Our galaxy's a lot bigger than we thought and more interesting discoveries

(via Bad Astronomy)

In case you didn't know, the center of our galaxy is a supermassive black hole. Here's some perspective: this black hole is 4 million times the mass of our sun, but since there are about 200 billion stars in our galaxy, the mass of this black hole is actually 0.002% of the mass of the galaxy. In other words, if the entire population of Earth represented the total mass of our galaxy, the mass of the black hole would be smaller than the population of Kansas City.

Using a bunch of telescopes around the Earth, astronomers have discovered that our sun orbits this black hole a lot faster than originally thought. Instead of 220 km/s, it actually orbits at 270 km/s. That's over a hundred thousand miles per hour faster!

So what does this mean? Well, since it is the combined gravity of everything in the galaxy between the sun and that black hole that determines that speed, this difference in speed indicates that our galaxy is a full 50% bigger than we originally thought! We used to think that the Andromeda galaxy was the biggest 'in town', but with this new discovery, we're apparently about the same size.

Oh, and also, we also discovered that the Milky Way actually has four spiral arms and not two like we used to think. So we're a lot bigger and we just discovered two more arms. We're ready to take on the world universe.