Skywatch Line for Friday, April 10, through Sunday, April 12, written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, April 10, through Sunday, April 12, written by Sam Salem.
On Friday, Sun rises at 6:22am and sets at 7:32pm; Moon rises at 3:02am and sets at 11:54am.
Last Quarter Moon occurs early morning on Friday at 12:52am. Look for it high in the sky before dawn.
Venus, at magnitude –3.9, shines low in the western evening twilight. Try to find it about a fist at arm’s length above horizontal fifty minutes after sunset, Venus sets soon after the end of twilight.
Jupiter, magnitude –2.1, shines nearly overhead southwest at nightfall. The giant planet sits in constellation Gemini, below the bright stars Castor and Pollux, just 2.5° west of magnitude 3.5-star “Wasat”, or Delta Geminorum. Later in the evening Jupiter swings lower toward the west. It sets around 2 am, on the west-northwest horizon. In a telescope Jupiter is 39 arcseconds wide. It’s shrinking and fading as Earth pulls farther ahead of it in our faster orbit around the Sun.
“Wasat” is Arabic for “middle”, likely referring to the star’s location in the middle of Gemini. “Wasat” is a multiple star system, visible to the naked eye. It sits just south of the ecliptic in the center of Gemini. “Wasat” is noted for being near the location of Pluto when it was discovered in 1930. At that time, Pluto was in the constellation Gemini. The discovery was made by comparing photographic plates of a star-rich region near “Wasat”.
Uranus, magnitude 5.8 in constellation Taurus, sits 4° south of the Pleiades. It is still some 30° high in the west at the end of twilight. At high power in a telescope, it’s a tiny non-stellar dot, 3.5 arcseconds wide.
Look southwest for the two Dog Stars stand vertically aligned in late twilight. Sirius in constellation Canis Major sits below, and Procyon in constellation Canis Minor is high above. Look to the right of their midpoint for orange Betelgeuse, the third star of the equilateral Winter Triangle. It marks Orion’s shoulder.
Look upper left of Procyon, by about a fist and a half at arm’s length, for the dim head of Hydra, the enormous Sea Serpent. The head is a group of 3rd. and 4th. magnitude stars about the size of your thumb at arm’s length. About a fist and a half lower left of Hydra’s head shines Alphard, his 2nd-magnitude orange heart. The rest of Hydra zigzags faintly from Alphard all the way down to the southeast horizon. Hydra’s head makes a roughly equilateral triangle with Regulus and Alphard. Hydra is the largest and longest of the 88 constellations, stretching over 100 degrees across the southern sky, representing a mythical sea serpent. Its brightest orange giant star “Alphard” is situated in a dim region of the sky. Its name, derived from Arabic, means “the solitary one”. It’s often associated with the arrival of Spring.