Second Sun | Universe Today

Written by Fraser Cain

Have you wondered if we might ever get a second sun here in the Solar System? Maybe Jupiter or Saturn could ignite, becoming stars, or perhaps there's already another star orbiting the Sun, and it could return and cause havoc in the Solar System. Well, don't worry, it's not possible.

When NASA's Galileo spacecraft was nearing the end of its mission, NASA scientists decided that the best thing to do with it was to crash it into Jupiter. This would ensure that Galileo didn't accidently crash into one of Jupiter's moons and contaminate any potential life on those moons. But non-scientists were concerned that crashing Galileo might cause Jupiter to ignite and become a second sun.

But it's not possible. An object becomes a star when it has enough mass crushing down to ignite fusion in its core. This takes about 80 times the mass that Jupiter currently has. Unless Jupiter could somehow gain another 80 times its existing mass, there's no way it could become a star.

Of course, when Galileo did crash into Jupiter, nothing happened. The tiny spacecraft was swallowed up by the enormous planet and crushed by its intense gravity.

NASA is planning to do the same thing with the Cassini spacecraft, and now people on the internet are concerned that this will ignite Saturn into a star. Saturn is even less massive than Jupiter, and would require more than 100 times its current mass before it was heavy enough to ignite nuclear fusion in its core. This idea is called "Project Lucifer".

There's another idea called the Nemesis theory, which proposes that our Sun has a binary companion star, maybe a brown dwarf or even a red dwarf. Every few million years or so, this star passes close to the Solar System and messes up orbits with its gravity. There's some evidence for this theory, since the Earth has a history of extinctions that happen every 65 million years or so. But if this second sun exists, we haven't observed it yet.

We've written many articles about Project Lucifer for Universe Today. Here's a two-part series about it. Here's a link to Part 1, and here's a link to Part 2.

Here's a similar question answered by the Bad Astronomer Phil Plait.

We've recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.

Filed under: Astronomy

Tags: second sun, sun