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Welcome to the first episode of Crash Course Astronomy. Your host for this intergalactic adventure is the Bad Astronomer himself, Phil Plait. We...

Phil invites you to head outside and take a look at all the incredible things you can see with your naked eye.

This week we build on our naked eye observations from last week and take a look at the cyclical phenomena that we can see at work in the universe.

In this episode of Crash Course Astronomy, Phil takes you through the cause and name of the Moon's phases.

The big question in the comments last week was, "BUT WHAT ABOUT ECLIPSES?" Today, Phil breaks 'em down for you.

Today Phil explains how telescopes work and offers up some astronomical shopping advice.

In today's episode, Phil looks at how gravity plays out across the universe.

Today Phil explores the world of tides! What is the relationship between tides and gravity? How do planets and their moons become tidally locked?...

In today's Crash Course Astronomy, Phil takes a look at the explosive history of our cosmic backyard. We explore how we went from a giant ball of gas...

Phil takes us for a closer (eye safe!) look at the two-octillion ton star that rules our solar system. We look at the sun's core, plasma, magnetic...

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

Join Phil for a tour of our capital-M Moon, from surface features, inside to the core, and back in time to theories about its formation.

Mercury is the closest planet to the sun. It has no atmosphere and is, as such, covered in craters. It's also incredibly hot but, surprisingly, has...

Venus is a gorgeous naked-eye planet, hanging like a diamond in the twilight -- but it’s beauty is best looked at from afar. Even though...

The fourth planet from the sun and the outermost of the terrestrial planets, Mars has long been a popular spot for missions and imagination. Phil...

Jupiter is the biggest planet in our solar system. The gas giant is NOT a failed star, but a really successful planet! It has a dynamic atmosphere...

Before moving on from Jupiter to Saturn, we’re going to linger for a moment on Jupiter’s moons. There are 67 known moons, and 4 huge ones...

Saturn is the crown jewel of the solar system, beautiful and fascinating. It is a gas giant, and has a broad set of rings made of ice particles....

Today we’re rounding out our planetary tour with ice giants Uranus and Neptune. Both have small rocky cores, thick mantles of ammonia, water,...

Now that we’ve finished our tour of the planets, we’re headed back to the asteroid belt. Asteroids are chunks of rock, metal, or both...

Today on Crash Course Astronomy, Phil explains comets. Comets are chunks of ice and rock that orbit the Sun. When they get near the Sun the ice turns...

Now that we’re done with the planets, asteroid belt, and comets, we’re heading to the outskirts of the solar system. Out past Neptune are...

Today Phil helps keep you from ticking off an astronomer in your life by making sure you know the difference between a meteor, meteorite, and...

In order to understand how we study the universe, we need to talk a little bit about light. Light is a form of energy. Its wavelength tells us its...

How do astronomers make sense out of the vastness of space? How do they study things so far away? Today Phil talks about distances, going back to...

Today Phil’s explaining the stars and how they can be categorized using their spectra. Together with their distance, this provides a wealth of...

Today Phil explains that YES, there are other planets out there and astonomers have a lot of methods for detecting them. Nearly 2000 have been found...

While Jupiter is nowhere near massive enough to initiate fusion in its core, there are even more massive objects out there that fall just short of...

Today we are talking about the life -- and death -- of stars. Low mass stars live a long time, fusing all their hydrogen into helium over a trillion...

Today Phil follows up last week’s look at the death of low mass stars with what comes next: a white dwarf. White dwarfs are incredibly hot and...

Massive stars fuse heavier elements in their cores than lower mass stars. This leads to the creation of heavier elements up to iron. Iron robs...

In the aftermath of a 8 – 20 solar mass star’s demise we find a weird little object known as a neutron star. Neutrons stars are...

We’ve covered a lot of incredible stuff, but this week we’re talking about the weirdest objects in space: BLACK HOLES. Stellar mass black...

Double stars are stars that appear to be near each other in the sky, but if they’re gravitationally bound together we call them binary stars....

Last week we covered multiple star systems, but what if we added thousands or even millions of stars to the mix? A star cluster. There are different...

Astronomers study a lot of gorgeous things, but nebulae might be the most breathtakingly beautiful of them all. Nebulae are clouds of gas and dust in...

Today we’re talking about our galactic neighborhood: The Milky Way. It’s a disk galaxy, a collection of dust, gas, and hundreds of...

The Milky Way is our neighborhood in the universe. It’s a galaxy and there are many others out there. Galaxies contain gas, dust, and billions...

Active galaxies pour out lots of energy, due to their central supermassive black holes gobbling down matter. Galaxies tend not to be loners, but...

Gamma-ray bursts are not only incredible to study, but their discovery has an epic story all its own. Today Phil takes you through some Cold War...

Today on Crash Course Astronomy, Phil dives into some very dark matters. The stuff we can actually observe in the universe isn’t all there is....

Thanks to observations of galaxy redshifts, we can tell that the universe is EXPANDING! Knowing that the universe is expanding and how quickly its...

The majority of the universe is made up of a currently mysterious entity that pervades space: dark energy. We don’t know exactly what it is,...

Thanks to the wonders of physics, astronomers can map a timeline of the universe’s history. Today, Phil’s going to give you an overview...

As we approach the end of Crash Course Astronomy, it’s time now to acknowledge that our Universe’s days are numbered. Stars will die out...

Here it is, folks: the end. In our final episode of Crash Course Astronomy, Phil gives the course a send off with a look at some of his favorite...

Carl Sagan covers a wide range of scientific subjects, including the origin of life and a perspective of our place in the universe.

From the planets to the stars and out to the edge of the unknown, history and science collide in a wondrous yet deadly adventure through space and...

Professor Brian Cox explores the dramatic lives of the eight majestic planets/worlds that make up our solar system.

Search for Second Earth brings to life, in breathtaking CGI, an epic future journey that our species has already begun: the voyage of an autonomous...

Famed astrophysicist Neil deGrasse Tyson provides clarity for the vision of the cosmos as he voyages across the universe with never-before-told...