Observing Something Rare

Astronomers have observed a rare instance of a solar system inside the Milky Way whose planets orbit in sync around their host star, according to a study published yesterday. Researchers believe the motion of the planets has remained virtually unchanged since the system's formation roughly 4 billion years ago.

The four closest planets display what is known as 3:2 resonance—for every three orbits a planet makes around the host star, the next farthest planet completes two orbits. The next two planets display a similar 4:3 resonance. Typically, newborn systems are knocked out of balance by some disruptive event (for example, collisions with asteroids). Because the planets in question have maintained their original orbits, their study is expected to shed light on the early stages of star system formation.

The host star is also the brightest discovered to date to have more than four planets orbiting around it. Visualize the motion of the six planets here.