The birth or death of a planetary system is never anything less than spectacular – and, thanks to the marvels of modern astronomy, we can witness distant worlds and planetesimals begin and end around blazing stars in the deep, enigmatic dark. Often, the rotating debris disks of gas and dust whizzing around these spheres of light are beautiful, geometrically perfect circles.
Zoom in, though, and fine details begin to emerge, of remarkable arcs, strange indentations, and curious streaks; imperfections in the masterpieces taking shape. It’s previously been assumed that to create these idiosyncratic touches, you’d need a planet, whose gravity would alter the movement of the rings – but a new NASA study suggests something rather remarkable may also be happening.
According to simulations run on the Discover supercomputing cluster at NASA’s Goddard Space Flight Center, the intense light from high-energy stars can disrupt these distant disks, which etches stunning, ephemeral patterns into them. In order to understand how, we need to go back to 2013.
Back then, Wladimir Lyra, a professor of astronomy at California State University, Northridge, and Marc Kuchner, an astrophysicist at Goddard, teamed up to better understand why disks aren’t always perfectly formed. Publishing a new model in Nature, they explained that sharply defined rings and broken circles – or arcs – could form when stars emit enough ultraviolet light.
Ultraviolet light is incredibly energetic, so when it smashes into the gas, dust, and ice within these disks, it can strip away electrons from their individual particles. Although some may be ejected into deep space, others will cascade into other parts of the disk, which will trigger heating.
Heat the gas, and you amp up its pressure, causing it to expand. This attracts more dust, which often warms up nearby gas. Thanks to this so-called “photoelectric instability” (PeI) mechanism, a self-sustaining cycle begins, and strange shapes within the disk take shape.
Exoplanet hunters sometimes look for these weird clumps in an attempt to indirectly detect them, but the key finding of this 2013 study was that you don’t need planets to make these patterns.