Countless Protostars Discovered in the Orion Molecular Clouds

The majority of the stars in the Universe are chaperoned by planets, which are created in rings of dust and gas, known as protoplanetary disks.

These rings also surround incredibly young stars, and researchers are curious as to when these disks start to develop, and what they look like. However, young stars are very dim, and there are thick clouds of dust and gas encircling them in stellar birthplaces. Only highly sensitive radio telescope networks are able to see the small disks around these young stars surrounded by all that material.

Stars Form in Stages

In a new research, astronomers adjusted both the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimetre/Submillimetre Array (ALMA) to look at an area where numerous stars are born every day: the Orion Molecular Clouds. The study, called VLA/ALMA Nascent Disk and Multiplicity (VANDAM), is the most comprehensive survey of young stars and their disks to date.

Protostars, which are very young stars, take shape in clouds of dust and gas. The first stage in the development of a star is when the dense clouds shatter because of gravity. As the cloud collapses, it starts to rotate, creating a flattened disk that surrounds the protostar. Material from the disk keeps being consumed by the star, which, in turn, grows bigger. Ultimately, the remaining material in the disk is believed to form planets.

Numerous elements about these first steps of star formation, and the way the disk takes shape, are still unknown. However, this new observation offers some additional clues as the VLA and ALMA looked through the thick clouds and noticed hundreds of protostars and their disks in different stages of their development.

“This survey revealed the average mass and size of these very young protoplanetary disks,” said John Tobin of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, and lead of the researching team. “We can now compare them to older disks that have been studied intensively with ALMA as well.”

The Accuracy and Sensitivity of the Instruments Made it Possible

Tobin and the team of scientists discovered that very young disks can have similar sizes, but are, in general, much more gigantic than older disks.

Protostars, which are very young stars, take shape in clouds of dust and gas. [Image: ALMA (ESO/NAOJ/NRAO), J. Tobin; NRAO/AUI/NSF, S. Dagnello; Herschel/ESA]
“When a star grows, it eats away more and more material from the disk. This means that younger disks have a lot more raw material from which planets could form. Possibly bigger planets already start to form around very young stars,” he explained.

Amid countless survey captures, four protostars seemed different when compared to the rest, and caught the team’s attention.

“These newborn stars looked very irregular and blobby,” said team member Nicole Karnath of the University of Toledo, Ohio (now at SOFIA Science Center). “We think that they are in one of the earliest stages of star formation, and some may not even have formed into protostars yet.”

The excellent resolution and accuracy offered by both instruments were vital to learning about both the outer and inner areas of protostars and their disks in this research. The ALMA is able to observe the dense material surrounding the young stars in accurate detail, and the images provided by VLA captured at longer wavelengths were crucial to see the inner structures of the youngest protostars at levels smaller than our Solar System.

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