Phil gives the course a send off with a look at some of his favorite topics.

Our Universe’s days are numbered.

Thanks to the wonders of physics, we can map a timeline of the universe’s history.

Most of the universe is made up of a mysterious entity that pervades space: dark energy.

Thanks to observations of galaxy redshifts, we can tell that the universe is EXPANDING!

Today on Crash Course Astronomy, Phil dives into some very dark matters.

The discovery of gamma-ray bursts is an epic story.

Active galaxies pour out lots of energy.

Galaxies contain gas, dust, and billions of stars or more.

Today we’re talking about our galactic neighborhood: The Milky Way.

Astronomers study a lot of things, but nebulae might be the most beautiful of them all.

Last week we covered multiple star systems, but what if we added thousands to the mix?

Binary stars are gravitationally bound together in the same system.

Stellar mass black holes form when a very massive star dies, and its core collapses.

In the aftermath of a some stars we find a weird little object known as a neutron star.

Massive stars fuse heavier elements in their cores than lower mass stars.

What comes next after the death of a low mass star? A white dwarf.

Today we are talking about the life -- and death -- of stars.

Brown dwarfs have a mass that places them between giant planets and small stars.

There are many other planets outside of our own solar system, but finding them is tricky.

Phil explains stars and how they can be categorized using their spectra.

How do astronomers make sense out of the vastness of space?

In order to understand more of universe, we need to talk a little bit about light.

What the difference between a meteor, meteorite, and meteoroid?

WeÕre heading to the outskirts of the solar system.

Comets are chunks of ice and rock that orbit the Sun.

Now that weÕve finished our tour of the planets, weÕre headed back to the asteroid belt.

WeÕre rounding out our planetary tour with ice giants Uranus and Neptune.

Saturn is the crown jewel of the solar system, beautiful and fascinating

Before moving on from Jupiter, weÕre going to linger for a moment on the planet's moons.

Jupiter is the biggest planet in our solar system.

Mar is the fourth planet from the sun and the outermost of the terrestrial planets.

Venus is a gorgeous naked-eye planet, hanging like a diamond in the twilight.

Mercury is the closest planet to the sun.

Take a look up to the moon's surface features, core, and theories about its formation.

Phil starts the planet-by-planet tour of the solar system right here at home, Earth.

Take a look at the two-octillion ton star that rules our solar system.

Phil takes a look at the explosive history of our cosmic backyard.

What is the relationship between tides and gravity?

Phil looks at how gravity plays out across the universe.

Today Phil explains how telescopes work

"But what about eclipses!?"

Phil takes you through the cause and name of the Moon's phases.

Take a look at the cyclical phenomena that we can see at work in the universe.

Take a look at all the incredible things you can see with your naked eye.

Get to know host Phil Plait and begin with answering a simple question: what is astronomy?