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Can a Planet Become a Star?

Jupiter, our solar system’s largest planet, is 318 times the size of Earth. The planet is mainly made up of gas and has a magnetic field fourteen times that of Earth. Jupiter is often referred to as the “failed star” due to its high hydrogen content, between 88-92%. So could Jupiter potentially turn into a star someday? Can a planet become a star? 

A planet can’t become a star. That is unless you classify brown dwarfs as planets. Technically, brown dwarfs are neither a planet nor a star, and will never become a star due to lack of fusion. While brown dwarfs are sometimes called “hot planets,” they are born much like a star. 

Confused? Planets don’t have the mass, (even hefty Jupiter), to become stars. Brown dwarfs, however, have much more mass than planets, but not enough to ignite. Thus, while they are incredibly hot, they don’t make new heat as stars do, like our Sun. The key is found at the beginning when planets and stars are born. So let’s back up and work our way through this…

How a Planet is Formed

Scientists agree that planets begin as a disk of gas and dust that swirls around a newborn star. Eventually, this swirling disk becomes a planet. But the process between being a swirling disk, known as an accretion disk, and turning it into a planet has been a debated mystery.

Because to make a planet, there needs to be a certain number of collisions happening in the accretion disk. But if they are the wrong collisions, then dust and debris would scatter rather than grow into a swirling ball. So there need to be drag to bring these particles together. 

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But this still didn’t explain how everything stuck together. This led to the theory of “dust traps.” These traps slow things down and bring the dust inward and the gas out into a ring. This allows the particles to clump together and grow.

Check out my article “How Planets are Formed” for a detailed explanation about planet formation, and which planets resemble Earth the most!

How a Star is Formed

To understand how a star is born, we go back to dust. This dust is found in a cloud called a nebula that also contains hydrogen, helium, and other ionized gases. The cloud builds up mass, and some areas create so much mass its gravitational attraction causes it to collapse. The process of collapsing makes the center of all this get hot. Really hot.

This hot core starts gathering more dust and gas as it rotates. Some of this will swirl into a disk around the core, potentially becoming planets. Meanwhile, the core continues to heat up, and when it reaches 2,000 degrees, Kelvin hydrogen molecules start breaking apart into atoms. The temperature continues to increase and when it hits 10,000 Kelvin, fusion begins. 

For a more detailed explanation about the star formation, check out my article “How Stars are Formed: A Detailed Explanation” or “What Are Stars: Everything you Need to Know

How a Brown Dwarf is Formed

Brown dwarfs begin just like a star. They gather up hydrogen gas and gain mass, lots of mass. Brown dwarfs gather so much mass that despite them often being the same size as Jupiter, they’ll have somewhere between 10 and 90 times more mass than the planet. As big as that is, however, it isn’t enough to become a star.

A brown dwarf at its largest will only have half as much mass as our Sun. This lack of mass prevents the brown dwarf from igniting, starting the process of fusion. They get hot, but not hot enough. There is a weak, unique fusion that might occur, but it is temporary and different from a star’s fusion. Thus, the light and heat dwarf stars give off isn’t created energy, but what is left after being created. 

Check out our article, “The 5 Real Reasons Why Stars Have Different Colors

Brown Dwarfs and Dark Matter

The first brown dwarf was discovered in 1995. Thus, the research into them is pretty new and constantly evolving. The weak light and heat these not-stars give off also make them difficult to detect. However, these peculiar, difficult to classify oddities do interesting things. For example, scientists are finding superheated steam in the spectra of brown dwarfs. This is something you won’t find with stars.

As scientists began to look closer at brown dwarfs, they wondered if they were a link to dark matter, as the earlier video suggested. However, that didn’t seem to be the case. For starters, back in 2009, there didn’t seem to be enough of them. Also, what scientists found near them were Weakly Interacting Massive Partials that cannot be seen, like dark matter. But it isn’t dark matter, exactly.

But in 2017, a study came out claiming that there might be as many failed stars as stars. They still don’t know if brown dwarfs have anything to do with dark matter, per se. But scientists are now looking into if these brown dwarfs can help them better locate dark matter. 


While science is always learning more, it is highly unlikely a planet could ever become a star. This is because they are formed differently than stars. Brown dwarfs are the closest “thing” that could potentially become a star, but these not-planets-not-stars seem to continue to cool off rather than grow. That doesn’t make these failed stars boring, however. On the contrary, they might even be vital to locating more dark matter.

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