Jupiter, the largest planet in our solar system, has a volume 1300 times that of our Earth and a mass 318 times that of Earth. In both aspects, Jupiter is undoubtedly the “King of Planets” in our solar system.
However, planets are actually a common type of celestial body in the universe, and there are many such celestial bodies in the Milky Way. Astronomers believe that there are 100-400 billion stars in the Milky Way, but the number of planets is probably several times more. In the face of such a large population, there must be larger planets than Jupiter. Recently, media reports have reported that a team of astronomers led by the Institute of Astronomy at the University of Hawaii (UH IFA) has discovered a giant planet near a distant star, with a mass three times that of Jupiter, or equivalent to the mass of 1000 Earths. The planet has been named Kepler-88d. Through years of observation, it has been found that the planet orbits its main star every four years, but its orbit is not circular, but elliptical. In this planetary system, there is also Kepler-88c, which has a mass almost the same as Jupiter, while Kepler-88b has a mass similar to Uranus, equivalent to the mass of over 10 Earths. Compared to Earth, these two “brothers” are also very big.
Kepler-88d has a mass three times that of Jupiter, so it is the largest planet and can be called the “King of Planets”, right? Actually not, it can be said that it is still far behind! According to existing theories of planet formation and classification, the maximum mass of a planet can reach 13 times that of Jupiter. If this limit is exceeded, the planet may trigger internal deuterium fusion, becoming a brown dwarf. If the mass reaches 80 times that of Jupiter, the star will trigger internal hydrogen fusion, becoming a star. Judging by this perception, the mass of the largest planet can reach 13 times that of Jupiter, so a planet with a mass three times that of Jupiter cannot be called the “King of Planets”. However, the duration of deuterium fusion inside a brown dwarf star is not long, usually not exceeding 100 million years. After the deuterium fusion inside the star is completed, this type of star looks no different from other planets. Therefore, many astronomers and astronomical institutions classify brown dwarfs as planets. If classified according to this understanding, the maximum mass of planets can reach 80 times that of Jupiter, Only planets with a mass 80 times that of Jupiter can be called the “King of Planets”. Is there such a planet in the universe? Of course there is! For example, Kepler 39b, with a mass 18 times that of Jupiter, and Gliese 229b, with a mass more than 50 times that of Jupiter. If brown dwarfs are also considered planets, their mass is undoubtedly quite astonishing. Of course, there are even larger brown dwarfs, but due to their extremely weak and even non luminous light, it is difficult to observe them.
So what is the maximum size of a planet with a known mass below that of a brown dwarf? Astronomers have observed planets with a mass of about 13 times that of Jupiter, such as Andromeda Caba b, which has a mass of about 13 times that of Jupiter, but it is still uncertain whether it is a planet or a brown dwarf.
It is worth mentioning that HD 100546b, located 320 light-years away from Earth, is considered the largest planet in terms of volume. Its diameter is about 65% of that of the Sun, and its volume is equivalent to 1/4 of that of the Sun. It is the size of 250 Jupiter and can hold over 300000 Earths. In terms of volume, it is known as the “King of Planets”.