Astro Glossary

Ring Nebula, M57

A planetary nebula in the constellation Lyra.

Rocketry

Roman Empire

Rosetta Mission

A European Space Agency mission to explore Comet 67P/Churyumov–Gerasimenko. Launched in 2004, the craft arrived in 2014, becoming the first spacecraft to orbit a comet. Rosetta, which will study the comet through the end of 2015, as the comet moves closer to the Sun, also carries a small probe to land on the comet.

Royalty

Runaway Star

A runaway star is moving through the galaxy at a far greater speed than any of the other stars around it. In some cases, the star is moving fast enough to escape the Milky Way Galaxy and enter intergalactic space. A runaway may get a "kick" when it passes close to the supermassive black hole at the center of the galaxy, or when a companion star explodes as a supernova. Many runaway stars leave a "wake" as they plow through the gas and dust scattered between the stars.