Skywatch Line for Friday, October 19 through Sunday, October 21, 2018

This is Dudley Observatory’s Skywatch Line for Friday, October 19 through Sunday, October 21, written by Sam Salem.

On Friday, the Sun rises at 7:14am and sets at 6:07pm; the waxing gibbous Moon sets at 1:47am and rises at 4:07pm. Neptune sits 3 degrees north of the Moon on Saturday.

Look for Jupiter, at magnitude –1.8, as early as possible in evening twilight. It hovers just 5 degrees above the southwest horizon. Saturn and Mars are also visible at the same time and much easier to appreciate. Saturn shines at magnitude 0.5 and sits some 20 degrees above the southwest horizon. Mars gleams in the south-southeast at magnitude –0.9. It climbs to the meridian a little before 9pm.

On Sunday during the predawn hours, the Orionid meteor shower reaches its peak. This year, a waxing gibbous Moon will interfere with meteor watching. The best time to look will be after moonset and before the start of morning twilight, roughly between the hours of 4am and 6am The advantage of watching the meteor shower late Friday to Saturday morning, rather than the following nights is that there is less moonlight to obstruct the show. The Moon sets roughly 4 hours before sunrise on Saturday, however, it sets only about 2 hours before sunrise on Monday. The radiant point for the Orionids is in the northern part of constellation Orion, near Orion’s club. The radiant point lies between Betelgeuse and the eastern “foot” of Gemini. The meteors appear in all parts of the sky. But if you trace the paths of the meteors backwards, you’ll see they all seem to come from the Orion constellation. The shower offers perhaps 10 to 15 meteors per hour in a dark sky. This is a modest display made up of debris shed by Comet Halley. The Orionid meteor shower is the second meteor shower created by Comet Halley. The Eta Aquarids, in May, is the other meteor shower created by debris left by the comet. Halley takes around 76 years to make a complete revolution around the Sun. It will next be visible from Earth in 2061.

Arcturus, in the constellation Bootes, the Herdsman, shines in the west to northwest after sunset. Arcturus adorns the western evening sky all through October. Arcturus is one of three stars noticeable for flashing in colors at this time of year. The arc of the Big Dipper handle extended outward always points to orange-colored Arcturus. Capella, in the constellation Auriga, the Charioteer, is the second star. It sits now in the northeast in mid-evening. Sirius, in the constellation Canis Major, the Greater Dog, is the third flashing star of the season. It sits in the south before dawn. All three stars appear to be flashing colors for the same reason. All three stars are bright and noticeably low in the sky at this time of year. Objects low in the sky are seen through a greater thickness of atmosphere than when they are overhead. The atmosphere refracts or splits the stars’ light to cause these stars to flash in the colors of the rainbow.

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