Free Astronomy Magazine May-June 2020

MAY-JUNE 2020 planet-forming disks around very young stars in the Orion Clouds. These im- ages reveal new de- tails about the birthplaces of plan- ets and the earliest stages of star forma- tion. Most of the stars in the Universe are accompanied by planets. These plan- ets are born in rings of dust and gas, called protoplane- tary disks. Even very young stars are sur- rounded by these disks. Astronomers want to know ex- actly when these disks start to form, and what they look like. But young stars are very faint, and there are dense clouds of dust and gas surrounding them in stellar nurs- eries. Only highly sensitive radio tele- scope arrays can spot the tiny disks around these infant stars amidst the densely packed ma- terial in these clouds. For this new research, astronomers pointed both the Atacama Large Millimeter/sub- millimeter Array (ALMA) and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to a region in space where many stars are born: the Orion Molecular Clouds. This survey, called VLA/ ALMA Nascent Disk and Multiplicity (VANDAM), is the largest survey of young stars and their disks to date. Very young stars, also called proto- stars, form in clouds of gas and dust in space. The first step in the forma- tion of a star is when these dense clouds collapse due to gravity. As the cloud collapses, it begins to spin – forming a flattened disk around the protostar. Material from the disk continues to feed the star and make it grow. Eventually, the left- over material in the disk is expected to form planets. Many aspects about these first stages of star formation, and how the disk forms, are still unclear. But this new survey provides some miss- ing clues as the VLA and ALMA peered through the dense clouds and observed hundreds of proto- stars and their disks in various stages of their formation. “This survey revealed the average mass and size of these very young protoplanetary disks,” said John Tobin of the National Radio Astron- omy Observatory (NRAO) in Char- lottesville, Virginia, and leader of the survey team. “We can now com- pare them to older disks that have been studied intensively with ALMA as well.” What Tobin and his team found, is that very young disks can be similar T his image shows the Orion Molecular Clouds, the target of the VANDAM survey. Yellow dots are the locations of the observed protostars on a blue background image made by Herschel. Side panels show nine young protostars imaged by ALMA (blue) and the VLA (orange). [ALMA (ESO/NAOJ/NRAO), J. Tobin; NRAO/AUI/NSF, S. Dagnello; Herschel/ESA] SPACE CHRONICLES