Driftless Dark Skies: Jupiter

March 4, 2016 by John Heasley

 Jupiter is at opposition on March 8 when it’s at its closest to Earth.  It will rise in the east at sunset, pass high overhead in the south at midnight, and set in the west at sunrise.  Jupiter blazes brighter than any star (twice the brilliance of Sirius) which makes it very easy to spot in the night sky. 

hotspot_cover_1280With a small telescope or binoculars on a tripod, you can make out some of the darker cloud belts in Jupiter’s atmosphere and maybe even the Great Red Spot.  You should also be able to spot small “stars” off to the side of Jupiter.  These are the four largest of Jupiter’s 67 moons: Io, Europa, Ganymede, and Callisto.  Ganymede is the largest moon in our solar system, even bigger than the planet Mercury.  Europa is especially intriguing since its one of the leading candidates for finding life beyond Earth.  It may have all three of the necessary requirements for life: liquid water, energy source, and organic compounds.  We might know better by the 2020s when NASA has plans to send a robot to orbit and land on Europa. 

Galileo was the first to turn a telescope to Jupiter.  He was astounded by what he saw.  In just one week in January 1610, he saw four “stars” in a line by Jupiter appearing and disappearing as they changed position.  The astronomical writings of Copernicus, Kepler, and Newton are important works, but I don’t usually recommend them for recreational reading.  Galileo’s Starry Messenger (Siderius Nuncius) is an exciting story to read.  Galileo tells how his “confusion was transformed to amazement” as he figured out what he was seeing: “Now we have not just once planet rotating around another while both run through a great orbit around our Sun; our own eyes show us the four stars which wander around Jupiter as does the Moon around the Earth, while all together trace out a grand revolution about the Sun in the space of twelve years.” 

Jupiter has been visited by robot explorers such as Pioneer, Voyager, Ulysses, Galileo, Cassini, and New Horizons.  Juno is on its way and will arrive at Jupiter on July 4 this summer.  But you can visit Jupiter any spring night in the Driftless Area and see it with your own eyes as Galileo did.  Kickapoo Valley Reserve astronomy educators will have a telescope set up on March 18 as part of the Equinox Stargaze.  Look for Jupiter just above the waxing gibbous Moon on March 21.  On the evenings of March 7 and 14, you can watch the shadows of Europa and Io crossing the cloud tops of Jupiter.  It gives us a chance to imagine the volcanoes erupting on Io and to ponder the strange creatures that might be dwelling in the seas of Europa. 

John Heasley is an astronomy educator and stargazer who enjoys connecting people with the cosmos. He volunteers with NASA/JPL as a Solar System Ambassador. For more information about stargazing in southwest WI, like Driftless Stargazing LLC on Facebook and find out whenever there’s something awesome happening in the skies. Driftless Dark Skies appears monthly in the Voice of the River Valley.