A new analysis of the ALMA data for a young star HL Tauri provides yet more firm evidence of baby planets around the star. Researchers uncovered two gaps in the gas disk around HL Tauri. The locations of these gaps in the gas match the locations of gaps in the dust found in the ALMA high resolution image taken in 2014. This discovery supports the idea that planets form in much shorter timescales than previously thought and prompts a reconsideration of alternative planet formation scenarios.
In November 2014, ALMA released a startling image of HL Tauri and its dust disk. This image, the sharpest ever taken for this kind of object, clearly depicts several gaps in the dust disk around the star.
Astronomers have not yet reached a definitive answer for what makes the gaps in the dust disk. Because these disks are the sites of planet formation, some suggest that infant planets are the key; the dark gaps are carved by planets forming in the disk that attract or sweep away the dust along their orbits.
But others doubt the planet explanation because HL Tauri is very young, estimated to be only about a million years, and classical studies indicate that it takes more than tens of millions of years for planets to form from small dust. Those researchers propose other possible mechanisms to form the gaps: changes in the dust size through coalescence or destruction; or the formation of dust due to gas molecules freezing.