This week in Astronomy and Physics

Astrophysics: A strange ménage à trois

Images of a fourth planet orbiting HR 8799

A Giant Planet Around a Metal-Poor Star of Extragalactic Origin

Cassini Finds an Oxygen–Carbon Dioxide Atmosphere at Saturn’s Icy Moon Rhea

Crossover between Kelvin-Helmholtz and counter-superflow instabilities in two-component Bose-Einstein condensates

Pions in Large N Quantum Chromodynamics

Three-Dimensional Light Bullets in Arrays of Waveguides

Herschel-ATLAS: Rapid evolution of dust in galaxies in the last 5 billion years