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Supercharged light pulverizes asteroids

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Christian Fernsby ▼ | February 12, 2020
The majority of stars in the universe will become luminous enough to blast surrounding asteroids into successively smaller fragments using their light alone, according to a University of Warwick astronomer.
Asteroid
In space   Asteroid
Electromagnetic radiation from stars at the end of their 'giant branch' phase lasting just a few million years before they collapse into white dwarfs would be strong enough to spin even distant asteroids at high speed until they tear themselves apart again and again.

As a result, even our own asteroid belt will be easily pulverized by our Sun billions of years from now.

The new study from the University of Warwick's Department of Physics, published in Monthly Notices of the Royal Astronomical Society, analyses the number of successive break-up events and how quickly this cascade occurs.

The authors have concluded that all but the most distant or smallest asteroids in a system would be disintegrated in a relatively short one million years, leaving behind debris that scientists can find and analyse around dead white dwarf stars.

Some of this debris may be in the form of 'double asteroids' which revolve around each other while they orbit the Sun.

After main sequence stars like our Sun have burnt all their hydrogen fuel, they then become hundreds of times larger during a 'giant branch' phase and increase their luminosity ten thousand fold, giving out intense electromagnetic radiation.

When that expansion stops, a star sheds its outer layers, leaving behind a dense core known as a white dwarf.

The radiation from the star will be absorbed by orbiting asteroids, redistributed internally and then emitted from a different location, creating an imbalance.

This imbalance creates a torque effect that very gradually spins up the asteroid, eventually to break up speed at one full rotation every 2 hours.

This effect is known as the YORP effect, named after four scientists Yarkovsky, O'Keefe, Radzievskii, Paddack who contributed ideas to the concept.

Eventually, this torque will pull the asteroid apart into smaller pieces.

The process will then repeat itself in several stages, much like how in the classic arcade game 'Asteroids' they break down into smaller and smaller asteroids after each destruction event.

The scientists have calculated that in most cases there will be more than ten fission events or break ups before the pieces become too small to be affected.

Lead author Dr Dimitri Veras, from the University of Warwick's Astronomy and Astrophysics Group, said: "When a typical star reaches the giant branch stage, its luminosity reaches a maximum of between 1,000 and 10,000 times the luminosity of our Sun.

"Then the star contracts down into an Earth-sized white dwarf very quickly, where its luminosity drops to levels below our Sun's.

H"ence, the YORP effect is very important during the giant branch phase, but almost non existent after the star has become a white dwarf."


 

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