Although the character of Peter Pan may be fictional, if you look to the “second star to the right, and [go] straight on ‘til morning,” you may well find a real cosmic wonder that “never grows up”.
So-called Peter Pan disks are giant planet-forming (protoplanetary) disks of gas and dust that encircle young low-mass stars. What sparked their nickname, however, was their ability to live around 5-10 times longer than typical protoplanetary disks. First discovered in 2016, there is still much to learn about this unique class of disk, including the reason for its seemingly never-ending youth.
To address some of these questions, a pair of researchers from Queen Mary University of London used computer simulations to figure out the conditions of a “Neverland” that would lead to the formation of such disks. Their results, published in the Monthly Notices of the Royal Astronomical Society: Letters, suggest that unlike the character Peter Pan, his celestial counterparts do not have their own bands of “lost boys.”
“Most stars form in big groups containing around 100,000 stars however it seems that Peter Pan disks can't form in these environments,” Dr Gavin Coleman, first author of the study and postdoctoral researcher at Queen Mary, said in a statement. “They need to be much more isolated from their stellar neighbors as the radiation from other stars would blow these disks away. They also need to start out massive, so they have more gas to lose and are therefore able to live for much longer.”
Whilst most planet-forming disks fade away after a few million years having “quickly” sprouted planets, Peter Pan disks exceeding this age still appear to be in the midst of this process. The recent observations of only a handful of such disks hooked researchers into deciphering their never-before-seen characteristics.
“The existence of these long-lived disks was really surprising, and finding out why these disks can survive longer than expected could be critical for helping us understand more about disk evolution and planet formation in general,” said co-author Dr Thomas Haworth also from Queen Mary.
“A particularly interesting point is that Peter Pan disks 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 disk masses that we need to end up with Peter Pan disks could be an important ingredient that allows these planets to exist.”
Seven of these rare disks were discovered as part of a citizen science project called Disk Detective, a collaboration between NASA and Zooniverse. In fact, the same platform recently identified the closest brown dwarf to Earth with a disk younger than 5 million years old. A revamped version has just been launched with the hope that more Peter Pan disks can be unearthed.
“It's great that the findings of a citizen science project are now fueling novel scientific research into these unique disks, and could even help us to better understand planet formation, one of the key problems in astrophysics,” Coleman said.