How long do most planets last?

Planets go through various life stages, forming, evolving, and eventually coming to an end. But the timeline of these processes is very different for Earth-like planets and worlds orbiting less powerful stars.

So how long do most planets last?

First, it’s important to understand the life cycle of a planet.

you may like

“Planets start out as tiny dust particles in a disk orbiting a young star, and eventually grow into enormous sizes through a series of collisions,” Sean Raymond, an astrophysicist at the University of Bordeaux in France, told Live Science via email.

Gas giant planets like Jupiter and Saturn start out as huge rocky or icy cores, then take in gas from their disks and become giants. Raymond said rocky planets like Earth undergo the late stages of giant collisions with other growing planets or small bodies after the disk of gas from the Sun disappears. However, there is still debate among scientists about the order in which planets formed.

However, defining the “end” of a planet is more complicated. “You could say that planets survive until they’re destroyed,” Matthew Reinhold, a planetary scientist at Stanford University, told Live Science. Alternatively, the end of a planet can be defined as when it no longer operates under the same conditions. “You can say, ‘This is how the world was at one point in time, and now it’s changed and it’s a completely different situation,'” Reinhold said. “Because I prefer the way it was and think this planet is over.”

Let’s take the Earth as an example. Like many other planets, the lifespan of our planet is related to the evolution of the Sun. The sun currently produces heat and light through nuclear fusion at its core, a process in which hydrogen turns into helium. In about 5 billion years, the Sun will run out of hydrogen, at which point it will expand into a red giant star and eventually collapse.

“Our planet will ‘die’ in different ways,” Raymond said. “First, a slowly brightening sun would evaporate the oceans and make conditions on Earth uninhabitable. Second, Earth might become a red giant and be swallowed by the sun. Finally, Earth (if it still exists) would be catapulted into interstellar space.”

According to these calculations, the total lifespan of the Earth is approximately 9.5 billion years.

Earth probably won’t survive as long as most planets, he noted. That’s because unlike the Sun, which is a yellow dwarf, most stars are red dwarfs, which are smaller and cooler than the Sun and burn fuel much more slowly. “They can last trillions of years,” Reinhold said.

you may like

In that case, it may not be the death of the star, but rather an internal process that leads to the demise of these planets.

In his research, Reinhold modeled what would happen to a hypothetical habitable planet orbiting a red dwarf star. Active geology, such as plate tectonics, is thought to be important for habitability because it enables the movement of nutrients between the planet’s mantle and surface, facilitating the carbon-silicate cycle.

“We want a planet that can stabilize its climate,” Reinhold said, noting that the carbon-silicate cycle is Earth’s natural thermostat.

Reinhold found that mantle convection lasts between 30 billion and 90 billion years, while mantle melt can last between 16 and 23 billion years. Although these numerical ranges are too large to be meaningful, they suggest that Earth-like planets orbiting red dwarf stars die from internal processes long before the star approaches the end of its life, Reinhold said. And even in the shortest timeline, most rocky planets orbiting red dwarfs remain that way for billions of years.

Large stars use up their nuclear fuel more quickly, so they have a much shorter lifespan. So, for example, the fate of inner planets orbiting A-type white stars will depend on the star’s lifespan of 100 million to 1 billion years.

Reinhold said it’s also possible that gas giants could lose their atmospheres due to the intense light from their stars and become rocky planets. This process depends on how close a planet is to its star, how much energy radiation the star emits, and how strong the planet’s gravity is. “The stronger the gravity, the greater the ability to hold on to the atmosphere, and the more radiation it receives from the star, the stronger the exfoliation forces,” Reinhold explained. Depending on these factors, this can take millions to billions of years.

end of the universe

Even though the planet’s conditions change over time, the rocks themselves still exist. However, over long timescales, the probability of rare events increases, so there are many possibilities for its fate. It could collide with another planet or be ejected from orbit.

“During this quadrillion-year turmoil, planets that are ejected from their stars will be ejected from the galaxy and will forever wander in the void,” Reinhold said. “What is actually sealed is [its] “The fate really depends on the nature of the end of the universe,” Reinhold said.

Solar System Quiz: How much do you know about our cosmic neighborhood?