Nestled in the Ophiuchus star-forming region, approximately 410 light-years from the Sun, a fascinating protoplanetary disk around the young star AS 209 is slowly being carved into shape.
Artist’s impression of an infant star still surrounded by a protoplanetary disk in which planets are forming. Image credit: L. Calçada / ESO.
Protoplanetary disks 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, the protoplanetary system AS 209 is very young, but already two clear gaps are being sculpted from the disk.
Italian astronomer Davide Fedele and co-authors used the Atacama Large Millimeter/submillimeter Array (ALMA) to study this system in great detail.
The researchers captured a high-resolution image of AS 209’s protoplanetary disk, which shows dust particles that scatter the light from the central star.
“The dust continuum emission is characterized by a main central core and two prominent rings at 75 and 130 astronomical units (AU) intervaled by two gaps at 62 and 103 AU,” they said.
“The two gaps have different widths and depths, with the inner one being narrower and shallower.”
This wonderful image was captured using ALMA, revealing a curious pattern of rings and gaps in the dust surrounding the young star AS 209. Image credit: ALMA / ESO / NAOJ / NRAO / D. Fedele et al.
The outer gap is deep, wide, and largely a dust-free zone, leading Dr. Fedele and his colleagues to believe that a giant planet with 0.7 Saturn masses is orbiting there.
“The Saturn-like planet is around 103 AU from the central star — more than 3 times the distance between Solar System’s Neptune and the Sun,” the astronomers said.
“As the planet carves out its path, dust piles up at the outer edge of its orbit, creating ever more defined rings in the protoplanetary disk.”
“The thinner, inner dust gap could have been formed by a smaller planet, but the more intriguing possibility is 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 disks on particularly short timescales,” they said.
The findings appear in the journal Astronomy & Astrophysics (arXiv.org preprint).
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D. Fedele et al. 2018. ALMA continuum observations of the protoplanetary disk AS 209. Evidence of multiple gaps opened by a single planet. A&A 610, A24; doi: 10.1051/0004-6361/201731978
