The Sun’s fate is sealed. Humanity used to ask the stars about the future. For some time now, it is the other way around. We are the ones predicting the stars’ future. That’s astrology turned into astronomy.
So, the Sun will eventually die. It doesn’t have enough mass to explode as a supernova. It won’t disappear, but it will become something else: a white dwarf. A white dwarf is the remains of a former star that doesn’t have enough power left to shine. When that happens, the Sun System will change, too, entirely.
The Sun will melt the Asteroid Belt before it dies
It looks like the Sun will die by its own weapon (or blessing for that matter): light and heat. In about five to six billion years, the electromagnetic radiation of the Sun will get too high even for its endurance. It’s like a suicidal process. The luminosity will become 1000 to 10.000 times higher and, at some point, will collapse.
The process is called asymptotic-giant-branch. It is a late period in the lives of all low- to intermediate-mass stars, where they expand and become red giants. While it’s at it, the giant branch dramatically changes everything close to it, and also far from it.
Ejecting its outer material can reduce asteroids to dust. It is called the YORP effect. This is what will happen to the Asteroid Belt, as well, when the time comes for the Sun to die.
The YORP effect
YORP is an acronym coming from the names of the scientist that explain it. Yarkovsky–O’Keefe–Radzievskii–Paddack. It changes the rotation state of a small astronomical due to the scattering of solar radiation off its surface and the emission of its thermal radiation. Electromagnetic radiation interacts with the surface of an asteroid in three significant steps:
- First: radiation from the Sun is absorbed.
- Second: the surface of the body diffusively reflects radiation.
- Third: and the body’s internal energy is emitted as thermal radiation.
The creation of binary and tumbling asteroids, as well as the changes in an asteroid’s pole to the ecliptic plane, is due to the YORP effect.
The consequences of YORP and asymptotic-giant-branch
The heat of the Sun changes the orbit of the asteroids. The phenomenon can already be observed, asteroids changing their course due to the hieratic activity of the Sun.
But when the time comes for the Sun to move to its final stage as a star, and its radioactivity will be unbearable even for the Sun, the Asteroid Belt will turn to dust and ashes. Asteroids wider than 200 meters will fracture and disintegrate. Exo-asteroid belt analogs will be shattered to pieces.
After about 20 million years on the early asymptotic-giant-branch, the Sun will become increasingly unstable. It will rapidly lose mass, and the thermal pulses will increase the size and luminosity for a few hundred years every 100,000 years.