On this episode of Our Island Universe: What we know about how the planets in our solar system formed and why some are gas giants or ice giants.
Shanil Virani, Director of the John C. Wells Planetarium Harrisonburg, VA.
Follow on Twitter as shanilv
Transcript:
Perhaps the most exciting research area in all of science is that of finding planets around nearby stars. But how did the planets in our Solar System form? And why do we only have two gas giants — Jupiter and Saturn? New work is showing how you can just a few behemoths from a swirling protoplanetary disk of gas and dust.
Turns out the key to making a gas giant is the same as making a snowman. You start with a small amount of snow and you roll it into a big ball! The same is true for planets! This model — pebble accretion — says that planets grow from from small grains through collision and is held together via static electricity. These “pebbles” then coalesce and continue to add more material forming a rocky core. However, this process requires a long amount of time so you typically only have 1 to 4 gas giants like Jupiter & Saturn around a Sun-like star. This model also produces a few ice giants — like Uranus and Neptune — in the right range of distances from its parent star. It also predicts that no large planets would have formed the in the Kuiper belt, that outer fringe where Pluto and its brethren hang out, consistent with observations we’ve made so far. Sorry, there is no Planet X or planet Nibiru out there!
So this winter after the first snowfall when you are outside making a snowman with the kids, remember that the same physics you use to make a large ball of snow explains how the planets in our Solar System began to form 4.5 billion years ago.