What Planet Gives Off 2 Times as Much Heat as it Receives From the Sun?


My name's Eric Loberg, director of the Taylor Planetarium at the Museum of the Rockies. I'm going to discuss which planet gives off twice as much heat as it receives from the Sun. That planet is Saturn. All of the planets give off a little bit of heat and that's because of radioactive decay. Planets like the Earth have all those elements, they're slowly decaying. And that radioactive decay comes off as heat. So, Earth gives off a little bit of heat, but it doesn't give off nearly as much heat as it receives from the Sun. Because Earth is close, we're receiving all the heat rays from the Sun. The Sun's heat comes down and warms up Earth. And we get so much heat that we don't really even notice how much heat we're giving off. The outer planets are much, much farther from the Sun and that's why we notice that they give off some amount of heat. Jupiter is much closer than Saturn and it gives off about as much heat as it gets from the Sun. Somewhat due to radioactive decay of all of its elements again. But more so, these outer planets, what happens is they're squished and when they're compressed, they have liquid metal cores, maybe some rock underneath that. And that real heat, that heat all comes back out of the planet and warms them up a little bit. So, the planets all started out with a disk and they form into clumps of balls of gas, especially with the outer planets. Jupiter, Saturn, Uranus, Neptune, they clump and there's still a lot of gas in here. But there's a liquid metal and that's hydrogen. Hydrogen gets so pressurized that it actually becomes kind of a liquid metal in the middle and that middle gives off convection heat. This plasma rises up and it actually give off heat out of these planets. And that's what happens with Jupiter which gives out about as much heat as it receives. The balls of gas are mostly hydrogen with a little bit of helium, just like the Sun. Saturn is a little bit different than Jupiter and even the Neptune because Saturn has quite bit more helium. There are some guesses about why, we're not exactly certain why Saturn has more helium. But we know how helium reacts compared to hydrogen, helium is much heavier than hydrogen. So, in the planet Saturn, helium is much more abundant than the other planets and helium will go right through hydrogen, almost like rain. It will fall through the hydrogen and create kinetic energy and that kinetic energy will be shot back out. It's all that potential energy, it's going through the hydrogen, it's warming up the planets and shooting back out. And it warms up Saturn, Saturn gets twice as warm, emits twice as much heat as it gets from the sun. And again, mostly because of how far Saturn is from the Sun. If Saturn was very close to the Sun, it wouldn't be emitting as much heat. But that's your answer, that Saturn goes two times as warm as the Sun. And Neptune is so far out there, we've only sent one mission to it, that's the Voyager Mission. It went by Neptune, and that's all we know about Neptune. We look with our big telescopes, but really don't know that much about Neptune, it's kind of confusing. It gives off two and a half times as much heat as it receives from the Sun. We don't know why, there are some guesses, but we're still not sure. I'm Eric Loberg with the Museum of the Rockies, Taylor Planetarium.

J. Eric Loberg is the manager, lecturer, and program planner at the Taylor Planetarium at the World, a renowned museum of the Rockies in Bozeman, Montana.