Twin brown dwarfs. Artwork of the twin brown dwarfs 2M 0939. These are the dimmest brown dwarfs found as of 2010. Brown dwarfs are intermediate objects between a gas giant planet (like Jupiter) and a star. They form out of collapsing clouds of gas and dust, but are not massive enough to trigger the nuclear reactions that form a star. 2M 0939 have cold atmospheres that contain water, methane and ammonia gases.