This is Dudley Observatory’s Skywatch Line for Friday, June 14 through Sunday, June 16, written by Sam Salem.
On Friday, Sun rises at 5:17am and sets at 8:36pm; the waxing gibbous Moon rises at 5:51pm and sets at 3:38am. On Saturday night, the bright Moon forms a triangle with Jupiter, to its lower left, and Antares, to its lower right. On Sunday evening, the nearly full Moon and Jupiter rise together side-by-side in the southeast at sunset. The two objects will be a little more than four degrees apart, offering a fine naked-eye sight early in the evening. Full Moon occurs on Monday at 4:31am.
Three planets emerge as evening twilight begins to fade. Mercury, in constellation Gemini, lies low in the west-northwest and gradually approaching Mars. On Sunday evening, Mercury lies 1 degree lower right of Mars. Use binoculars to watch the gap between the two planets noticeably shrink from night to night. This week Mercury fades by almost half, from magnitude –0.6 to –0.1. However, Mercury is much brighter than magnitude 1.8 Mars. Don’t confuse Mercury with Procyon, some 25 degrees to its left, or Capella, about the same distance to its right. Jupiter, gleaming at magnitude –2.6, rises in the southeast a little before sunset and culminates roughly around 12:30am. Saturn, at magnitude 0.2, rises a little before 10:30pm. It reaches the meridian around 2:30am. Venus, at magnitude –3.8, is very slowly losing altitude as its current apparition winds down. Venus clears the east-northeast horizon less than one hour before sunrise.
Jupiter and Saturn’s moons are good telescopic targets this moonlit weekend. Jupiter is at its brightest and closest to the Earth for the year. Swing your telescope to the giant planet’s way. Though it rises around sunset, it still takes time to climb high enough for a good view. Come the end of the month, Jupiter stands 20 degrees high before twilight ends. Try to observe Jupiter every clear night, the better to catch nights of calm and steady seeing when the planet sits rock-steady and sharp. When the air calms and seeing conditions allow, you can make out the prominent North and South Equatorial Belts. Jupiter’s iconic Great Red Spot (GRS) has been shrinking over the past several decades and currently spans about 1.3 Earths. But it remains colorful and easy to see at 100 times magnification and higher in good seeing conditions.
The moons of Saturn are all fainter than Jupiter’s moons but some are within range of small to moderate-sized telescopes. Titan shines gamely at magnitude 8.4, and is usually the brightest point of light near Saturn. With an 8-inch scope, you might see as many as four additional satellites, including Rhea (magnitude 9.7), Tethys (10.3), Dione (10.4) and, under the right conditions, Enceladus (11.8). At last count, Saturn has 62 satellites ranging in size from 5,149, Titan, down to jagged moonlets smaller than Mount Everest.