moon wobble

A Polar Ice Cap?

On April 29, NASA released a series of images showing broad areas of light and dark surface features on Pluto. A bright patch near the north pole was described as “suspiciously suggestive of a polar cap.” These images have been stabilized so Pluto remains centered, with a line showing the orientation of the planet’s north pole. In reality, the gravity of the large moon Charon makes Pluto wobble.


In the NFL, something that behaves like Pluto’s football-shaped moons might be called a wobbly duck. NASA simply calls them astonishing.

Instead of steadily rotating through their orbits, two of Pluto’s moons “wobble unpredictably,” the space agency says, citing new analysis of data from the Hubble Space Telescope.

The two moons, Hydra and Nix, are the largest of the four moons that move around Pluto and Charon — the “double planet” that is the destination of next month’s visit by NASA’s New Horizons spacecraft.

Pluto’s Moons Are ‘Tumbling In Absolute Chaos,’ NASA Says

Photo credit: M. Showalter (SETI)/G. Bacon (STScI)/NASA/ESA


Pluto has one large moon, Charon, and four smaller moons: Styx, Nix, Kerberos, and Hydra. Pluto and Charon actually orbit around each other because they are pretty similar in size. The four smaller moons spin wildly around the planetary system. Hydra, for example, rotates 89 times as it completes one trip around Pluto. T

he moons also wobble like “spinning tops,” thanks to the gravitational pulls of both Pluto and Charon. NASA thinks that the four wobbly moons are the results of mergers of two or more moons — meaning Pluto once had even more satellites than it does now.

— Loren Grush for The Verge