Touring the April Sky

As the celestial sphere turns westward through the seasons, old constellations sink into the sunset and new ones rise in the east. The rule to remember is this: looking two hours later at night is like looking one month later in the year. Planets can be the exception. Venus, for instance, has been getting higher in the west each month, not lower. Now Venus blazes aloft in western twilight like nothing else in the sky.

During April, Venus has some interesting celestial encounters. It passes lower left of the delicate little Pleiades star cluster on the 10th to 12th. The waxing crescent Moon hangs with Venus on the April 19th just when Venus is passing upper right of Aldebaran, the brightest star in Taurus. At month's end, Venus reaches the star Elnath, which links Taurus to neighboring Auriga.

Saturn is the other planet of April evenings. Look for it shining very high up toward the south after the sky darkens. Left of it is the Sickle star pattern of Leo, with Regulus forming the bottom of the Sickle's handle. To its immediate right is the dim constellation of Cancer, the Crab. Cancer's showpiece object is the loose star cluster called the Beehive, located the width of a fist at arm's length to Saturn's right. In a dark sky the Beehive Cluster looks like a soft glow, but binoculars will reveal dozens of individual stars.

Rather far below Saturn and Regulus is Alphard, "the Lonely One," forming the fiery orange heart of Hydra, the sky's enormously long Sea Serpent. Look for Hydra's distinctive head halfway from Alphard to Procyon and a little above.

Nearly at its highest in the north now is the Big Dipper, almost overhead. According to old farmer's lore, it's upside down as if dumping April showers. The showers must take quite a while to reach Earth, since whenever you see the Dipper the sky is obviously clear!

The two Pointer stars of the Big Dipper, forming the left end of its bowl, point down nearly to Polaris, the North Star. It's below them by three fist-widths. Polaris marks the handle-end of the notoriously dim Little Dipper, which on spring evenings extends to Polaris's right.

Way down below Polaris is dim King Cepheus, hard to see. Much easier is his bright wife Queen Cassiopeia to his left. The W-shaped pattern of Cassiopeia's five brightest stars is sometimes called her chair or throne (complete with a footrest), but to me it looks awfully uncomfortable.

The brightest star on the eastern side of the sky is Arcturus, sometimes called the Spring Star for its grand arrival into good evening view at this season. Arcturus is the leading light of Böotes, the Herdsman, but you can think of this constellation as Böotes the Boot if you prefer. To me, Böotes has the shape of a low boot or slipper with Arcturus marking its long, pointy toe.

As night grows late and Arcturus climbs very high, a new spectacle arrives onstage. Bright Jupiter rises in the east-southeast around midnight or 1 a.m. at the beginning of April and 10 or 11 p.m. by month's end (depending on where you live). Give it another couple hours to ascend into good view in the southeast. By dawn Jupiter dominates the south.

© 2007 Reprinted with permission from Sky Publishing Corp.