Skywatch Line for Monday and Tuesday July 10th, and 11th, 2023
This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday July 10th, and 11th, written by Joe Slomka.
The Sun sets at 8:35 PM; night falls at 10:46. Dawn begins at 3:16 AM and ends with the Sun rising at 5:27.
Sunday was the Last Quarter Moon, which resides in Aries and provides a moonless evening for both nights. Monday’s Moon set at 1:58 PM. Tuesday’s Moon rises at 12:55 AM in the East, 42° high at 5 AM, 36% illuminated, 31 arc-minutes in size and sets at 3:09 PM; the Moon rises at 1:20 AM on Wednesday. Tuesday’s Dawn Moon leads 7° ahead of Jupiter and follows 6° behind on Wednesday.
Venus and Mars are closely parked together in Leo. By 9:15 PM, both are low on the western horizon. Venus is brightest, blazing with minus 4th magnitude, 39 arc-seconds in size, 24% lit, 11° high and sets at 10:16 PM. Red Planet Mars is dimmer, only 1st magnitude and 4 arc-seconds, 15° high and sets at 10:38 PM. Those with unobstructed horizon can see Mars and Venus 4° apart and Regulus (Leo’s heart) only 40 arc-minutes away. Mars and Venus fit within 5° telescope field on both nights; Mars is almost the same brightness as Regulus. Venus remains about 5° from Regulus until July 25, an event called a quasi-conjunction.
Mercury is still too close to the Sun; it sets during Civil Dawn.
Saturn is highest in southern Aquarius at 4:19 AM, glows with zero magnitude, 18 arc seconds and 35° high at 5 AM. Neptune, in Pisces, lies 21° from Saturn, flickers with 8th magnitude, 2 arc-seconds and 44° highest at 5:35 AM.
Eastern Jupiter and Uranus share Aries. Jupiter glimmers with minus 2nd magnitude, 37 arc-seconds, rises at 1:18 AM and 39° high at 5 AM. Jupiter is close to the Moon. Wednesday, the moon Io begins an eclipse at 1:52 AM and ends at 5:21. Uranus ends the planet parade by rising at 1:52 AM, 5th magnitude, 3 arc-seconds 34° high and 11° above Jupiter.
The American South and West experienced heat waves of epic proportions. Forecasters used the phrase “Dog Days.” That expression harks back to antiquity. Although most people observe Canis Major (the Big Dog), in winter, it, and its brightest star, Sirius, rises just before sunrise. Mesopotamians, Egyptians, Greeks and Romans knew this. They viewed the constellation as a dog. The word “Sirius” comes from the Greek for “scorching.” Indeed, the star rises during the hottest time of the year for the Northern Hemisphere. These cultures considered the constellation bad news. Heat was reputed to cause people and animals to become feverish, mad or warlike. Myths say men turned into werewolves, while animals contracted rabies. Today, we see the star a brilliant white; some ancient astronomers saw it as “reddish.” When Sirius first rises, it is, of course, low on the horizon, and appears red, just like a newly risen Sun. Egyptians did find one bright spot during the “Dog Days”. The rising of Sirius also signaled the beginning of the annual Nile floods. These floods not only irrigated farms but also deposited vital nutrients, fertilizing the soil.