Which is the largest planet in the universe?

Theoretically, the largest planet can only reach 70-80 times the mass of Jupiter. If the mass is greater, the planet will collapse into a star. But the largest planet actually observed is TrES 4 in Ursa Major, which is 1.7 times larger than Jupiter, but its mass is smaller than that of Mercury in the solar system.

For the universe we know at present, the largest planet is probably the planet numbered HD 106906 b. This planet, which is 300 light years away from the Earth, is considered to be nonexistent. Its mass is so great that scientists have even turned it into a failed star.

In the universe, planets in other galaxies can't be directly observed, because they don't emit light themselves, and the reflected star light can't be gathered to form an object image with a telescope after reaching the earth for a long distance. Even in the solar system, it used to be thought that there were only eight planets, dwarf planets such as birds, Pluto and some comets, but with the development of science and technology, scientists found that there seemed to be many massive celestial bodies in the solar system that had not been discovered. Although we can make some guesses through the laws of planetary motion, it is not easy to start with actual observation, and we don't know where to start.

In the solar system, when Jupiter and other large planets revolve around the sun, the sun will also "vibrate" because of gravity. In fact, the sun and Jupiter are actually moving in circles around the same point. Based on this phenomenon, we can judge whether there is a massive planet around the star by studying the running law of the star. In this way, scientists discovered many extraterrestrial planets and concluded that there is at least one planet around each star.

In the universe, many celestial bodies cannot be directly observed, and such indirect observation means are needed. For example, in the observation of black holes, because the mass of black holes is too large, it is difficult for light to escape and cannot be directly observed, but by observing the evolution and operation of surrounding stars, some indirect evidence can be provided. In the future, human observation means will be more powerful, and there is a high probability that planets much larger than Jupiter may be discovered.