How big can the planets in the universe be? Is there a limit to how big a planet can grow, or are there colossal worlds that dwarf even our own sun?
To answer this question, we need to understand what a planet is and how it forms. A planet is a celestial body that orbits a star and has enough mass to be spherical and clear its environment of other objects.
Planets form from the leftover material from a star’s birth, called the protoplanetary disk. This disk is made of gas and dust that clump together under the influence of gravity and eventually become large enough to be considered planets.
However, not all planets are the same. There are two main types of planets: rocky and gaseous. Rocky planets are usually made of solid materials, such as iron, silicon, carbon and oxygen.
They are usually smaller and denser than gaseous planets, which are mostly composed of hydrogen and helium. Gaseous planets are also called gas giants or Jovian planets, after Jupiter, the largest planet in our solar system.
The size of a planet depends on several factors, such as its mass, density, composition, temperature and distance from the star. Mass is the amount of matter in an object, while density is the ratio of mass to volume.
Composition is the type and ratio of the elements that make up a planet. Temperature is the measure of how hot or cold a planet is, which affects how much it expands or contracts. The distance from the star determines how much heat and radiation a planet receives, which also affects its size.
In general, rocky planets have a smaller range of sizes than gaseous planets. The largest rocky planets, called super-Earths, are about twice as wide as Earth. For example, Kepler-10c is a super-Earth with a radius about 2.3 times that of Earth and a mass about 17 times that of Earth.
However, rocky planets can’t get much bigger than that because they would start to collect gas, ice and water, gradually turning into gaseous planets with a rocky core.
Gaseous planets have a much wider range of sizes than rocky planets. The smallest gaseous planets, called mini-Neptunes or sub-Neptunes, are about four times as wide as Earth. For example, Kepler-138d is a mini-Neptune with a radius about 4.1 times that of Earth and a mass about 1.5 times that of Earth.
The largest gaseous planets, called super-Jupiters or ultra-Jupiters, are about twice as wide as Jupiter. For example, HAT-P-67 b is a super-Jupiter with a radius of about 2 times that of Jupiter and a mass of only about 0.34 times that of Jupiter.
However, gaseous planets also have a limit to how big they can get. As they grow in mass, they also become denser and more compact, making them smaller. The most massive planets are about 13 times as massive as Jupiter. Beyond that point they would become brown dwarfs, failed stars too small to ignite nuclear fusion in their cores.
So, what is the largest planet in the universe? Based on current observations and theoretical modelsThe largest planet in terms of width will likely be about twice as wide as Jupiter, while the largest planet in terms of mass will likely be about 13 times as massive as Jupiter. However, these numbers are not definitive, as new discoveries in the future may reveal even larger or more massive planets.