字幕表 動画を再生する 英語字幕をプリント What if Jupiter gained just a little bit more mass during its formation period, and then ignited to become a star? This is WHAT IF, and here's what would happen if Jupiter became a star. Jupiter has more than twice the mass of all the planets in the Solar System combined. It doesn't have a solid ground, and is made up of the same elements as the Sun. And yet, it's not a star. Jupiter doesn't have enough mass to initiate a fusion reaction in its core - the necessary requirement to be accepted into the star club. If only we could find 79 more Jupiters and crash them all into the one we have now, we'd be able to build a second star in the Solar System. What would that be like? Eighty Jupiters crushed together would make a star out of the gas giant. But that star would be nothing like the Sun. Jupiter would be massive enough to become a red dwarf - a small, cool, hydrogen-burning star. As every red dwarf out there, it wouldn't be too bright. 0.3% of the Sun's luminosity is the most light that Jupiter could hope to spit out. Because Jupiter is four times further away from us than the Sun, the Earth wouldn't get much heat from it. By and large, Jupiter turning into a red dwarf wouldn't change anything for life on Earth. You'd still see it from Earth. A Jupiter-star would appear red and a bit brighter than the Moon at its full phase. Would it at least have a gravitational impact on the Solar System? Not as much as you might think. The former gas giant would slightly shift the orbits of the other planets. But not enough to set them on a collision course with one another, or launch them out of their orbits into outer space. The only threat we'd face would be space rocks from the asteroid belt that Jupiter might send towards the Earth. We'd need to learn to detect and destroy them before they could reach our planet. Other than that, not much would change for the Solar System. Things would get a lot more fun if Jupiter was replaced with a Sun-like star. If our gas giant became 1,000 times more massive, the Solar System would go wild. Asteroids would crash into planets, and planets would change their orbital course. It's hard to predict what would happen to Earth in this gravitational mess. It could be anything from being pulled a little too close to Jupiter-star and getting scorched, to being left drifting alone in the void of space. In any case, it wouldn't be too pretty. In the real world, Jupiter is forever destined to be a planet. And that's for the best. Maybe someday soon we'll get a closer look, and send a manned spacecraft rushing inside the gas giant. But that's a story for another WHAT IF.