Astronomers have found a compact solar system whose planets line up in a way that, according to current models, should not be possible. Around the small star LHS 1903, a dense rocky world orbits on ...

The Radcliffe wave. The clouds that comprise this structure are highlighted in red and superimposed on an artist's illustration of the Milky Way. The location of the sun is highlighted by the yellow ...

Active small bodies—including comets, active asteroids, icy minor planets, and transitional objects—occupy a unique position in planetary science. As ...