Skywatch Line for Monday July 26th and Tuesday July 27th, 2021

This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday July 26th, and 27th, written by Joe Slomka.

The Sun sets at 8:22 PM; night falls at 10:22. Dawn begins at 3:42 AM and ends with the Sun rising at 5:42.

Monday, the Moon, in Aquarius, appears about 31 arc-minutes in size and appears 90% illuminated; it sets at 10:24 PM. Tuesday, it moves into Cetus, rising at 9:27 AM, slightly thinner and sets at 10:48 PM.

Venus and Mars, in Leo, are still visible, but low in the West. First magnitude Mars sets at 9:28 PM, but only 5° above the horizon. Venus, blazing with minus 3rd magnitude, 12 arc-seconds in size, appears about 7 arc-seconds above and to Mars’ upper left. Venus sets at 9:48 PM. Both may require an unobstructed view and binoculars or telescope.

While Mars and Jupiter are setting, Saturn, in Capricornus, rises in the East at 8:39, shines with zero magnitude and is a moderate 18 arc-seconds. Jupiter, in Aquarius, rises at 9:33 PM and appears large with 48 arc-seconds. By 11 PM, both join the Moon and are high enough for details. Saturn is a favorite for first time observers. The ring system never fails to amaze. Telescopic sky watchers can see the Great Red Spot, a giant storm on Jupiter, at 3:23 AM on Tuesday and witness the Jovian Moon Io’s march across the face of Jupiter from 9:37 PM until 12:29 AM on Wednesday.

Neptune shares Aquarius with Jupiter, rising at 10:25 PM, 7th magnitude and a small 2 arc-seconds; by Midnight it is 16° high and 6° above the Moon. Uranus is last, in Aries, rising at 12:26 AM, fifth magnitude, 4 arc-seconds and 17° high at 2 AM.

The Southern Delta Aquariid Meteor Shower peaks on July 29th, but actually happens all week. However, the brilliant Moon will wash out most meteors; only the brightest will be visible.

As night falls, Scorpius lies due South and obvious to even the casual sky watcher. Scorpius is one of the oldest constellations; its origins lie in the sands of Babylon. Star names betray its history. Sumerians and Babylonians gave us the Zodiac as we know it, and named them in their languages. When the Greeks occupied the Middle East, they imposed their own names – as did the later Romans. Conquering Arabs also renamed the constellations and stars. Crusaders, who came across Arabic scientific documents, republished all this knowledge, forgotten during the Dark Ages.

Antares is the common name for the red star that marks the Scorpion’s heart. The word Antares means “rival of Ares,” the Greek word for the Roman god – Mars. Indeed, the two do look alike. Of course, Antares is a giant star, while Mars is a small planet. The two stars on either side of Antares were called “Al Niyat,” Arabic for “the Arteries.” Beta, Delta and Nu, in the head, were called Graffias, Dschubba and Jabbah. The stinger’s stars are Shaula and Lesath – again Arabic names. Theta, the star that bends upward to form the tail is called by two Sumerian names: Girtab and Sargas.

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