Skywatch Line for Friday, June 15 through Sunday, June 17, 2018

This is Dudley Observatory’s Skywatch Line for Friday, June 15 through Sunday, June 17, written by Sam Salem.

On Friday, the Sun rises at 5:17am and sets at 8:36pm; the waxing crescent Moon rises at 7:15am and sets at 10:31pm. On Friday at dusk look to the west to catch the very thin crescent Moon sitting below and to the right of Venus. On Saturday after sunset the crescent Moon is positioned to the left of Venus. On Sunday the Moon approaches Regulus, the brightest star in constellation Leo.

This weekend, look east for the sparkling blue-white star Vega, the brightest star in the constellation Lyra the Harp. Vega is the brightest of the Summer Triangle’s three stars. Look to the lower left of Vega for another bright star, Deneb, the brightest in the constellation Cygnus the Swan and the third brightest in the Summer Triangle. An outstretched hand at an arm length approximates the distance from Vega to Deneb. Look to the lower right of Vega to locate the Summer Triangle’s second brightest star, Altair, the brightest star in the constellation Aquila the Eagle. Under a dark sky on a moonless night, you can see the Milky Way passing in between the Summer Triangle stars Vega and Altair. Usually the term Milky Way refers to the cross-sectional view of the galactic disk, whereby innumerable stars congregate into a cloudy trail, although every star that you see with the unaided eye is a member of our Milky Way galaxy. In summer, the Summer Triangle appears in the east at nightfall, high overhead after midnight and in the west at dawn. When the stars of the Summer Triangle light up the eastern twilight dusk in middle to late June, it’s a sign of spring giving way to summer. When the Summer Triangle is seen high in the south to overhead at dusk and early evening, it’s an indication that summer has receded into fall.

The moonless sky this weekend offers an opportunity to view globular star clusters. The greatest concentration of these objects is found in constellations Sagittarius and Ophiuchus. Each of these constellations holds seven Messier globulars. The clusters located in the big, sprawling figure of Ophiuchus are easier to catch since most of them are higher in the sky than the Sagittarius clusters. Start the Ophiuchus globular hunt with the biggest and brightest of the group, M10 and M12. You can see them in binoculars, however, like most they come into their own when viewed in a telescope. Head east for the dimmer M14, then seek out M19 and M62, which lie so far south. They look as though they belong to neighboring Scorpius. The most challenging of the Ophiuchus Seven are M9 and M107. They’re fainter and smaller than the rest. You will have to push the magnification a little higher when you search for them. If you look with enough care, you’ll discover that no two are exactly alike.

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