How long do most planets last?

abdulmanannet77@gmail.comFebruary 15, 2026

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Planets go through different stages of their lives: they form, evolve and eventually end. But the timelines of these processes differ significantly between Earth-like planets and worlds orbiting less powerful stars.

So how long do most planets last?

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(Image credit: Marilyn Perkins / Future)

“Planets start as microscopic dust grains in disks orbiting young stars, and eventually grow enormously following a series of collisions.” Sean Raymondastrophysicist at the University of Bordeaux in France, told Live Science in an email.

Gas giants, like Jupiter and Saturn, start out as huge, rocky, icy cores, then capture gas from the disk to become giants. Rocky planets like Earth experience a late phase of giant collisions with other growing planets and smaller objects after the sun’s gas disk dissipates, Raymond said. However, there still remains a debate among scientists about the order in which the planets formed.

Defining the “end” of a planet, however, is more complicated. “You could say that a planet lasts until it is destroyed” Matthew Reinholda planetary scientist at Stanford University, told Live Science. Or, you could define the end of a planet as the point at which it no longer functions under the same conditions. “You could say, ‘It was a world that had these conditions at one point, but now it’s changed and has these very different conditions,'” Reinhold said. “Because I prefer these previous conditions; I consider this planet to be finished.'”

Let’s take Earth as an example. Like many others, the lifespan of our planet is linked to the evolution of the sun. The sun currently creates heat and light through nuclear fusion at its heart – a process in which hydrogen is transformed into helium. In approximately 5 billion yearsthe Sun will run out of hydrogen, at which point it will expand into a red giant and eventually collapse in on itself.

An illustration of Proxima b, the closest star to our system, as a glowing ball of light, with a small planet silhouetted in the foreground.

An illustration of Proxima b, a pale red dwarf that is the closest star to the sun. Planets orbiting red dwarf stars tend to be long-lived. (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)

“Our Earth is going to ‘die’ in many ways,” Raymond said. “First, the slowly brightening Sun will make conditions on Earth unlivable by vaporizing the oceans. Second, Earth could be swallowed up by the Sun when it becomes a red giant. Finally, Earth (if still there) will be thrown into interstellar space.”

According to these calculations, the Earth total lifespan will be around 9.5 billion years.

Earth probably won’t live as long as most planets, he noted. This is because, unlike sunwho is a yellow dwarf star, Most stars are red dwarfs, smaller and cooler than our sun, and they burn fuel much more slowly. “They can last for billions of years,” Reinhold said.

In this case, it might not be the death of the star, but rather an internal process leading to the disappearance of these planets.

In his work, Reinhold modeled what could happen to a hypothetical habitable planet orbiting a red dwarf star. Active geology, such as plate tectonics, East considered crucial for habitability because it allows nutrients to move between the mantle and the planet’s surface and drives the carbon-silicate cycle.

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

Reinhold found that mantle convection would last between 30 and 90 billion years, while mantle melting could last between 16 and 23 billion years. Although these number ranges are too large to be meaningful, Reinhold said, they suggest that any Earth-like planets orbiting a red dwarf will die from an internal process long before their stars approach the end of their lives. And even in the shortest timescales, most rocky planets orbiting red dwarfs will maintain their conditions for billions of years.

Larger stars have much shorter lifespans because they use up their nuclear fuel more quickly. So the fate of an inner planet orbiting a white Type A star, for example, would be linked to the star’s lifespan, between 100 million and 1 billion years.

It’s also possible that gas giants lose their atmospheres due to their star’s intense light, Reinhold said, becoming rocky planets. This process depends on the distance between a planet and its star, the amount of energetic radiation emitted by the star, and the strength of a planet’s gravity. “The stronger their gravity, the better they retain their atmosphere, and the more radiation they receive from their star, the more intense the stripping power,” Reinhold explained. Depending on these factors, it could take anywhere from millions to billions of years.

The end of the universe

Even when a planet’s conditions change over time, the rock itself still exists. But over long timescales, there are different possibilities for its fate, as the probability of rare events increases. It could collide with another planet or be knocked out of its orbit.

“In all this chaos over quadrillions of years, planets that have been pushed away from their stars will be kicked out of the galaxy to wander for eternity in the void,” Reinhold said. “What really seals [its] fate really depends on the nature of the end of the universe,” Reinhold said.