible for only three weeks, and then only shortly after sunset. In the last week of April, start looking about 40 minutes after sunset, and spot brilliant Venus as a guide. Mercury is halfway from the horizon to Venus.

A meteor shower adds to the sky bounty.

And if these marvelous sky spectacles aren’t enough, in the early morning hours of April 22, we can see the Lyrid meteor shower. These meteors appear to radiate from the constellation Lyra the Harp. We can track Lyra through the night sky because its bright blue star Vega rises in the northeast shortly after sunset. By 4 a.m. Vega has moved directly overhead in the San Francisco area. About 10-15 meteors/hour are expected.

It’s a very special treat to have such an exciting and photogenic night sky as we do this April. Take advantage of it!