This is the Skywatch Line for Monday (Memorial Day) and Tuesday, May 27th and 28th, written by Joe Slomka.
The Sun sets at 8:23 PM; night falls at 10:34. Dawn begins at 3:14 AM and ends with the Sun rising at 5:22.
Mars, in Gemini, continues as the easiest evening planet. Appearing 97% illuminated and shining with first magnitude, the Red Planet appears about 4 arc-seconds in size about 18º high in the West. It sets at 10:50 PM. Mercury hovers in the western constellation of Taurus. It shimmers with minus 1st magnitude, but is only 1º altitude, requiring an unobstructed horizon to be spotted. Mercury sets at 9:01 PM, but becomes easier in June.
Jupiter rises in Ophiuchus at 9:22 PM, glowing with minus 2nd magnitude, appearing a large 45 arc-seconds and 9º high. Jupiter is causing excitement among amateur and professional astronomers. The Skywatch Line has long mentioned the Great Red Spot (GRS), a giant storm on Jupiter. May 19th, Australian astronomers reported 10 thousand Km pieces of the GRS detaching and being carried away and dissipated by a nearby jet every week or so. These jets blow at about 350 Miles Per Hour. Smaller similar events have happened before in 2017. The GRS has been shrinking for a while. Once 3 Earths wide, it now is only about the size of our planet. The GRS will be visible at 1:37 AM on Wednesday. Jupiter is nearing its June Opposition, which makes it ideal for amateurs with 6” or larger telescopes to follow this event. Astronomy websites are covering this event with regular updates. Jupiter sets at 1:55 AM.
Dwarf Planet 1Ceres shares Ophiuchus with Jupiter. Ceres experiences its own Opposition Tuesday night, making it the ideal time to examine this largest asteroid and brightest dwarf. Ceres is differentiated into layers; it has a rocky core, but icy crust and surface. It is about 25% ice. Ceres glows with 7th magnitude and is a tiny 0.7 arc-seconds in size, making observation easier for binoculars or small telescope. It rises at 8:16 PM and is best observed at 1:07 AM. Finder charts are available from various astronomical websites.
Saturn rises in Sagittarius at 11:22 PM. It shines with zero magnitude and appears about one-third Jupiter’s size. By midnight, is it only 5º high, but 24º at Dawn. It is best observed at 4:00 AM.
Blue-green Neptune rises in Aquarius at 2:10 AM. It smolders with 8th magnitude, appearing about 2 arc-seconds in size. Finder charts also assist in locating this distant member of our Solar System.
The waning Moon shares Aquarius with Neptune on Tuesday. At 24-days-old, it appears about 35% lit and blazing with minus 8th magnitude and rises at 2:44 AM. Wednesday, finds a slimmer Moon rising at 3:09 AM in Cetus. It is about 26% lit, and slightly dimmer. Wednesday’s Moon is found between Neptune and Uranus.
Uranus also shares Aquarius with Neptune and the Moon. Rising at 3:51 AM, it shines with 5th magnitude and is 9º high at Civil Dawn. Venus brings up the rear, in Aries. Rising at 4:26 AM, it appears about 93% lit and shines with minus 3rd magnitude, but only 3º above the eastern horizon. Both planets are rising in the increasingly sunlit eastern sky. Observers should try for them as early as possible.