Traditionally, planet formation is a slow and gradual “bottom-up” process, in which small particles of interstellar dust aggregate over millions of years, growing from grains a few microns in size to planets of significant size.
However, planets can form rapidly through a process known as “top-down”. In this scenario, material in the discs of gas and dust surrounding young stars fragments into spiral structures due to gravitational instability; these fragments then condense into new planets.
Supporting this hypothesis is a study by an international team of astronomers led by the University of Victoria (Canada) in collaboration with researchers from the University of Milan and published in the journal Nature.
To reach their conclusions, the researchers used the Atacama Large Millimetre/submillimetre Array (ALMA), the world's most powerful radio telescope, which allowed them to study how gas moves in the vast spiral arms of the system.
Using the ALMA radio interferometer (12-metre array), the research team mapped the velocity of two carbon monoxide isotopologues (13CO and C18O) within these vast spiral arms around AB Aurigae and found clear evidence of the predicted “oscillations”.
The detection of gravitational instability in the disc around AB Aurigae is therefore direct observational confirmation of this ‘top-down’ pathway to planet formation.
Fascinating results that show us how many unsolved mysteries about the formation of planets can be solved thanks to technology.
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