Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.
Find more columns by Westlake here.
What’s that really bright star rising over the eastern mountains shortly after darkness falls this month?
Trick question — it’s not a star at all. It’s the giant planet Jupiter, the largest planet in our solar system. The gap between Earth and Jupiter has been closing in the past few months, and the two planets will be as close together as possible on the night of Oct. 28 — just 371 million miles apart. That is the night of Jupiter’s opposition, when the Earth passes directly between the giant planet and the sun.
Rising when the sun goes down, Jupiter will cross our sky all night long and set just as the sun rises. After Oct. 28, the distance between Earth and Jupiter will grow a little each day, but it still will be a constant companion in our evening sky throughout the remainder of the year.
As Jupiter approaches opposition, it is slowly slipping westward from night to night against the stars of Aries the Ram, not far from the Pleiades, or Seven Sisters, star cluster. The nearly full harvest moon will rise alongside Jupiter on the nights of Oct. 12 and 13 — a gorgeous sight to behold.
Do you own a pair of binoculars? If you do, try aiming them at Jupiter and you might glimpse one or two of Jupiter’s four giant moons: Io, Europa, Ganymede and Callisto. A small telescope will show them even better. The great Italian astronomer Galileo Galilei discovered these moons in 1610 when he first aimed his telescope toward the dazzling planet. It’s fascinating to watch the moons dance around Jupiter, changing their positions from night to night. The night of Oct. 18 will be a particularly good night to observe the moons as all four will be near their greatest elongations from the planet and easiest to see.
Jupiter is a totally different kind of planet than Earth. It is a colossal ball of hydrogen and helium gas, held together by its enormous gravity. Jupiter has no solid surface to stand on. If you tried to land on it, you would just sink down into its deep atmosphere and eventually splash down into an ocean of liquid hydrogen, thousands of miles deep. NASA’s Juno spacecraft is on its way to Jupiter right now and will arrive in 2016 to study Jupiter’s internal structure and composition.
With your telescope, you should be able to see alternating light and dark cloud stripes in Jupiter’s atmosphere, and you might glimpse its famous earth-sized storm, the Great Red Spot. Spot Jupiter for yourself in the eastern sky this month after 9 p.m.
Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published all across the world. Check out his website at www.jwestlake.com.