Twilight: New Moon(s)
Did I trick any Twilight lovers out there? Sorry to disappoint you fan-pires, but this post is not about the movie, but about today being the birthday anniversary of astronomer Charles Dillon Perrine. Twilight: New Moon might not have been around when Charles Perrine was born in Ohio on July 28th in 1867, but Jupiter’s “new” moons made the astronomer famous when he discovered them in the early 1900’s.
While working at the Lick Observatory at the University of California, Perrine discovered Jupiter’s sixth moon, Himalia, in 1904 and Jupiter’s seventh moon, Elara, in 1905. Perrine later moved to Argentina, where he went on to be the director of the Argentine National Observatory.
Jupiter has a lot of moons. How many? 63! That’s right; Jupiter has 63 celestial bodies zipping around it all the time. And they aren’t all just little hunks of rock. Jupiter’s four most massive moons, known as the Galilean moons because there were discovered by Galileo, are some of the most massive objects in our solar system besides the Sun and eight planets. These moons are pretty cool.
The innermost Galilean moon, Lo, is just a little bit bigger than our moon. What makes Lo so cool (well, actually really hot), is that its surface is covered with more than 400 active volcanoes, making it the most geologically active object in our solar system. Lo’s surface has hundreds of mountains, many of which are taller than Mount Everest. Check out this article on Lo for an even more in-depth view.
Not all of Jupiter’s moons are as fiery as Lo, however. The second closest of the Galilean moons, Europa, is cool because it’s composed almost entirely of ice! This frigid moon is slightly smaller than our own moon, and scientists theorize that underneath its icy exterior is an ocean of liquid water. Scientists even think that this ocean could harbor life!
Jupiter’s next Galilean moon is big – really big. Ganymede is the largest moon in our solar system with a diameter of a whopping 5,268 kilometers, eight percent larger than the planet Mercury. It’s composed mostly of rock and ice, and is the only moon in the solar system with a magnetosphere, meaning Ganymede’s magnetic field dominates an area surrounding the moon. Ganymede possesses a thin atmosphere containing oxygen and ozone. Take a peek at this neat picture the Hubble Space Telescope took of Ganymede trying to hide behind Jupiter.
The Galilean moon most distant from Jupiter is Callisto. Like Ganymede, it is also made of rock and ice but scientists think that Callisto may have a liquid water ocean more than 100 kilometers below its surface that could harbor life. NASA scientists even chose to study Callisto because they thought it was a good site for a NASA refueling base, or even as a candidate planet for future human colonization! Here’s an article from NASA about their new proposal for a mission to explore Jupiter and it’s four Galilean moons.
To learn more about our super cool solar system, visit the Maryland Science Center and check out our awesome planetarium, observatory and “Our Place in Space” exhibit.
