English: This beautiful image, captured with the Atacama Large Millimeter/submillimeter Array (ALMA) features a protoplanetary disc surrounding the young stellar object Elias 2-27, some 450 light years away. ALMA has discovered and observed plenty of protoplanetary discs, but this disc is special as it shows two distinct spiral arms, almost like a tiny version of a spiral galaxy.

Previously, astronomers noted compelling spiral features on the surfaces of protoplanetary discs, but it was unknown if these same spiral patterns also emerged deep within the disc where planet formation takes place. ALMA, for the first time, was able to peer deep into the mid-plane of a disk and discovered the clear signature of spiral density waves.

Nearest to the star, ALMA found a flat disc of dust, which extends to what would approximately be the orbit of Neptune in our own Solar System. Beyond that point, in the region analogous to our Kuiper Belt, ALMA detected a narrow band with significantly less dust, which may be an indication for planet in formation. Springing from the outer edge of this gap are the two sweeping spiral arms that extend more than 10 billion kilometers away from their host star. The discovery of spiral waves at these extreme distances may have implications on the theory of planet formation.

Paper detailing Elias 2-27: http://science.sciencemag.org/content/353/6307/1519.full