Skywatch Line for Friday, July 2, through Sunday, July 4, 2021

This is Dudley Observatory’s Skywatch Line for Friday, July 2, through Sunday, July 4, written by Sam Salem.

On Friday, Sun rises at 5:22am and sets at 8:37pm; Moon rises at 1:07am and sets at 1:50pm. When the waning crescent Moon rises around 2:00am in the east on Sunday, it will be positioned a slim palm’s width to the right of the magnitude 5.8 planet Uranus, close enough for them to share the view in binoculars. Try to find the planet before 4:30am before the brightening dawn sky overwhelm it.

Mercury will be visible in the pre-dawn sky during much of July. On Sunday, Mercury will reach a maximum angle of 22 degrees west of the Sun and peak visibility for its morning apparition. The best time to see the planet will come just before 5:00am, when Mercury will sit very low in the east-northeastern sky. In a telescope the planet will show a 36-per-cent-illuminated waxing crescent phase. Mercury’s position well below the morning ecliptic will make this apparition a poor one for Northern Hemisphere observers.

On Friday, Venus shines low in the west-northwest during twilight, with vastly fainter Mars now just 6 degrees to its upper left. They set before twilight’s end.
Venus hardly moves now with respect to your landscape from week to week, but its background stars are sliding toward the lower right. On Friday, the Beehive Cluster, M44, passes behind Venus. This will be difficult to observe. You’ll have to catch the narrow time window between the sky being too bright and Venus and the Beehive getting too low and setting. Try binoculars or a wide-field scope.

Jupiter, at magnitude -2.6, and Saturn, at magnitude +0.4, rise in late evening. They shine at their highest and telescopic best in the south before dawn. Saturn sits 20 degrees to Jupiter’s right. Before dawn, look 20 degrees below or lower left Jupiter for Fomalhaut. It forms an isosceles right triangle with Jupiter and Saturn. Jupiter is at the almost right angle.

On July evenings, look eastward for the season’s signature star formation, the Summer Triangle asterism. Its stars are the first three to light up the eastern half of the sky after sunset. Their bright and sparkling radiance is visible even from light-polluted cities or on a moonlit night. Its top star is Vega, the brightest in all the east. The brightest to Vega’s lower left is Deneb. Farther to Vega’s lower right is Altair. The Milky Way runs a little inside the Triangle’s lower edge. As evening grows later and even Altair rises high, look left of Altair, by hardly more than a fist, for the compact little constellation Delphinus, the Dolphin. Then try for even fainter, smaller Sagitta, the Arrow, to Altair’s upper left and just a little closer. The Arrow aims lower left, past the nose of Delphinus.

On July 4th. 1054, a supernova, a violently exploding star, was seen in China and in other places in the world. The supernova was visible in daylight for 23 days and at night for almost 2 years. References to the event were found in a later Japanese and Arabic documents. Rock paintings in North America suggest that Native Indians in Arizona and New Mexico saw it. It is believed the Crab Nebula in the constellation Taurus is the remanent of this supernova. The core of the exploded star formed the Crab Pulsar.

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