Just before our sun dies, its light will shatter the asteroid belt into dust


The light from a dying star is so intense that it can reduce asteroids to dust. A new study says this will happen to most of the stars currently burning in the Universe, including the Sun, which will shatter its asteroid belt into boulders in about 5 to 6 billion years.

The only agent of this mass destruction is electromagnetic radiation, according to the modeling, and it is linked to the Yarkovsky-O’Keefe-Radzievskii-Paddack effect (YORP), named after the four scientists who contributed to its understanding.

The YORP effect occurs when heat from a star changes the rotation of a small object in the solar system – an asteroid, for example.

Light energy from the Sun is absorbed by the asteroid, heating it up. The heat works its way through the rock until it is again emitted in different directions in the form of thermal radiation.

This emission generates a tiny amount of thrust; over short periods of time it doesn’t really change much, but over longer periods it can spin or wobble an asteroid off-axis.

The asteroid tumbling phenomenon is one way we can already observe this process today. But as the Sun evolves, the effect will become more pronounced.

When main sequence stars like the Sun reach their advanced age stage, they enter what is called the giant branch stage as they expand, becoming very large and very bright. . This stage only lasted a few million years ago – whoosh! – they eject their outer material and collapse into a dense dead star called a white dwarf.

For the Sun, this process will take place in about 5 or 6 billion years (mark it in your calendar).

“When a typical star reaches the giant branch stage, its luminosity peaks between 1,000 and 10,000 times the luminosity of our Sun,” explained astrophysicist Dimitri Veras of the University of Warwick.

“Then the star contracts very quickly into an Earth-sized white dwarf, where its luminosity drops to levels below that of our Sun. Therefore, the YORP effect is very strong during the branch phase. giant, but almost non-existent after the star became a white dwarf. “

Due to the initially increased brightness, the YORP effect would also increase. And most asteroids are not dense boulders; rather, they are low density, cavity-riddled conglomerates known as “rubble heaps”.

According to the team’s computer modeling, the YORP effect would spin most asteroids over 200 meters in diameter (around 660 feet) enough to fracture and disintegrate.

This decay wouldn’t happen to objects with higher structural integrity, like dwarf planets (so Pluto is safe!). But an asteroid belt has a different fate.

“For a branch of giant solar-mass stars – like what our Sun will become – even the analogues of the exo-asteroid belt will effectively be destroyed,” Veras said.

“The YORP effect in these systems is very violent and acting 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 only because of the light of our Sun. “

It is not only computer modeling that shows the proof. Our observations of white dwarfs also suggest this.

More than a quarter of white dwarf stars have evidence of metals from asteroid innards in their spectra. These asteroid signatures in the spectra of white dwarfs are a mystery and are still the subject of debate.

The YORP effect could explain how the asteroid metals got there. As the asteroids collapse, they form a disk of asteroid dust around the white dwarf, part of which rushes into the dead star.

“These results help locate debris fields in giant branched and white dwarf planetary systems, which is crucial in determining how white dwarfs are polluted,” Veras said.

“We need to know where the debris is when the star becomes a white dwarf to understand how the disks form. So the YORP effect provides important context to determine where this debris would come from.”

The research was published in the Monthly notices from the Royal Astronomical Society.

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