Pluto and Charon dance it off in the intergalactic smash hit “So you think you can orbit?” Can their perpendicular orbit help them win it all?
Listen here [2:02m]:
Download here [1.9 Mb]: ftp://space.mit.edu/pub/ajb/radiopio/astrofacts_090813_soyouthinkyoucanorbit.mp3
What’s the facts:
Pluto, the second-largest known dwarf planet in the Solar System (after Eris), and its largest moon, Charon, are sometimes treated as a binary system, because the center of their orbit does not lie within either body (Charon is about half as big and 1/7th as massive as Pluto). Indeed, before its re-classification, Pluto and Charon were the closest thing to a double planet known. The orbit of Pluto and Charon is also special in that it is nearly perpendicular to the plane of their mutual orbit around the Sun, like a record rolling on its side (Uranus and its moons are tilted over in a similar way). As such, the Pluto-Charon orbit can be seen either face-on – like a clock – or edge-on – like a thrown frisbee – during its 248-year trek around the Sun. Between 1985 and 1990 the orbit was aligned edge-on so that the two bodies repeatedly passed in front of each other, or eclipsed. These eclipses allowed astronomers to measure both the sizes of Pluto and Charon as well as make a rough map of Pluto’s surface features. Finally, Pluto and Charon are the only planet-moon pair whose orbit and rotations are mutual synchronized; that is, they both face the same face to each other all the time. This makes Pluto and Charon excellent partners as the dance their way through space!
Original air date 13 August 2009.