Skywatch Line for Monday and Tuesday, July 29th and 30rd, written by Joe Slomka

This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday, July 29th and 30rd, written by Joe Slomka.

The Sun sets at 8:19 PM; night falls at 10:17. Dawn begins at 3:47 AM and ends with sunrise at 5:45.

The Moon resides in eastern Taurus on both nights. Monday’s Moon rises at 12:11 AM and appears 31 arc-minutes in size and sets at 3:42 PM. Tuesday’s rises at 12:45 AM, 31° high at 4 AM, 26% illuminated and sets at 4:55 PM; the Pleiades star cluster can be found 6° below Tuesday’s Moon. Wednesday’s Moon rises at 1:29 AM, is 22° high at 4 AM and 17% lit.

Venus and Mercury appear 10° apart in western horizon’s Leo. Venus is the first to set at 9:03 PM, only 15° from the Sun, blazes with minus 4th magnitude, 10 arc-seconds, 96%lit and 11° high at 8 PM. Mercury follows, glowing with 1st magnitude, 9 arc-seconds, 12° high, 31% lit and sets at 9:07 PM.

Saturn is next, in southern Aquarius at 10:07 PM, first magnitude, 18 arc-seconds, and 41° high at 4 AM. Southern Neptune, 11° from Saturn, rises at 11:28 PM, 8th magnitude, 2 arc-seconds and 46° high.

Eastern Taurus gathers together Uranus, Mars and Jupiter. Uranus rises at 12:48 AM, 5th magnitude, 3 arc-seconds, 35° high at 4 AM. Mars rises at 1:19 AM, 1st magnitude, 5 arc-seconds and expanding, 23° high and 89% lit.

Gas Giant Jupiter is last, 7° from Mars, rises at 1:48 AM, minus 2nd magnitude and 23° high. Jupiter is finally able to present its
Moons. On Wednesday, the moon Europa begins a transit of its shadow at 12:16 AM and ends at 3:04 AM. The Great Red Spot becomes visible at 12:53. A multitude of moons begin their transit at 12:53 and ends at 2:45 AM.

This summer, the country experienced heat waves of epic proportions. Television 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. Ancient Mesopotamians, Egyptians, Greeks and Romans knew this. All named 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. The 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; however, 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. The Egyptians did find one bright spot during the Dog Days. The rising of Sirius signaled the beginning of annual Nile floods. These floods not only irrigated farms but also deposited vital nutrients, fertilizing the soil.