This is the Skywatch Line for Monday and Tuesday, June 3rd and 4th, written by Joe Slomka.
The Sun sets at 8:28 PM; night falls at 10:40. Dawn begins at 3:06 AM and ends with the Sun rising at 5:18.
Mars is no longer the only planet in the evening sky. The Red Planet, Mercury and the stars of Gemini all appear together this month. Mars appears about 98% illuminated, shines with 2nd magnitude, but is only 15º high in the West. Mercury makes a temporary visit to the evening sky by occupying Taurus, appearing 80% lit, but glowing with minus zero magnitude. While Mars becomes more difficult daily, Mercury, 12º below Mars, actually gets better for the first half of June. Mercury sets at 9:48 PM, Mars at 10:41 PM.
The Moon turns “New” on Monday, which means we do not see it. Tuesday’s 2-day-old Moon occupies Gemini, appearing a slim 3% lit, 7º high and 6º to Mercury’s lower left. The Moon sets at 9:54 PM.
Jupiter rises in the eastern constellation of Ophiuchus at 8:51 PM. It blazes with minus 2nd magnitude and appears 45 arc-seconds in size. By twilight’s end, it is higher at 14º. The controversial Great Red Spot can be telescopically observed at 2:22 AM, Wednesday morning. Tuesday finds the moon Ganymede’s shadow ending its crossing of Jupiter’s face at 9:55 PM, but Ganymede begins its crossing at 10:23 PM. A few minutes later, the moon Io ends its shadow crossing at 10:42 and Io’s crossing at 10:49. Such Double Shadow Transits are quite rare and always a treat for visual telescopic astronomers.
Dwarf Planet 1Ceres shares Ophiuchus with Jupiter. It glows with 7th magnitude but exhibits a tiny 0.7 arc-seconds in size. It rises and joins Jupiter in an all-night excursion, beginning at 7:43 PM and is best observed at 12:33 AM. Finder charts are available from various astronomy websites.
Saturn, 29º to Jupiter’s lower left, rises in Sagittarius at 10:53 PM. It shines with zero magnitude and appears about a third of Jupiter’s size near Sagittarius’ Teapot. It is brightening in preparation for its July Opposition. Saturn is best seen at 3:30 AM.
Neptune rises, at 1:42 AM, in Aquarius, glowing with 8th magnitude and appearing 2 arc-seconds in size, but 14º high. By Sunrise, it is about 29º high. Again, finder charts assist the early bird star gazer.
Uranus rises in Aries at 3:25 AM, shining with 6th magnitude, 3 arc-seconds in size and 13º high. Venus, rising in Taurus at 4:22 AM blazes with minus 4th magnitude, appearing about 95% lit, 10 arc-seconds in size and a meager 3º high. Both planets are difficult to find in the rapidly brightening Dawn sky and pose a challenge.
Thursday is the 75th anniversary of the Normandy Invasion that eventually ended the European Theater of WWII. General Eisenhower, overall commander, required a set of astronomical conditions for the invasion: lunar phase, tides and sunrise. The Moon on the night of June 5/6 was 99% lit, but only 23º high. This enabled airborne troops to land and attack. It also enabled battleships and cruisers to locate and bombard German shore positions before assault troops hit the beaches. More importantly were tidal considerations. Twice a day the Normandy tides rose 19 feet from low to high. Low tide was at 5:23 AM; shelling began at 5:50 and the Sun rose at 5:59. The first wave arrived at 6:30. Low tide was preferred because the enemy seeded the shoreline with obstacles and explosives. After the first wave landed, explosive demolition teams were to clear these obstacles, however rapidly rising water made their efforts difficult. The ocean was rising at a rate of one foot per 10 minutes. Many traps went undamaged. In addition, landing craft had to evade other hazards: piles driven into the shore with mines that would explode if a landing craft hit it. Despite hazards and fierce opposition, the allied forces made progress and drove the enemy from the beaches to make a slender toe-hold on the French coast.