In the Sky This Month

Orion is quite low in the west as night begins to fall. Its three-star belt lines up parallel to the horizon, with the hunter’s second-brightest star, orange Betelgeuse, above the belt.

The Eta Aquariid meteor shower should be at its best over the next couple of nights. It fires up as Earth flies through the orbital path of Comet Halley. Dust grains from the comet plunge into the atmosphere and vaporize, forming meteors.

The giants of the solar system form a wide triangle with the Moon early tomorrow. Jupiter, the largest planet, looks like a brilliant star to the left of the Moon. And fainter Saturn, the second-largest planet, is to the upper right of the Moon.

The planet Saturn stands to the upper left of the Moon at first light tomorrow. It looks like a bright golden star. The much brighter planet Jupiter is off to the left.

Monoceros, the unicorn, is in the west and southwest at nightfall, to the upper left of Orion’s Belt. It contains a binary star system that erupts every couple of decades. It could explode as a nova before the end of the century.

One of the smallest, faintest galaxies yet seen is a companion of our home galaxy, the Milky Way. The galaxy hasn’t changed much since it was born, when the universe was young. Segue 1 is in Leo, the lion, which springs high across the south on April nights.

Alphecca, the brightest star of Corona Borealis, the northern crown, is in the east-northeast at nightfall and climbs the eastern sky later on. Alphecca consists of two stars. One is similar to the Sun, while the other is much larger and brighter than the Sun.

The bright orange star Antares, the leading light of Scorpius, perches close to the lower right of the Moon as they climb into good view by midnight, and directly below the Moon at first light.

IC 1101 is the king of the mega-merger. The largest galaxy yet seen grew to such enormous proportions by merging with other galaxies, large and small. It is low in the east in early evening, well below the bright yellow-orange star Arcturus.

The Moon is full tonight at 10:32 p.m. CDT as it lines up opposite the Sun in our sky. Sunlight illuminates the entire lunar disk. The full Moon of April is known as the Egg Moon or Grass Moon.