This is Dudley Observatory’s Skywatch Line for Friday, April 13 through Sunday, April 15, written by Sam Salem.
On Friday, the Sun rises at 6:17am and sets at 7:36pm; the waning crescent Moon rises at 5:24am and sets at 5:03pm. New Moon occurs on Sunday at 9:57pm.
The winter constellations are crowded into the west during early evening. Venus gleams at magnitude –3.9 and sits roughly 10 degrees above the horizon one hour after sunset. Jupiter, at magnitude –2.4, clears the east-southeast horizon after 10:00pm. Wait a few hours for the planet to gain some elevation before you turn your scope on it. Jupiter reaches the meridian around 3:15am. Saturn is up shortly after 2:00am and Mars joins it some 20 minutes later. The space between the two planets is starting to grow after they have been keeping each other company for the past several weeks. Both planets are located in constellation Sagittarius and are closely matched in brightness. Saturn gleams at magnitude 0.4, while Mars is a little brighter at magnitude 0.1.
This weekend head over to constellation Cancer, the Crab, the faintest constellation of the Zodiac. Cancer, the Crab, lies between the two brightest starts of Gemini, Castor and Pollux, and Leo’s brightest star Regulus. Try to locate the open cluster M44, also known as the Beehive Cluster in Cancer. M44 is a fine binocular object that’s easy to locate. The one-degree-wide clump of stars is parked midway and a little west of a line joining Delta and Gamma Cancri. At magnitude 3.9, Delta is Cancer’s brightest star. Another delightful open cluster is M67. Nicknamed the King Cobra Cluster, M67 is an open cluster located in the constellation Cancer. It can be found roughly halfway and slightly above the imaginary line connecting the bright stars Regulus in constellation Leo and Procyon in constellation Canis Minor. Under a dark sky the little stellar gathering is visible in steadily held binoculars as a fuzzy patch. M67 is one of the oldest known open clusters and the single oldest open cluster listed by Messier in his catalogue. The estimated age of M67 is in the range from 3.2 to 5 billion years. Open clusters are typically younger and the stars tend to disperse over time, usually before they reach this age. For example, the Beehive Cluster M44 is only 600 million years old.
Constellation Cancer is also home to a number of fine double stars, including Iota Cancri. Iota is a striking sight in small telescopes. It features a 4.1-magnitude yellow star contrasting with a 6.0-magnitude blue companion, separated by a generous 31 arc seconds. The two are easily split in any scope used at low power. The double star is located 7 degrees north of the M44, Beehive Cluster.
Saturday marks the 389th. birthday of the Dutch physicist and astronomer Christiaan Huygens who founded the wave theory of light, discovered the true shape of the rings of Saturn, and contributed to the study of the action of forces on bodies., In 1655, Huygens discovered the first moon of Saturn, later named Titan, using a lens he ground for himself. In 1656, he patented the first pendulum clock, which he developed to enable exact time measurement while observing the heavens. Cristiaan Huygens developed theories on centrifugal force in circular motion, which influenced Sir Isaac Newton in formulating his Law of Gravity. Huygens also studied and drew the first maps of Mars. On January 14, 2005, a NASA space probe, named after Huygens, landed on Titan.