ALMA image of the planet-forming disk around the young star RU Lup, showing a giant set of spiral arms made out of gas. The structure extends to nearly 1000 astronomical units from the star.
ALMA image of the planet-forming disk around the young star RU Lup. The inset image (lower left, red disk) shows a previous (DSHARP) observation of the dust disk with rings and gaps that hint at the presence of forming planets. The new observation shows a large spiral structure (in blue), made out of gas, that spans far beyond the compact dust disk.