Jupiter is sometimes referred to as a "failed star" because it shares some similarities with stars, but it lacks the necessary mass to ignite nuclear fusion in its core. Here's why:

* Composition: Jupiter is primarily composed of hydrogen and helium, just like stars.

* Gravity: Jupiter's immense gravity pulls in material, much like a star's gravity attracts gas and dust.

* Internal Heat: Jupiter generates internal heat through gravitational pressure, which is also a characteristic of stars.

However, here's why Jupiter isn't a star:

* Mass: Jupiter is about 1/1000th the mass of our Sun. To ignite nuclear fusion, a celestial body needs at least 80 times Jupiter's mass.

* No Nuclear Fusion: Without enough mass, Jupiter's core doesn't reach the extreme temperatures and pressures necessary for hydrogen atoms to fuse into helium, releasing energy and light like stars do.

Therefore, Jupiter is considered a "failed star" because it has the right ingredients and some of the processes, but it doesn't have enough mass to become a true star. It's more accurately classified as a gas giant.