This is the Skywatch Line for Monday and Tuesday, June 11th and 12th.
The Sun sets at 8:34 PM; night falls at 10:49. Dawn begins at 3 AM and ends with the Sun rising at 5:16.
The early evening sky contains two planets. Venus, in Gemini, blazes with minus 4th magnitude, appears 76% illuminated and lies about 20º above the western horizon. One can enjoy Venus either through binoculars or a telescope. Telescopes provide more detailed views of its crescent. When the observer is finished looking at Venus, he can scan about 8º to Venus’ left to see the Beehive star Cluster. Views through binoculars or telescope are enjoyable, especially for the first-time sky gazer. Venus sets at 11:09 PM.
Jupiter is high in the South, shining with minus 2nd magnitude and appearing 29º high. It is best observed at about nightfall. Telescopic observers can see its moon Europa disappear behind Jupiter at 12:38 AM Tuesday. They can also see the Great Red Spot at 1:16 AM on Wednesday. Jupiter sets at 3:28 AM.
Twilight’s end sees the arrival of Saturn and 4Vesta in the southeastern sky. Rising at 9:30 PM, Saturn is easily spotted, shining with zero magnitude in the top of the “Teapot.” Saturn occupies 18 arc-seconds in our telescopes and appears 11º high. The asteroid 4Vesta lies about 7º above Saturn and shines with 5th magnitude, but is a tiny 0.6 arc-seconds in our eyepieces. It rises at 8:49 PM and is best observed at 1:36 AM. Vesta is steadily brightening and growing larger in preparation for its Opposition next week. Observers need detailed star charts from astronomy magazines or websites to find Vesta.
Midnight adds Mars. It rises at 11:39 PM and is best observed about 4:18 AM. Mars shines with minus 1st magnitude and appears about the same size as Saturn. Mars too is growing brighter, larger and nearer in advance of its own Opposition in July.
Finally, the waning 28-day-old Moon rises at 4:32 AM on Tuesday. It shines at minus 2nd magnitude and is about 3% lit. It hovers about 1 degree above the eastern horizon. Wednesday, the Moon turns officially “New” at 3:43 PM and is invisible in that night’s sky.
Planet Pluto is hosted by Sagittarius. While it is possible to see this distant body in an eight-inch telescope, most people need to observe from a dark rural area and have a larger telescope, as well as a very detailed star chart.
In the late 18th and early 19th Centuries, the planets Uranus and Neptune were discovered. Their orbits hinted another body out there. Percival Lowell, a wealthy Chicago magnate, funded his own observatory at Flagstaff, Arizona. The staff was tasked 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 the far 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 knowledge about Pluto. It is about 2370 KM (1472 mi) in diameter – smaller than the Moon. Pluto rotates backwards once every 6.4 days. It is covered by methane ice, has mountains and fields of ice flows. Charon is the largest of its 5 satellites.
Pluto glows with 14th magnitude, is 3º high at nightfall and is 0.1 arc-second in size. It rises at 10:26 PM and is bestobserved at 3:06 AM. It is currently located 32.5 times the Earth-Sun distance.