Kids: Is Jupiter a failed star?
Michele Fisher, Tokyo, Japan Age: 7 years old.
Cody in Wichita, Kansas, wants to know, “Why do people sometimes call Jupiter a failed star?”
Jupiter is the largest planet in our solar system. In fact, if you were from another solar system, you might consider our local star our sun – and the planet Jupiter to be the only noteworthy objects here.
So Jupiter is really big compared to Earth and all the other planets. But Jupiter is still small compared to the sun. It’s about a thousand times less massive than the sun. In other words, you could fit a thousand Jupiters inside the sun! Jupiter isn’t massive enough to be a star. Stars have to have enough mass to get hot enough inside to spark thermonuclear fusion reactions. Those sorts of reactions produce energy – and that’s what makes stars shine.
Astronomers have determined that – to be even the tiniest, littlest sort of star – Jupiter would have to have 80 times more mass than it does now. If it had this extra mass, it would have thermonuclear fusion reactions in its interior – and it would shine like a star.
And since that’ll never happen, you sometimes hear people called Jupiter a “failed” star.
