ALMA: Exciting Structures in a Young Protoplanetary Disk

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ALMA: Exciting Structures in a Young Protoplanetary Disk

Post by bystander » Wed Jun 20, 2018 6:13 pm

ALMA Discovers Exciting Structures in a Young Protoplanetary Disk That Support Planet Formation
ALMA | ESO | NAOJ | NRAO | 2018 Jun 20
Click to view full size image 1 or image 2
ALMA image of the 0.87 mm continuum emission from the MWC 758 disk. Various disk
structures are marked. The green dotted contours mark the boundaries of the disk; the
small circle at the center roughly marks the location of the star; the two green solid
contours represent the extent of the two bright clumps; the solid, dotted and dashed
white arcs trace out the inner, middle, and outer rings, respectively; and the arrow
points out the spiral arm. The resolution (beam size, ~6.5 AU) of the image is labeled
at the lower left corner. (Credit: ALMA (ESO/NAOJ/NRAO)/Dong et al.)

Astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to discover the tale-telling signs of planets in the young, likely planet-forming disk around the star MWC 758. They obtained an “ultra” high-resolution image revealing the disk having not only an off-centered cavity but also a spiral arm corresponding to one previously seen in reflected light.

“What drives the various kinds of structures we see in planet-forming young disks around protostars? This is a question that has baffled astronomers for over a decade!”, pointed out by the lead author of this investigation, Ruobing Dong, at University of Arizona, USA, and Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Taiwan; “Our observations reveal a great amount of exciting new details in this system and provide crucial clues on their origins.”

Since early 2000, rich structures, including gaps and rings, dust clumps, and spiral arm-like features, have been discovered in a few tens of disks surrounding newborn stars. With the belief that planets are forming inside, astronomers named these disks protoplanetary disks.

The origin of these structures is in hot debate among astronomers. In one scenario, they are thought to be produced by unseen planets forming inside and gravitationally interacting with the host disks, as planets open gaps, shepherd dust clumps, and excite spiral arms.

Alternative ways to produce observed disk structures that do not invoke planets have also been raised. For examples, large central cavities may be the outcome of photoevaporation, as high energy radiations from the central star evaporate the inner disk. Also, under certain conditions shadows in disks may mimic the spiral arms seen in reflected light. ...

The Eccentric Cavity, Triple Rings, Two-Armed Spirals, and Double Clumps of the MWC 758 Disk - Ruobing Dong et al
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