Skywatch Line for Monday and Tuesday, July 22nd and 23rd, written by Joe Slomka
This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday, July 22nd and 23rd, written by Joe Slomka.
The Sun sets at 8:26 PM; night falls at 10:29. Dawn begins at 3:36 AM and ends with sunrise at 5:05.
Monday’s Moon set at 6:40 AM and rises at 9:44 PM; just past Full Moon, by midnight is 19° high in the southeast, appears 33 arc-seconds in size, 96% illuminated and sets at 8:01 AM, Tuesday. By 4 AM, the Moon is 28° high, now in Capricornus, still 33 arc-seconds, 95% lit and sets at 9:20 AM, Wednesday.
Western Venus is the first plant to appear; in Cancer, the observer should begin as soon as possible after Civil Twilight (9 PM) since its very close to the horizon. Venus rose at 6:45 AM, by Civil Twilight, Venus is 13° from the Sun, blazes with minus 4th magnitude, 8 arc-seconds, 97% lit, but 1° above the horizon and sets at 9:07 PM. Western Mercury, in Leo, lies 13° below Venus, zero magnitude, 9 arc-seconds, 5° high, 44% lit and sets at 9:30 PM.
Saturn, near the Moon in southern Aquarius, rises at 10:35 PM Tuesday, shines with 1st magnitude, 18 arc-seconds, and by 4 AM it is 41° high. Neptune, 11° behind Saturn, rises at 10:55 PM, 7th magnitude, 2 arc-seconds and 44° high at 4 AM. Eastern Taurus houses Uranus, Mars and Jupiter. Uranus rises at 1:15 AM, 5th magnitude, 3 arc-seconds and 30° high. Mars, 5° behind Uranus, rises at 1:31 AM, 1st magnitude and brightening, 5 arc-seconds, 16° high. Finally, Jupiter appears, rising at 2:11 AM, minus 2nd magnitude, 34 arc-seconds and 19° high.
The night reveals two Dwarf Planets, 1Ceres and Pluto. Ceres is found low in southern Sagittarius; it rises at 7:46 PM, highest at 11:39 PM and sets at 3:37 AM. It flickers with 7th magnitude, very small 0.6 arc-second, by 9 PM it is 8° degrees high, 17° at midnight and 4° high at 3 AM. The other is Pluto, rises in southwestern Capricornus at 8:38 PM, 14th magnitude, 0.1 arc-seconds, highest at 1:08 AM and sets at 5:34. We mention this is because Tuesday morning finds Pluto in Opposition,(closest to the Sun). Pluto is small, dim and close to the horizon. Those with large telescopes and detailed charts may try for an observation.
In the late 18th and early 19th Centuries, Uranus and Neptune were discovered. Their orbits hinted another body out there. Percival Lowell, a wealthy Chicago magnate, funded his private observatory at Flagstaff, Arizona. Staff was charged with finding the elusive “Planet X.” After years of observation and sifting through thousands of photographs, Clyde Tombaugh found it. When Lowell Observatory announced the discovery in 1930, Pluto was seen as a lone planet in remote reaches of our Solar System. We now know Pluto is a member of the Kuiper Belt, which consists of asteroids and comets. Smaller than originally thought, it was reclassified a “dwarf planet” in 2006. In 2015, NASA’s New Horizons spacecraft changed our view of Pluto. It is about 2370 KM (1472 mi) in diameter – smaller than the Moon. Pluto rotates backwards once every 6.4 days, covered by methane ice, has mountains and fields of ice flows. Charon is the largest of its 5 satellites.
Clear Skies Joe Slomka