Credit: NASA
Astronomers have observed that most star systems usually fall into one of two categories: alive and dead. While there are many healthy yellow and red stars which are hosting planets, there are also dead white dwarf stars which are unlike future versions of our sun, many of which feature disks of dust, gas, and shattered debris. How does a dying star reduce the first system to the second? In part by pulverizing its asteroids with next-level sunlight, recent research suggests.
When the Sun in 5 to 6 billion years balloons into a red giant, swallowing Mercury and Venus whole and scorching Earth, this will be just its first step in transforming the solar system. Since the Sun will grow so much larger, it will flood space with thousands of times more light than it currently does, like swapping out a lamp for a searchlight.
One of the most dramatic effects of this increased energy abundance will be to spin asteroids into much smaller pieces, suggests a recent publication in the Monthly Notices of the Royal Astronomical Society. The phenomenon could explain why astronomers see so many mini-asteroids falling into white dwarf stars. "We need to know where the debris is by the time the star becomes a white dwarf to understand how discs are formed. So the YORP effect provides important context for determining where that debris would originate."
The root cause of this mass destruction is electromagnetic radiation, according to modelling, and it has much to do with the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, named after the four scientists who contributed to understanding how this process works. The YORP effect occurs when the heat of a star changes the rotation of a small Solar System object - an asteroid, for example. The YORP effect could explain how the asteroid metals got. As asteroids crumble, they form a disc of asteroid dust around the white dwarf, some of which gets slurped down into the dead star.
Asteroids: Crash Course Astronomy from CrashCourse on YouTube:
Light energy from the expanded Sun is then absorbed by the asteroid, warming it up considerably. The heat then makes its way through the rock until it is emitted again in different directions as thermal radiation. This emission additionally generates a tiny amount of thrust over short time periods, this doesn't really change much, but over longer periods, it can cause an asteroid to spin or wobble off-axis.
"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," explained astrophysicist Dimitri Veras of the University of Warwick.
The study of white dwarf stars as planetary systems is a fairly new field. When a sunlike star dies, it swells, expels a lot of its material, and eventually collapses, cramming a sun-like mass into an Earth-like space. That creates a powerful gravitational field that drags the star’s heavier elements into its center, leaving a pristine atmosphere of hydrogen with some helium. “I think of [white dwarves] as a blank sheet of paper,” says Mark Hollands, an astronomer at Warwick University.
The research has been published in the Monthly Notices of the Royal Astronomical Society.
Research paper:
https://academic.oup.com/mnras/article-abstract/492/2/2437/5682494?redirectedFrom=fulltext
References:
https://www.popsci.com/story/space/dying-stars-could-make-asteroids-explode/
https://www.sciencealert.com/just-before-our-sun-dies-its-light-will-pulverise-the-asteroid-belt
https://www.youtube.com/watch?v=auxpcdQimCs (above video)