Rapid-forming giants could disrupt spiral protoplanetary discs

Rapid-forming giants could disrupt spiral protoplanetary discs
Protoplanetary disc with an orbiting planet. Credit: University of Warwick

Giant planets that developed early in a star system’s life could solve a mystery of why spiral structures are not observed in young protoplanetary discs, according to a new study by University of Warwick astronomers.


The research, published today in the Astrophysical Journal Letters andpart supported by the Royal Society, provides an explanation for the lack of spiral structure that astronomers expect to see in protoplanetary discs around young stars that also suggests that scientists may have to reassess how quickly planets form in a disc’s lifecycle.

Protoplanetary discs are the birthplaces of planets, harbouring the material that will eventually coalesce into the array of planets that we see in the Universe. When these discs are young they form spiral structures, with all their dust and material dragged into dense arms by the massive gravitational effect of the disc spinning. A similar effect occurs at the galactic level, hence why we see spiral galaxies such as our own, the Milky Way.

Over the course of three to ten million years material from the disc comes together to form planets, falls onto the star it is orbiting or just disperses into space through winds coming off the disc. When a disc is young it is self-gravitating, and the material within it forms a spiral structure which it loses when it becomes gravitationally stable. Young planets that develop then carve out gaps in the disc as they consume and disperse material in their way, resulting in the ‘ring and gap’ features that astronomers most commonly see in protoplanetary discs.

Video showing a protoplanetary disc’s evolution with an orbiting 3 Jupiter mass planet. Credit: University of Warwick

But astronomers have struggled to account for observations of young protoplanetary discs that show no signs of spirals, but instead look like a disc much older with a ring and gap structure. To provide an explanation, Sahl Rowther and Dr. Farzana Meru from the University of Warwick Department of Physics conducted computer simulations of massive planets in young discs to determine what would happen when they interacted.

They found that a giant planet, around three times the mass of Jupiter, migrating from the outer regions of the disc towards its star would cause enough disruption to wipe out the disc’s spiral structure with results much like the discs observed by astronomers. However, to be present in the spiral stage of the disc those planets would have to form rapidly and early in the disc’s lifecycle.

Lead author Sahl Rowther, Ph.D. student in the Department of Physics, said: “When discs are young, we expect them to be massive with spiral structures. But we don’t see that in observations.

“Our simulations suggest that a massive planet in one of these young discs can actually shorten the time spent in the self-gravitating spiral phase to one that looks more like some of the observations that astronomers are seeing.

Video showing the protoplanetary disc’s evolution without a planet. Credit: University
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Want To Disrupt An Industry? Solve A Problem For Someone You Know

A lot of entrepreneurs talk about “disrupting their industry.” They want their idea to smash into the landscape like an asteroid, sending up a smoke cloud the whole world will see. We’ve seen all sorts of mega disruptions in recent years: Netflix, the iPhone, Prime 2-day shipping.

The only problem with this idea is that disrupting an industry is difficult. Really difficult. It’s akin to setting out to find your soulmate. Sure, it can happen, but is setting such a lofty goal upfront the right way to go? Or should you reframe your approach to improve your odds of success?

Dr. John Jaquish, author of the new book Weightlifting Is a Waste of Time, advocates for the latter. If you want to disrupt an industry, don’t start with that goal in mind. Instead, look to solve a problem for someone you know. Look back at that list of disruptions I mentioned above and you can clearly see the problem that each of them were trying to solve. That’s what allowed those ideas to become ground-shaking revelations—it was a side effect, not the original aim.

In his book, Dr. Jaquish tells a great story about where to find problems you can solve. You see, he’s the creator of the X3 exercise system, which is upending the fitness world. But that’s not where he started on this journey. He started with a simpler goal: to help his mom.

Starting Small to Go Big

When Dr. Jaquish’s mother was diagnosed with osteoporosis, she had a tough decision to make: take the pharmaceuticals and hope to avoid the laundry list of unpleasant side effects, or forgo the drugs and hope to never fracture a bone. She was dead set: no drugs for her.

With an avid interest in human physiology and a father who held over 300 patents in his lifetime, Dr. Jaquish set out to create a device that could help strengthen his mother’s bones. He found inspiration in the unlikeliest of places: gymnasts, who, despite their small stature, have strong bones due to the infrequent impact of their movements and routines. Dr. Jaquish knew his mother wasn’t going to take up competitive gymnastics, but it offered a way forward.

Over the next few years, Dr. Jaquish iterated through several different design concepts for a device that would help his mother. Finally, the commercial version of OsteoStrong’s Spectrum System was unveiled. The device has been a huge success in more ways than one.

Dr. Jaquish’s mother no longer has osteoporosis, and his device has since been placed in over 300 clinics worldwide, helping over 600,000 individuals with their bone health.

Transitioning to a Wider Audience

Had Dr. Jaquish started out trying to reverse the effects of osteoporosis for all women, he might never have gotten his device off the ground. Not only for the money, effort and coordination required to reach such a wide audience,

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