Chemical traces of a hidden world: Silicon sulfide hints at a protoplanet in the PDS 66 disk

Star system: MP Musca | Distance from the Sun: 319 light years

Astronomers using the ALMA telescope have detected rare molecules of silicon sulfide (SiS) in the dusty disk surrounding the young star PDS 66. This chemical signature is highly unusual because these molecules normally freeze onto dust grains in the cold reaches of a planetary system. 

The detection of a warm, compact source of SiS gas about 60 astronomical units from the star suggests the presence of a 'protoplanet'—a planet still in the process of forming. This growing world likely has a warm gaseous envelope that is melting surrounding dust and pebbles, releasing silicon into the gas phase. This finding provides a rare chemical 'map' to help scientists understand how giant pebbles eventually transform into fully grown planets.

Scientific study

A Protoplanet Candidate in the PDS 66 Disk Indicated by Silicon Sulfide Isotopologues (external link)