Starlight Could Break Up Asteroids

Electromagnetic radiation emitted from stars as they collapse might provide enough power to destroy asteroids, a research team believes.

A new study out of the University of Warwick’s Department of Physics, published in Monthly Notices of the Royal Astronomical Society, details how scientists analyzed the number of successive asteroid breakup events. Electromagnetic radiation emitted from stars just before they collapse into white dwarfs is believed to be strong enough to spin distant asteroids at high speed until they tear themselves apart.

The authors of the study concluded that all asteroids, saving the smallest and most distant, would be disintegrated in one million years.

Stars such as the sun have a phase during the end of their lifespan known as a giant branch, where all of their hydrogen fuel has been burned and their luminosity increases by a magnitude of 1000 to 10,000. The lead author of the study, Dimitri Veras, noted that after this, the star would then contract down to an Earth-size white dwarf, where its luminosity drops below the level of the sun. The radiation created from this is absorbed by orbiting asteroids where the energy is emitted at new locations in the orbit. This is known as the YORP effect, named after Yarkovsky, O’Keefe, Radzievskii, and Paddack, the scientists who contributed to the concept.

“Hence, the YORP effect is very important during the giant branch phase,” Veras said, “but almost nonexistent after the star has become a white dwarf. For one solar-mass giant branch stars, like what our sun will become, even exo-asteroid belt analogs will be effectively destroyed. The YORP effect in these systems is very violent and acts quickly, on the order of a million years. Not only will our own asteroid belt be destroyed, but it will be done quickly and violently. And due solely to the light from our sun.”

Veras said the asteroids will eventually form a disc of debris around the white dwarf. The pollution created by this disc is used by astronomers to determine its composition.

“These results help locate debris fields in giant branch and white dwarf planetary systems, which is crucial to determining how white dwarfs are polluted,” Veras said. “We need to know where the debris is by the time the star becomes a white dwarf to understand how discs are formed.”

The current estimate for the remaining lifespan of the sun is 6 billion years, at which time its hydrogen is expected to run out and it will become a white dwarf. As its luminosity grows it will bombard the asteroid belt with radiation, breaking the asteroids into smaller pieces. These smaller pieces are said to have greater internal strength. Once the giant branch phase starts, the process will continue unabated until reaching a plateau of asteroids with diameters of 1-100 meters. Researchers believe the YORP effect will influence only asteroids, with objects larger than Pluto likely escaping this fate.