The asteroid belt will disappear in 6 billion years

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We already know that the Sun will eventually expand and envelop the Earth, but for smaller and more distant objects, what will our star cause? It will be a deadly event, that’s for sure as the sun will literally make all of the asteroids die, so to speak.

A team of U.S. scientists claims that electromagnetic radiation from stars at the end of their giant asymptotic branch phase (a period of stellar evolution experienced by all intermediate-mass stars at the end of their lives) that lasts a few million years and in which they increase their luminosity 10,000 times before collapsing into white dwarfs, would be strong enough to tear apart asteroids. As a result, even the asteroid belt of our solar system will be pulverized by the Sun billions of years from now.

The new study, published in the Monthly Notices of the Royal Astronomical Society, analysed the number of successive rupture events and the speed with which this cascade of events occurs, concluding that, in about six billion years' time, when the Sun burns the last of its hydrogen reserves and becomes a red giant, it will eject very powerful streams of energetic particles into space that will be absorbed by the asteroids.

So, the star's radiation will be absorbed by the orbiting asteroids, redistributed internally and then emitted from a different location, creating an imbalance. This instability creates a torque effect that gradually rotates the asteroid. This is known as the YORP effect, named after four scientists (Yarkovsky, O'Keefe, Radzievskii, Paddack) who contributed ideas to the concept.

Gradually, the asteroids will break up into smaller and smaller pieces, as we have seen in other parts of our solar system; the process will repeat itself in several stages, rotating them faster and faster until, around one rotation every two hours, the internal stress tears the rocks apart and the asteroids break up into smaller and smaller objects (yes, like in the classic Atari arcade game "Asteroids") after each destruction event, until they eventually disappear.

"For a giant branch of the solar mass, like what our Sun will become, even the analogues in the exo-asteroid belt will be completely destroyed. The YORP effect on 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 happen quickly and violently. And only because of the light from our Sun", explains Dimitri Veras, from the Astronomy and Astrophysics Group at the University of Warwick, and leader of the study.

The remaining space dust from the pulverized asteroids will be dragged towards the star, already in the form of a white dwarf, like a disk of debris. It is clear that this would be an excellent time to study the pollution around this type of star, but it would be an impossible task since humans would have been extinct by then when our planet would have evaporated during the expansion of the Sun.

 

Reference: Dimitri Veras et al. Post-main-sequence debris from rotation-induced YORP break-up of small bodies - II. Multiple fissions, internal strengths, and binary production, Monthly Notices of the Royal Astronomical Society (2019). DOI: 10.1093/mnras/stz3565

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