Further Secrets of Planet Creation Uncovered

Artist’s concept of a Peter Pan disk. (Photo courtesy of Jonathan Holden/NASA).

(CN) — British scientists have revealed how the recently discovered planet forming disks, coined with the name Peter Pan disks for their longevity, come to be formed, furthering our understanding of how planets are created.

Protoplanetary disks are massive planet-forming disks of gas and dust that are found circling protostars following the collapse of a molecular cloud. The materials expelled from this collapse begin to rotate and move inwards towards the protostar resulting in the characteristic disk shape.

In a study published Wednesday in the Monthly Notices of the Royal Astronomical Society, scientists from Queen Mary University of London conducted a series of computer simulations to investigate how these disks evolve over time.

The simulations took various starting configurations in which the disks would begin to reveal what they called “Neverland’s parameters,” which are the conditions needed for a Peter Pan disk to form. The findings showed that they need significantly more space to form than normal disks, resulting in them forming far away from other stars in more secluded environments.

In 2016 a NASA project yielded the discovery of the oldest known disk to date. The citizen scientists responsible for the find settled on the name Peter Pan disks because, much like the beloved fictional character, these formations “never grow up” and can live 5-10 times longer than the average protoplanetary disk.

Since the discovery, however, these Peter Pan disks remain a mystery in many ways, as astronomers have been searching for answers about how they allow planets to form and why they are able to live for so long.

“Most stars form in big groups containing around 100,000 stars, however it seems that Peter Pan discs can’t form in these environments. They need to be much more isolated from their stellar neighbours as the radiation from other stars would blow these discs away,” Gavin Coleman, first author of the study and postdoctoral researcher at Queen Mary. “They also need to start out massive, so they have more gas to lose and are therefore able to live for much longer.”

It was previously believed that all disks have a life expectancy of a few million years, now disproved by the existence of Peter Pan disks. They were said to dissipate within 10 million years at most, which in turn led scientists to believe that the planets within them have a relatively small window to form completely. The emergence of this new evidence reveals that Peter Pan disks can live up to ten times longer in planet formation.

“The existence of these long-lived discs was really surprising, and finding out why these discs can survive longer than expected could be critical for helping us understand more about disc evolution and planet formation in general,” Thomas Haworth, a Dorothy Hodgkin Fellow at Queen Mary.

Additionally, these gas-rich disks have only been discovered so far around stars with lower masses, leading scientists to conclude that the disks around M-dwarfs take much longer to dissipate than around high-mass stars. It also suggests that around these stars, planets take much longer to form than previously thought.

“A particularly interesting point is that Peter Pan discs have so far only been found around low mass stars, and these low mass stars are generally being found to host lots of planets,” Haworth continued. “The large disc masses that we need to end up with Peter Pan discs could be an important ingredient that allows these planets to exist.”

The results of this study suggest that these Peter Pan disks are a rare occurrence due to their specific requirements for formation. Furthermore, seven of these disks have been discovered thus far, indicating that this isn’t just an outlying event but rather a new class of disks.

These disks have all been discovered due to the efforts of a research endeavor called the Disk Detective Project, led by citizen scientists in collaboration with NASA and Zooniverse. Moving forward, the next step for this study will be to characterize the known Peter Pan disks and search for more.

The authors have been granted use of the Chandra X-Ray Observatory to observe X-ray fluxes, which will allow them to see how quickly the star’s energy will evaporate the surrounding disk material. They will also be following up with the Magellan Telescope in Chile this coming June.

“It’s great that the findings of a citizen science project are now fueling novel scientific research into these unique discs, and could even help us to better understand planet formation, one of the key problems in astrophysics,” said Coleman.

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