Here's why:

* Brown dwarfs are "failed stars." They are not massive enough to ignite nuclear fusion in their cores, which is what powers stars like the Sun.

* The Sun is a main-sequence star. It's currently fusing hydrogen into helium in its core, producing the energy that makes it shine.

* The Sun's fate is to become a red giant. As it runs out of hydrogen fuel, it will expand and cool, eventually becoming a red giant star.

* After the red giant phase, the Sun will become a white dwarf. This is a dense, hot remnant of a star's core.

Brown dwarfs are much smaller and cooler than the Sun. They are not formed from the same process as stars, and they never go through the same life cycle.