This is the Skywatch Line for Monday and Tuesday, April 29th and 30th.
The Sun sets at 7:53 PM; night falls at 9:43. Dawn begins at 4:03 AM and ends with the Sun rising at 5:51.
Mars ends the month as the only planet visible in the evening sky. The Red Planet rises in Taurus appearing about 96% illuminated, a small 4 arc-seconds in size and shining with first magnitude. It sets at 11:20 PM.
Gas giant planet Jupiter rises in Ophiuchus just as Mars is setting. Jupiter sparkles with minus 2nd magnitude and appears a large 43 arc-seconds. By Midnight, it is about 5º high in the East and is best observed at 3:56 AM. The planet is now high enough for amateurs to study its cycles. The Great Red Spot, a giant storm, crosses Jupiter’s face at 2:43 AM on Tuesday. Also, on Tuesday, the moon Ganymede’s shadow leaves the planet’s face at 1:58 AM. At 3:43 AM, Ganymede itself begins its trek across Jupiter and ends it at 5:33 AM.
Saturn, the other gas giant planet, rises in Sagittarius at 1:18 AM. It glimmers with zero magnitude and appears about half Jupiter’s size. By Astronomical Dawn, it is about 20º high in the southeast. Saturn is stationary on Tuesday, which means that is halted its eastern movement and will shortly begin to travel westward for a while, before resuming its original path. The planet is not really reversing direction. This is an illusion caused by the differing orbital speeds of Earth and Saturn, similar to that of approaching and passing a slower car on the highway.
Neptune rises in Aquarius at 3:58 AM. It smolders with 8th magnitude and appears a tiny 2 arc-seconds in size. By Civil Dawn it is about 14º high in the East.
The waning Moon rises in Aquarius at 4:16 AM, Tuesday and at 4:41 AM on Wednesday. Tuesday the Moon appears about 20% lit, dazzles with minus 7th magnitude and appears about 30 arc-minutes in size. By Civil Dawn, is lies about 4º below Neptune and 10º high over the eastern horizon. Wednesday finds the Moon in Pisces, a bit thinner and dimmer but about as large, but about 6º above the horizon.
Venus rises in Pisces at 4:54 AM, appearing about 88% lit, blazing with minus 4th magnitude and low on the eastern horizon.
As night falls, the unmistakable shape of Leo, the Lion, dominates the evening sky. Leo is one of those constellations that look like its namesake. If one looks past Denebola, the Lion’s Tail, an observer sees a faint hazy cloud. Binoculars show it to be a galactic star cluster. This cluster is called Coma Berenices.
Unlike most constellations, Berenice was not a mythical figure. She was married to Ptolemy III of Egypt. When her brother-in-law involved the Pharaoh in a war, Berenice, like all wives, worried about her husband in battle. She vowed to Aphrodite that she would donate a lock of her hair if Ptolemy arrived home safely. He did; and she fulfilled her promise. One night the royal couple inquired of the court priest-astrologer what happened to her donation. He replied by pointing to a hazy cloud in the sky and said the gods accepted her sacrifice. Berenice is famous for another reason; she is Cleopatra’s grandmother. The modern Libyan city of Benghazi bears a modified version of her name.