A planet-forming disk still fed by the mother cloud

Stellar systems like our own form inside interstellar clouds of gas and dust that collapse producing young stars surrounded by protoplanetary disks.

Planets form within these protoplanetary disks, leaving clear gaps, which have been recently observed in evolved systems, at the time when the mother cloud has been cleared out.

ALMA has now revealed an evolved protoplanetary disk with a large gap still being fed by the surrounding cloud via large accretion filaments.

This shows that accretion of material onto the protoplanetary disk is continuing for times longer than previously thought, affecting the evolution of the future planetary system.

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Credit: MPE

This false-color image shows the filaments of accretion around the protostar [BHB2007] 1. The large structures are inflows of molecular gas (CO) nurturing the disk surrounding the protostar.

The inset shows the dust emission from the disk, which is seen edge-on. The "holes" in the dust map represent an enormous ringed cavity seen (sideways) in the disk structure.

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Credit: MPE; illustration: Gabriel A. P. Franco

Two different observations of the protoplanetary disk show signatures of the formation of a companion to the protostar .

The gray scale represents the dust thermal emission from the disk, same as in the inset of Fig. 1. The red/blue contours show the molecular CO brightness emission levels from the northern/southern side of the dust cavity observed with ALMA. The brighter CO emission from the south indicates that the gas is hotter there.

This location coincides with a zone of non-thermal emission tracing ionized gas (green contours) observed with the VLA (middle), which is observed in addition to the protostar (center of the image).

The team proposes that both the ionized gas and the hot molecular gas are due to the presence of a protoplanet or a brown dwarf in the cavity. The configuration of such a system is shown in the sketch on the right.

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Formation of Planets in a Protoplanetary Disk

The artist conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas.

Debris coalesces to create rocky 'planetesimals' that collide and grow to eventually form planets.

The results of this study show that small planets form around stars with a wide range of heavy element content suggesting that their existence might be widespread in the galaxy.

Star's Planet-Forming Disc Revealed In Unprecedented Detail

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have delivered stunning imagery of the star HL Tauri and its protoplanetary disc.

According the European Southern Observatory, they are the "sharpest pictures ever made at submillimetre wavelengths."