Nestled in the young Ophiuchus star-forming region, 410 light-years from the Sun, a fascinating protoplanetary disc named AS 209 is slowly being carved into shape. This wonderful image was captured using the high-resolution ALMA telescope, revealing a curious pattern of rings and gaps in the dust surrounding a young star.
Protoplanetary discs are dense, rotating planes of gas and dust that surround newly formed stars; providing the matter that one day becomes orbiting planets, moons, and other minor bodies. At less than one million years old, this system is very young, but already two clear gaps are being sculpted from the disc.
The outer gap is deep, wide, and largely a dust-free zone, leading astronomers to believe that a giant planet almost the mass of Saturn is orbiting here — around 800 light-minutes from the central star, and more than three times the distance between Neptune and the Sun! As the planet carves out its path, dust piles up at the outer edge of its orbit, creating ever more defined rings in the disc. The thinner, inner dust gap could have been formed by a smaller planet, but astronomers have raised the intriguing possibility that the large and distant circling planet in fact created both paths.
This inferred Saturn-like planet so far from its central star raises fascinating questions about planet formation at the edges of protoplanetary discs on particularly short timescales.
Reference: “ALMA continuum observations of the protoplanetary disk AS 209. Evidence of multiple gaps opened by a single planet” by D. Fedele1, M. Tazzari, R. Booth, L. Testi, C. J. Clarke, I. Pascucci, A. Kospal, D. Semenov, S. Bruderer, Th. Henning and R. Teague, 22 February 2018, Astronomy & Astrophysics.