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 has 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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Chapters:
Introduction: Asteroids 00:00
What are Asteroids? 1:37
Structure of the Main Belt 2:18
Ceres's Structure 3:43
Vesta and other Main Belt Asteroids 4:38
Rubble Piles 5:16
Why did the Asteroid Belt form? 6:20
Marscrossing, Apollo, and Aten Asteroids 7:16
Trojan Asteroids & Lagrange Points 8:25
How Asteroids Get Their Names 9:53
Review 10:41


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PHOTOS/VIDEOS
Timelapse of Asteroid 2004 FH's flyby http://en.wikipedia.org/wiki/File:Ast... [credit: NASA/JPL Public Domain]
Asteroid Discovery Video    • Asteroid Discovery   19802014   [credit: Scott Manley [email protected]]
Inner Solar System http://en.wikipedia.org/wiki/File:Inn... [credit: Wikimedia Commons]
Kirkwood gaps http://commons.wikimedia.org/wiki/Fil... [credit: Wikimedia Commons]
Ceres, Earth & Moon size comparison http://en.wikipedia.org/wiki/File:Cer... [credit: NASA]
Dawn Glimpses Ceres’ North Pole http://www.jpl.nasa.gov/news/news.php... [credit: NASA/JPLCaltech/UCLA/MPS/DLR/IDA]
Ceres cutaway http://commons.wikimedia.org/wiki/Fil... [credit: NASA, ESA, and A. Feild (STScI)]
Bright Spot on Ceres Has Dimmer Companion http://www.jpl.nasa.gov/spaceimages/d... [credit: NASA/JPLCaltech/UCLA/MPS/DLR/IDA]
Vesta http://en.wikipedia.org/wiki/4_Vesta#... [credit: NASA/JPLCaltech/UCAL/MPS/DLR/IDA]
Lutetia http://en.wikipedia.org/wiki/21_Lutet... [credit: ESA]
Gaspra http://commons.wikimedia.org/wiki/Fil... [credit: NASA]
Steins http://neo.ssa.esa.int/image/image_ga... [credit: ESA/Osiris]
Mathilde http://neo.jpl.nasa.gov/images/mathil... [credit: NEAR Spacecraft Team, JHUAPL, NASA]
Ida http://en.wikipedia.org/wiki/243_Ida#... [credit: NASA/JPL]
Kleopatra http://apod.nasa.gov/apod/ap000510.html [credit: Stephen Ostro et al. (JPL), Arecibo Radio Telescope, NSF, NASA]
An artist's conception of two Plutosized dwarf planets in a collision around Vega. http://en.wikipedia.org/wiki/Methods_... [credit: NASA/JPLCaltech/T. Pyle (SSC)]
Itokawa http://apod.nasa.gov/apod/ap140209.html [credit: ISAS, JAXA]
An artist's illustration showing two asteroid belts and a planet orbiting Epsilon Eridani http://en.wikipedia.org/wiki/Epsilon_... [credit: NASA/JPLCaltech]
NearEarth Asteroids http://www.jpl.nasa.gov/images/astero... [credit: NASA/JPLCaltech]
Lagrange Points Diagram http://en.wikipedia.org/wiki/Trojan_(... [credit: Wikimedia Commons]
TK7 http://en.wikipedia.org/wiki/2010_TK7... [credit: NASA/JPLCaltech/UCLA]
165347 Philplait http://www.slate.com/content/dam/slat... [credit: Larry Denneau/PanSTARRS via Amy Mainzer]