Skywatch Line for Friday, May 24 through Sunday, May 26, 2019

This is Dudley Observatory’s Skywatch Line for Friday, May 24 through Sunday, May 26, written by Sam Salem.

On Friday, Sun rises at 5:25am and sets at 8:21pm; the waning gibbous Moon rises at 12:44am and sets at 10:24am. The last-quarter Moon occurs at 12:33pm on Sunday. This Sunday marks the year’s closest coincidence of last quarter Moon with lunar apogee, the Moon’s farthest point from Earth in its monthly orbit.

The evening sky features two planets, one nearing the end of its run, the other entering its prime. Mars shines at magnitude 1.7 low in the west-northwest at dusk. As Mars sinks into the horizon haze, Jupiter rises in the southeast. Jupiter, gleaming at magnitude –2.6, is a telescopic sight later in the night when it gains altitude. Jupiter is at its highest around 2am. Rising shortly before midnight is Saturn. At magnitude 0.3, Saturn is easy to pick out from the rather dim stars of eastern Sagittarius. Saturn is at its best around 4:15am, as morning twilight begins to noticeably brighten the sky. Venus, at magnitude –3.8, is the last planet to appear. It comes up less than an hour before daybreak. The “morning star” should be easy find if you have an unobstructed horizon.

Let the bright star Vega, in the constellation Lyra, the Harp, guide you to a famous star pattern in Hercules called the Keystone and then to the Great Cluster in Hercules, aka M13. You can easily find the brilliant star Vega in the eastern sky at dusk and nightfall. Look for the Keystone asterism to the upper right of the brilliant blue-white star Vega. You can also locate the Keystone by using Vega in conjunction with the brilliant yellow-orange star Arcturus, in the constellation Bootes, the Herdsman. Arcturus shines quite high in the southeast sky at nightfall and evening. The only star-like object to outshine these stars is planet Jupiter, rather low in the southwest sky at nightfall. The Keystone is found about one-third the way from Vega to Arcturus. Locate the four modestly bright stars forming the Keystone of Hercules. On the Arcturus side of the Keystone, M13 is found between the stars Eta Herculis and Zeta Herculis. Through binoculars, this cluster looks like a dim and somewhat hazy star. But the telescope begins to resolve this faint fuzzy into what it really is a great big, globe-shaped stellar city populated with hundreds of thousands of stars. The Keystone and the Hercules cluster swing high overhead after midnight, and are found in the western sky before dawn.

Under dark sky, Corona Borealis, aka the Northern Crown, is easy to find. It’s an almost-perfect semi-circle of stars. You’ll find this beautiful pattern in the evening sky from now until October. The constellation Corona Borealis is located more or less along a line between two bright stars, Arcturus and Vega, . At nightfall and early evening, you’ll see Arcturus fairly high in the east to northeast, noticeable for its brightness and yellow-orange color. Vega will be rather low in northeast – bright and blue-white in color. The Northern Crown is more or less between these two bright stars. It’s a semi-circle of stars, very noticeable in a dark sky.

Sunday marks the 193th. birthday of the English Astronomer Richard Christopher Carrington. Carrington discovered the equatorial acceleration of the Sun by observing the motion of sunspots. He discovered that the Sun rotates faster at the equator than near the poles. He also discovered the movement of sunspot zones toward the Sun’s equator as the solar cycle progresses. Carrington devoted himself to the study of sunspots and his work, extending from 1853 to 1861, was collected in Observation of the Spots of the Sun (1863). Carrington also was the first to observe a Sun flare in 1859. He was observing a prominent group of sunspots when suddenly two patches of intensely bright and white light broke out, which brightened rapidly and decayed. The flare he had seen was of the rare variety that is visible in white light.

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