Credit: ALMA (ESO/NAOJ/NRAO), S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello
This week’s Picture of the Week focuses on one of twenty protoplanetary discs explored and imaged by ALMA’s first Large Program, known as the Disk Substructures at High Angular Resolution Project (DSHARP).
The disc is called AS 209, and its substructures are particularly
pronounced thanks to its thin, high-contrast rings and almost face-on
orientation towards us.
Though concentric rings — shown
here in particularly beautiful clarity — are a common substructure among
such discs, their widths, separations, and number can vary greatly.
It’s still unclear how these substructures form, and how planets emerge
from them. Quantifying and studying these similarities and differences
was a motivator for constructing ALMA, and was the main objective of
DSHARP. These details may hold clues to the type of planetary system
that will eventually emerge.
One interpretation is that there may be a rapid and complex interplay between young protoplanets and the disc itself far earlier in the evolution of the planetary system
than previously thought. A leading theory of planet formation requires
dust within these discs to clump into grains, then pebbles, and
eventually planetesimals.
This theory has always been stumped, however, by the fact that once an
object reaches a certain mass, the dynamics of these discs would cause
it to be sucked into the host star at the centre, thus halting its
growth into a true planet. The results from the DSHARP program suggest
that disc substructures may perturb these dynamics and provide safe
havens where young planetesimals can continue growing — making the
substructures observed here crucial to our own existence.
Next
week’s picture will be the final instalment in the DSHARP series, and
will showcase another of the twenty images: this time a multiple star system.
Source: ESO/Potw
