The Ellensburg, WA sky for the week of June 4, 2022

Saturday: You know Metis and Thebe and Adrastea and Amalthea. Io and Ganymede and Callisto and Europa. But do you recall? There are 79 Jovian moons in all. Just 60 years ago, Jupiter was thought to have only 12 moons. But, astronomers are red-nosed with delight that the advent of supersensitive electronic cameras has caused the number of discovered moons to rapidly increase. Jupiter’s 79 moons range in size from Ganymede, the largest in the Solar System with a diameter of 5,262 kilometers, to numerous moons with diameters of only one kilometer. Recently, Saturn moved into first in the moon race with 82. Uranus is next with 27. Then comes Neptune with 14, Mars with 2, and Earth with 1. Our moon is the fifth largest in the Solar System, with a diameter of 3,475 kilometers. (One kilometer is 0.62 miles.) Even dwarf planets have moons. Pluto has 5, Eris has 1, Haumea has 2, and Makemake has 1. Eris is an outer solar system object that was discovered in 2005 and named in September of 2006. Because astronomers thought it was larger than Pluto, people called it the tenth planet for a while. (More recent measurements show Eris to be a little smaller in diameter than Pluto.) Haumea, the newest dwarf planet with a moon, was discovered in 2004 and officially named a dwarf planet on September 17, 2008. Go to https://solarsystem.nasa.gov/moons/ for more information about Solar System moons.

Sunday: Summer is nearly here. How do I know? Because the days are very long. Because the temperature is rising. Because the school year is ending. Also, because the Summer Triangle is fairly high in the eastern sky at 11:00 p.m. Vega, the third brightest star visible from Ellensburg, is about five fists above the east horizon. Deneb, at the tail of Cygnus the swan is about three and a half fists above the east-northeast horizon. The third star in the triangle, Altair in Aquila the eagle, is nearly two fists above the east horizon.

If you want to put somebody off, tell her to wait until Deneb sets. At Ellensburg’s latitude of 47 degrees, Deneb is a circumpolar star meaning it never goes below the horizon.

Monday: Antares is one and a half a fists above the south-southeastern horizon at 11:30 p.m.

Tuesday: In 1982, the British group Bow Wow Wow first sang, “I Want Candy”. In May 2019, NASA finally granted that wish by releasing images of Mars’ moon Phobos looking like candy. The thermal imaging camera on NASA’s long lived Odyssey orbiter took a series of images of the full phase of Phobos. The resulting composite, looking like a many layered jaw-breaker, shows how the temperature varies throughout the small moon. This temperature distribution, in turn, can help astronomers determine what the moon is made of. For more about this yummy treat, go to https://www.jpl.nasa.gov/news/why-this-martian-full-moon-looks-like-candy. Mars is in the pre-dawn sky with many other planetary treats. At 4:30 a.m., Mercury is just rising above the east-northeastern horizon. Venus is nearly a fist above the eastern horizon, the brightest point of light in the morning sky. Jupiter, the second brightest point of light, is two fists above the east-southeastern horizon. Mars is about a half a fist to the lower left of Jupiter. Finally, Saturn is two fists above the south-southeastern horizon.

Wednesday: The bright star Capella is a half a fist above the north-northwestern horizon at 11:30 p.m. Interestingly enough, it is only about two fists from the Sun. If you viewed Capella from Ketchikan, the southernmost city in Alaska, Capella would be one and a half fists above the horizon. The Sun would be close enough to the horizon that there would be a twilight glow.

Thursday: The bright star Spica is a half a fist below the moon in the southern sky at 10:00 p.m.

Friday: It looks so peaceful up there. But life is not peaceful for Jupiter. According to a recent study by astronomers, Jupiter gets hit by a 5-20 meter diameter asteroid 10 to 65 times a year. For comparison, the object that exploded over the Russian city of Chelyabinsk in 2013 was 20 meters in diameter. Earth gets hit by a 20-meter asteroid about once every 50 years. For more information, go to https://goo.gl/RxPc5G. Jupiter is two fists above the east-southeastern horizon at 4:30 a.m.

 
The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.