Gas giant

In Astronomy a gas giant is a very large planet, smaller than a brown dwarf.

Brown dwarfs are astronomical objects that, while they lack the mass to become stars, begin fusing hydrogen, and entering the main sequence, do have enough mass for a limited period of Deuterium fusion and Lithium fusion. Thirteen times the mass of Planet Jupiter is considered the lower limit on the mass required to be considered a brown drarf.

Planet Jupiter and Planet Saturn are recognized as gas Giants. Our Solar system's Planet Uranus and Planet Neptune also used to be considered gas Giants, but, recently a new classification, ice giant was created for these smaller, but still quite large planets.

Most of a gas giant consists of Hydrogen and Helium gas. Astronomers used to believe they had a small rocky core. Now there is speculation they have small cores of liquid Hydrogen, explaining their very intense magnetic fields.

As of 2026 the current classifications of Planet sized objects are:

type	mass in Earth masses	notes
brown dwarf	4100 to 25000
Gas giant		Astronomers have not agreed on a lower mass limit on gas Giants, but agree that Planet Saturn, at 95 times Earth's mass, is a gas giant. Thirteen Jupiter masses, of 4100 Earth masses is considered the upper limit on the mass of a gas giant.
Ice giant		Astronomers have not agreed on the lower and upper mass limits on ice Giants, but agree that Uranus and Neptune, at 14 and 17 Earth mess, are ice giants.
sub-Neptune
super-Earth
Earth-like
sub-Earth