We know a lot about our Solar System, but there's an awful lot that's a complete and total mystery. Today we're going to begin a series of unknown length examining some of these mysteries, and explain the best theories astronomers have so far.

Last week we talked about Herschel the people – William Herschel, his sister Caroline, and his son John. This week we look at the Herschel Space Observatory, a mission launched in 2009 to reveal the coldest and dustiest regions in the Universe.

Ancient astronomers knew of 5 planets, Mercury, Venus, Mars, Jupiter and Saturn - 6 if you count Earth. But then in 1781, William Herschel discovered an entirely new planet, boosting the number of planets to 7. Let's learn about Herschel, his equipment, his discoveries, and his sister Caroline - an accomplished astronomer of her own.

Even in ancient times, astronomers realized there was something different about the planets - they move! The movement of the planets and their moons are governed by gravity. And as we all know, gravity can do some funny things.

This is going to be one of those weeks where we tackle something you're mentally avoiding. You know all those astronomical terms, like alt-azimuth, right ascension and declination, arc seconds and arc minutes? Of course not, your mind has blocked them out. Today we're going explain them, so you don't need to avoid them any more. Soon, you'll be ready to find anything in the cosmos.

Last week we talked about Fermi the man, now we're going to talk about Fermi the space telescope. That's right, Enrico Fermi made such an impact in the astronomy and physics community that he got a space telescope named after him. Let's take a look at what this mission will do, and its discoveries so far.

Today's episode of Astronomy Cast is about another famous physicist: Enrico Fermi. We've already taken a look at one of Fermi's most famous ideas, the Fermi Paradox - or, where are all the aliens? But let's meet the man behind the ideas, the namesake for the new Fermi mission.

Let's assume that humans survive the next few hundred years without destroying ourselves, or the planet, and we actually become a space faring civilization. What kinds of challenges will we face, and what projects will we build to expand ourselves out into the Solar System and eventually the galaxy. You just need to think big.

What if our universe was just one in an infinite number of parallel universes; a possible outcome from the specific predictions of quantum mechanics. The idea of multiple universes is common in science fiction, but is there any actual science to back this theory up?

You know how a police siren changes sound when it passes by you? That's the doppler effect. It works for sound waves and it works for light waves. Astronomers use the doppler effect to study the motion of objects across the Universe, from nearby extrasolar planets to the expansion of distant galaxies.