We are going to jump ship here and head back toward Earth for a close-up on Jupiter.
Exploring Orion has been a lot of fun, but there is a lot to see around our local solar system as well. Jupiter is easy to spot even from the most light-polluted areas. Not long after sunset, looking to the east, you will see it breach the horizon. Jupiter appears as a very bright star with a faintly reddish hue. Whip out a simple pair of binoculars and you will easily spot the four large moons of Jupiter aligned in a row in different locations to the left, or right, of the planet. With a decent-size telescope, you can easily make out some of the storm bands.
While the origins of the first telescope are a bit of a mystery, it was first patented by Dutch eyeglass makers in 1608. The patent listed the telescope as a tool “for seeing things far away as if they were nearby.” Within a year, a man named Galileo Galilei heard about this invention and made one for himself. In doing so, he helped to catapult humanity into a new age of understanding. For reasons unknown, he decided to use this telescope to explore the night sky. He was the first person to document the rings around Saturn, the massive craters on the Moon, and the great red storm on Jupiter.
Galileo was a bit puzzled by what he saw when he looked at Jupiter with his new telescope. He saw what looked like four little stars that would switch positions on either side of Jupiter from night to night. Here is a sketch he made showing what he saw.
It didn’t take Galileo long to realize that these four “stars” were actually moons of Jupiter going in circles around the planet. This was a huge breakthrough in understanding, and it completely overturned conventional wisdom of the time. The four Galilean moons—Io, Europa, Ganymede, and Callisto—are easily spotted when looking at Jupiter with even basic binoculars.
When I sit out at night imaging Jupiter, I often imagine how Galileo would marvel at the modern scientific world he helped to create over 400 years ago. I feel fortunate to live in a time when I can set up a telescope in my front yard and explore Jupiter in ways of which Galileo could only have dreamed.
Currently, Jupiter has 67 known moons, of which the four Galilean moons are the largest.
Some simple and fun calculations to do with kids:
Earth is about 24,000 miles in circumference at the equator. It takes Earth about 24 hours to rotate one time. If you take 24,000 miles and divide it by 24 hours, you get a 1,000-miles-per-hour spin rate at the equator. So if you stand on the equator, you are moving at 1,000 miles an hour!
Jupiter, on the other hand, is 272,946 miles around at the equator and spins one time in about 10 hours! This is insanely fast. At the equator, Jupiter is spinning at around 27,000 miles per hour. The rotational speed is so fast that it is actually making the planet bulge out at the equator, giving it the appearance of a squished ball instead of a nice sphere. This also makes shooting images of it difficult, as it is rotating so fast that you have to capture your images in under 3 minutes or you will get blur from the rotation. Here is a link to a nice animation I was able to capture showing about 2 hours of rotation and two moons zooming by: http://rankinstudio.com/Jupiter_Rotation_10.31.12