Solar System shapes and sizes

A comparison of the shapes and rotations of three Solar System bodies: Phoebe (left ), Vesta (center), and Mimas (right). Vesta is the second most massive object in the main asteroid belt, while Phoebe and Mimas are both moons of Saturn. Mimas has a diameter of 416 kilometers along its longest axis. I chose to order the objects by roundness, with Phoebe the most irregular and Mimas closest in shape to an ellipsoid. As the smallest body in this comparison, Phoebe's irregular shape isn't a surprise. Mimas is rounder than Vesta despite being significantly smaller--a colossal pair of impacts at Vesta's south pole is partly responsible for the asteroid's distinctive shape.

The orientation and rotation rates of all objects are accurate, with 'up' matching the direction of the Earth's north pole. Vesta rotates quickly, completing a rotation about once every five hours. Like our own moon, Mimas is in a synchronous rotation state, with a rotation period matching its orbital period of 22.6 hours. Phoebe is one of the rare moons that is not a synchronous rotator and has a swift--by moon standards--rotation period of about 9 hours.

The 3D shape models used in this visualization were derived from spacecraft imagery by Robert Gaskell.

Category:

Science & Technology

Tags:

• Astronomy
• Solar System
• space
• saturn
• asteroid
• moon