For those who don’t know, PBS Spacetime is an awesome youtube series where real-life astrophysicist Matt O’Dowd discusses the most fascinating facts and theories about modern physics. They’ve had videos on everything from String Theory to General Relativity to alien spaceships buzzing our solar system. I’ve loved almost every video and topic they’ve discussed but one glaring omission that I’d love to see more of is planetary science, especially the formation of our solar system.

Our solar system is a weird and wonderful place, and there’s plenty to talk about that they haven’t gotten too. I’m particularly interested in the topic of solar system formation. When I read articles about exoplanets and foreign stars, they often discuss the Hot Jupiters and Super Earths that might be orbiting those. These stories make our solar system, with it’s cold Jupiter and it’s regular-sized Earth seem kind of lame. But how abnormal is our solar system? Are we out of the ordinary, or very ordinary indeed?

One really cool set of hypotheses I’ve read up on are the Nice Model and the Grand Tack. I don’t have near enough astrophysics background to explain these, but together they paint an exciting picture in which, during the early formation of the solar system, Jupiter and Saturn began to drift inward on orbits closer and closer to the sun. Eventually they got to orbits that are much closer to Mars’ orbit than what they have at present, before orbital resonances kicked them back out again into their present orbits. These theories propose to explain a lot of questions about our early solar system: the smallness of Mars relative to the Earth and Venus, how the current gas giants could have formed and reached positions so far away from the sun, and even perhaps explain the Late Heavy Bombardment of the inner solar system. I’ve often been curious if they could also be an explanation for why our sun doesn’t have a Hot Jupiter aka a gas giant orbiting very very close to the Sun. As stated, Jupiter and Saturn migrated inward before eventually turning around and migrating back out again. If they had not stopped, might they have formed a set of Hot Jupiters? Did the Hot Jupiters around other stars migrate inward to their positions, and Jupiter and Saturn once migrated?

It’s a tantalizing topic for me which is why I’d love to see a PBS spacetime episode on it?