This is the Skywatch Line for Monday and Tuesday, July 27th and 28th, written by Joe Slomka.
The Sun sets at 8:21 PM; night falls at 10:20. Dawn begins at 3:44 AM and ends with the Sun rising at 5:43.
Monday’s Moon is at First Quarter, rising at 1:39 PM in Libra, appearing 56% illuminated and setting at 12:33 AM, Tuesday. Tuesday’s Moon rises at 2:53 PM also in Libra, 67% lit and setting at 1:06 AM, Wednesday.
Comet NEOWISE is rapidly exiting our neighborhood; the comet is fading from 3rd magnitude to 4th. At 10 PM on both nights, the comet stands 27° high in the northwestern constellation of Ursa Major (the Big Bear). There are no major guide stars in the barren area between the Bear and the constellation’s border. The nearest bright star is Nu, a 3rd magnitude star below the comet. The Moon should be distant enough to permit views of NEOWISE, which sets at 1 AM.
Sagittarius houses the bright planets Jupiter and Saturn, and the dim dwarf planet Pluto. Jupiter rises at 5:05 PM and, by 9 PM, is 13° high in southeast, appearing 47 arc-seconds in size, glows with minus 2nd magnitude; it sets at 5 AM. Pluto, 3° away from Jupiter, rises next at 5:17 PM smolders with minus 14th magnitude and appears tiny; by 9 PM it is 11° high. Saturn, 7 ½° East of Jupiter, rises at 5:37 PM, glares with minus 2nd magnitude and appears 18 arc-seconds; by 9 PM, it is 10° high. Saturn just passed Opposition, which means it is at its brightest and best time to observe its beautiful ring system. Saturn sets after Sunrise.
Mars, in Pisces, rises at 10:41 PM, blushes with minus 1st magnitude, appears 14 arc-seconds and continues to brighten and enlarge in our instruments. The Red Planet is now the target of three separate space missions by the Chinese, United Arab Emirates and the US. Mars lies about 25° from Neptune and Uranus. Best observed at 4:42 AM, it sets after sunset.
Blue-green Neptune, in Aquarius, shines with 8th magnitude, appears 2 arc-seconds and rises at 9:02 PM. Uranus, in Aries, rises at 12:11 AM, shines with 5th magnitude and appears 3 arc-seconds in size. Star charts from various astronomical books and websites help in locating these distant members of our Solar System.
Venus, in Taurus, rises at 2:56 AM, blazes with minus 4th magnitude, appears 29 arc-seconds, 14° high in the pre-sunrise East at 4 AM and 40% lit. Mercury, in Gemini, rises at 4:44 AM, 66° degrees from Venus and glares with zero magnitude. By 5 AM, it stands 7° in the East and appears 57% lit.
This month, the Capital District experienced a heat wave. 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 described 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 as 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 also signaled the beginning of the annual Nile floods. These surges not only irrigated farms but also deposited vital nutrients, fertilizing the soil.