Skywatch Line for Monday July 5th and Tuesday July 6th, 2021

This is the Dudley Observatory’s Skywatch Line for Monday (Independence Day) and Tuesday July 5th, and 6th written by Joe Slomka.
The Sun sets at 8:37 PM; night falls at 10:50. Dawn begins at 3:11 AM and ends with the Sun rising at 5:24.

Monday finds the Earth furthest from the Sun, 152,100,527 KM (94,510,885 miles)- 3.4% more distant than in northern hemisphere Winter.
Taurus hosts the Moon on both nights. The 25-day-old Moon sets at 4:54 PM on Monday, rises at 2:42 AM on Tuesday, sets at 5:56 PM and rises at 3:15 AM on Wednesday.

Mars and Venus, in Cancer, continue to be visible low in the West. Venus blazes at minus 3rd magnitude and is a moderate 11 arc-seconds in our binoculars and telescopes. Mars shines with 1st magnitude and small 3 arc-seconds small. Both are very low and require an unobstructed view. Both set by 10:17 PM. Note that Venus climbs higher nightly while Mars becomes lower nightly.

Soon bright planets follow. Saturn, in Capricornus rises at 10:06 PM, shines with zero magnitude and presents a moderate size of 18 arc-seconds; it is highest at 2:59 AM. Jupiter, in Aquarius, trails by rising at 10:59 PM and is highest at 4:17 AM. Telescopic observers can witness the moon Ganymede be eclipsed at 12:41 AM on Wednesday and the Great Red Spot at 1:07 AM. Jupiter begins retrograde motion, which means it appears to halt and then back up in the sky.

Neptune, also in Aquarius, arises at 10:48 PM, shining with 7th magnitude and a tiny 2 arc-seconds; it’s 13° high by 1 AM. In Aries, Uranus joins the scene by rising at 1:47 AM, glimmers with 5th magnitude and a larger 3 arc-seconds; it is 13° high by 2 AM. By 3 AM, Saturn, Jupiter, Neptune, Uranus and the Moon form a brilliant chain in the eastern sky. Mercury is the challenge object. In Taurus, it rises at 4:07 AM, shines with zero magnitude and is, for Mercury, a large 7 arc-seconds. It is 4° high in the East. Mercury reached its greatest separation from the Sun on Sunday; its small size, low position and the rapidly brightening dawn makes observing difficult. As a possible aid to the observer, the Moon appears between Mercury and the star Aldebaran in Taurus’ horns, during Wednesday’s dawn.

The Fourth of July is famous for fireworks. In the year 1054 Nature staged her own fireworks show. Chinese astronomers saw a new star in Taurus. Accounts said it “shone like a comet.” The “guest star” shone in daylight for 23 days and was visible nightly for a year and a half. Most textbooks remark that no one in Europe or the Mideast saw it. However, North American natives saw it and made rock carvings depicting it. Charles Messier made it the first in his list of false comet objects. We now know the Crab Nebula is the remnant of a star that blew up. It blazed with the brightness of 500 million suns and produced a pulsar, a residue body that spins rapidly and emits regular radio pulses.

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