This is the Dudley Observatory Skywatch Line for Monday and Tuesday, December seventh and eighth written by Joe Slomka.
The Sun sets at 4:21 PM; night falls at 6:03. Dawn breaks at 5:31 and ends with the Sun rising at 7:13.
The early evening sky holds no bright planets. Nightfall reveals Neptune, Uranus and the asteroid 4Vesta. Neptune still resides in Aquarius; it sets at 8:52 PM. Pisces still contains Uranus, which is best observed at 7:52 PM. Both gas giants appear blue-green; they require detailed star charts from astronomy magazines, websites and apps. Asteroid 4Vesta hangs out about one-and-a-half degrees from the star Iota, in Cetus. Tiny Vesta also requires a detailed star chart and is best detected at 7:02 PM.
We have been following the continuing planetary parade for the past few months. Bright Jupiter rises first a bit before Midnight. By Astronomical Dawn, it is quite high in Leo, by the lion’s rear leg. On Tuesday morning, the Jovian moon Europa disappears into Jupiter’s shadow at 3:36 AM; at 4:17 AM also Tuesday, the moon Callisto’s shadow begins to march across the planet’s face.
Dawn finds Mars, in Virgo, about 23 degrees below Jupiter; Mars rose about 2 AM. Mars shines at 1.5 magnitude, much dimmer than Jupiter; but, its distinctive rust color gives it away. It appears between Virgo’s bright stars Porrima and Spica. A telescope shows Mars to be about 93 percent illuminated.
Blazing Venus rises, also in Virgo, at 3:34 AM near the star Kappa. It is easily identified about eighteen-and-a-half degrees below Mars. Under moderate powers, Venus appears about ninety percent illuminated.
Venus serves as a guide to Comet Catalina. Catalina shines at magnitude 4.8. It is about five degrees east of Venus. Both may fit within a wide view telescope or binoculars. As previously mentioned, Catalina is slowly climbing higher daily.
The twenty-seven-day-old Moon shines about eight degrees below Venus. In Libra, it shines at magnitude minus 4.9, but is only 8.5 percent illuminated. Wednesday finds it lower in Libra and only minus 2.5 magnitude and four percent illuminated.
Every history student knows that December 7th marks the anniversary of the Japanese attack on Pearl Harbor. Few people are aware of the date’s astronomical significance. The Japanese high command chose that date because the eighteen-day-old Moon rose before midnight and shone at 87 percent, permitting attack planes to launch and fly to their targets. However, the Moon almost helped foil the surprise raid. The Condor, an American minesweeper, spotted a submarine periscope silhouetted against the moonlight. The Condor called the Ward, a destroyer, who attacked a second submarine and radioed the incident to headquarters. That report was not heeded. Had that information been acted upon, the American fleet would have had at least an hour and a half to prepare.