Skywatch Line for Friday, July 9, through Sunday, July 11, 2021

This is Dudley Observatory’s Skywatch Line for Friday, July 9, through Sunday, July 11, written by Sam Salem.

On Friday, Sun rises at 5:26am and sets at 8:35pm; Moon rises at 4:43am and sets at 8:45pm. The Moon will reach its new phase on Friday at 9:17 pm.

Low in the west-northwestern sky after sunset on Sunday, the young crescent Moon will shine a generous palm’s width to the right of bright Venus, and much fainter Mars. On the following evening, the Moon’s orbital motion will lift it to sit a similar distance above those two planets. Venus, at magnitude –3.8, shines low in the west-northwest during twilight. Tiny Mars, nearly 200 times fainter at magnitude +1.8, is closing in on Venus from the upper left. They’re separated by 2 degrees on Friday. They’ll be in conjunction, ½° apart, on Monday and Tuesday. Both planets set before twilight ends.

Saturn, in constellation Capricornus, and brighter Jupiter, in constellation Aquarius, show up by late evening. Saturn, at magnitude +0.4, rises around the end of twilight. Jupiter, at magnitude –2.6, comes up one hour later, to Saturn’s lower left. They’re up in fine view after midnight, and they’re highest in the south at their telescopic best in the hour before dawn begins.

You can see constellation of Ophiuchus, the Serpent Bearer on these July nights. You will need a dark sky to be able to see its faint stars. Look for Ophiuchus in the direction south at nightfall. Use bright red star Antares in the constellation Scorpius the Scorpion to help you find Ophiuchus. Look for Ophiuchus a short hop to the north of Antares. Ophiuchus’ brightest star, the 2nd-magnitude star called Rasalhague, highlights the head of Ophiuchus. Rasalhague is nowhere near as bright as Antares. Rasalhague is a binary star. Its name is derived from an Arabic word that means “the head of the serpent collector”. Ophiuchus the Serpent Bearer is sometimes called the 13th or forgotten constellation of the zodiac. The Sun passes in front of Ophiuchus from about November 30 to December 18 each year.

If you have a dark enough sky on these moonless nights, the Milky Way now forms a magnificent arch high across the whole eastern sky. It runs all the way from below Cassiopeia in the north-northeast, up and across Cygnus and the Summer Triangle in the east, and down past the spout of the Sagittarius Teapot in the south.

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