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 that were once part of smallish planets but were destroyed after collisions. Most orbit the Sun between Mars and Jupiter, but some get near the Earth. The biggest, Ceres is far smaller than the Moon but still big enough to be round and have undergone differentiation.

CORRECTION: In the episode we say that 2010 TK7 is 800 km away. However, 2010 TK7 stays on average 150 million kilometers from Earth, but that can vary wildly.
Sorry about that!

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Table of Contents
Asteroids Are Chunks of Rock, Metal, or Both 1:45
Most Orbit the Sun Between Mars and Jupiter 7:16
Ceres is Far Smaller Than the Moon, But Large Enough to be Round 3:43

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PHOTOS/VIDEOS
Timelapse of Asteroid 2004 FH's flyby en.wikipedia.org/wiki/File:Asteroid_2004_FH.gif [credit: NASA/JPL Public Domain]
Asteroid Discovery Video www.youtube.com/watch?v=2k2vkLEE4ko [credit: Scott Manley - scottmanley1972@gmail.com]
Inner Solar System en.wikipedia.org/wiki/File:InnerSolarSystem-en.png [credit: Wikimedia Commons]
Kirkwood gaps commons.wikimedia.org/wiki/File:Kirkwood-gaps-as-disk.png [credit: Wikimedia Commons]
Ceres, Earth & Moon size comparison en.wikipedia.org/wiki/File:Ceres,_Earth_%26_Moon_size_comparison.jpg [credit: NASA]
Dawn Glimpses Ceres’ North Pole www.jpl.nasa.gov/news/news.php?release=2015-133 [credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA]
Ceres cutaway commons.wikimedia.org/wiki/File:Ceres_Cutaway.jpg [credit: NASA, ESA, and A. Feild (STScI)]
Bright Spot on Ceres Has Dimmer Companion www.jpl.nasa.gov/spaceimages/details.php?id=PIA19185 [credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA]
Vesta en.wikipedia.org/wiki/4_Vesta#/media/File:Vesta_full_mosaic.jpg [credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA]
Lutetia en.wikipedia.org/wiki/21_Lutetia#/media/File:Lutetia_closest_approach_(Rosetta).jpg [credit: ESA]
Gaspra commons.wikimedia.org/wiki/File:Galileo_Gaspra_Mosaic.jpg [credit: NASA]
Steins neo.ssa.esa.int/image/image_gallery?uuid=db747cf5-9d21-405e-bcdb-e70fe475edc9&groupId=10157&t=1340734455649 [credit: ESA/Osiris]
Mathilde neo.jpl.nasa.gov/images/mathilde1.jpg [credit: NEAR Spacecraft Team, JHUAPL, NASA]
Ida en.wikipedia.org/wiki/243_Ida#/media/File:243_ida_crop.jpg [credit: NASA/JPL]
Kleopatra apod.nasa.gov/apod/ap000510.html [credit: Stephen Ostro et al. (JPL), Arecibo Radio Telescope, NSF, NASA]
An artist's conception of two Pluto-sized dwarf planets in a collision around Vega. en.wikipedia.org/wiki/Methods_of_detecting_exoplanets#/media/File:Massive_Smash-Up_at_Vega.jpg [credit: NASA/JPL-Caltech/T. Pyle (SSC)]
Itokawa apod.nasa.gov/apod/ap140209.html [credit: ISAS, JAXA]
An artist's illustration showing two asteroid belts and a planet orbiting Epsilon Eridani en.wikipedia.org/wiki/Epsilon_Eridani#/media/File:NASA-JPL-Caltech_-_Double_the_Rubble_(PIA11375)_(pd).jpg [credit: NASA/JPL-Caltech]
Near-Earth Asteroids www.jpl.nasa.gov/images/asteroid/20130204/asteroid20130204-full.jpg [credit: NASA/JPL-Caltech]
Lagrange Points Diagram en.wikipedia.org/wiki/Trojan_(astronomy)#/media/File:Lagrange_very_massive.svg [credit: Wikimedia Commons]
TK7 en.wikipedia.org/wiki/2010_TK7#/media/File:PIA14405-full_crop.jpg [credit: NASA/JPL-Caltech/UCLA]
165347 Philplait www.slate.com/content/dam/slate/blogs/bad_astronomy/2014/01/20/asteroidphilplait_panstarrs.jpg.CROP.original-original.jpg [credit: Larry Denneau/Pan-STARRS via Amy Mainzer]

1. Introduction to Astronomy
2. Naked Eye Observations
3. Cycles in the Sky
4. Moon Phases
5. Eclipses
6. Telescopes
7. The Gravity of the Situation
8. Tides
9. Introduction to the Solar System
10. The Sun
11. The Earth
12. The Moon
13. Mercury
14. Venus
15. Mars
16. Jupiter
17. Jupiter's Moons
18. Saturn
19. Uranus & Neptune
20. Asteroids
21. Comets
22. The Oort Cloud
23. Meteors
24. Light
25. Distances
26. Stars
27. Exoplanets
28. Brown Dwarfs
29. Low Mass Stars
30. White Dwarfs & Planetary Nebulae
31. High Mass Stars
32. Neutron Stars
33. Black Holes
34. Binary and Multiple Stars
35. Star Clusters
36. Nebulae
37. The Milky Way
38. Galaxies, part 1
39. Galaxies, part 2
40. Gamma-Ray Bursts
41. Dark Matter
42. The Big Bang, Cosmology part 1
43. Dark Energy, Cosmology part 2
44. A Brief History of the Universe
45. Deep Time
46. Everything, The Universe...And Life
47. Explore The Solar System:

In this Crash Course series, marvel at the wonders of astronomy with your host for this intergalactic adventure, the Bad Astronomer himself -- Phil Plait. In just 40 short lessons, you will learn the basics of the oldest science known to humanity.

Be sure to check out links to relevant Photos in the description for each video.