Recently in the news, there was an announcement that astronomers had planets orbiting stars in other galaxies. This is both expected and amazing at the same time. First lets talk about how it's expected, it is expected because of our current understanding of how stars are formed. Star formation begins with a huge cloud of gas and dust called a nebula gravitationally collapsing in on itself. This causes the center of the nebula to slowly increase in pressure and temperature. Now to go along with this, if the nebula has even the tiniest rotation, this rotation would steadily speed up during the collapse, and as time goes on, this rotation would actually spin all of the dust and gas into a disk.
There's similar physic going on when you take a blob of pizza dough and you throw it into the air with a twist. If you do this enough times, it will spin itself into a disc. So eventually the center of this disc reaches a critical temperature and pressure such that a star is born and all of the other gas and dust in the disk will begin to gravitationally collect together to form various rocky planets, rocky moons, gas planets, ice comets, etc. All the stuff we find in a star system like ours. So when a star forms, it naturally forms its own planets around it. That is why finding planets around stars is actually expected.
Now stay tuned for our next installment to find out why this discovery of planets around stars in other galaxies is so amazing.
Follow your curiosity to the Fred G. Dale Planetarium at Wayne State College.