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Comets: Crash Course Astronomy #21

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 into gas, forming the long tail, and also releases dust that forms a different tail. We’ve visited comets up close and found them to be lumpy, with vents in the surface that release the gas as ice sublimates. Eons ago, comets (and asteroids) may have brought a lot of water to Earth — as well as the ingredients for life.

Table of Contents
Comets Are Chunks of Rock and Ice That Orbit the Sun 1:26
When They Get Near the Sun They Turn Into Gas 2:08
Comets Release Gas Via Vents As Ice Sublimates 2:15
Comets May Have Brought Water and Ingredients for Life to Earth 9:30

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PHOTOS/VIDEOS
Halley’s Comet, 1910 [credit: New York Times, Wikimedia Commons]
Bayeux Tapestry [credit: Wikimedia Commons]
Comet McNaught [credit: Phil Plait]
Comet McNaught + tail [credit: Chris North, Wikimedia Commons]
Comet surface [credit: ESA/Rosetta/NAVCAM]
Fine structure in the comet’s jets [credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]
Comet Halley [credit: Halley Multicolor Camera Team, Giotto Project, ESA]
Comet McNaught [credit: ESO]
Hubble’s Last Look at Comet ISON Before Perihelion
[credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)]
Hale-Bopp: The Great Comet of 1997 [credit: Jerry Lodriguss, used with permission]
Sungrazer video [credit: NASA’s Goddard Space Flight Center]
“Large Web” graphic [credit: JHUAPL/SwRI/Dan Durda]
Comet Daniel [credit: Max Wolf, Wikimedia Commons]
Vega 1 Low Res [credit: Russian Academy of Sciences]
The Nucleus of Comet Halley [credit: ESA/MPS]
Comet Hartley 2 [credit: NASA/JPL-Caltech/UMD]
Comet 67P/Churyumov-Gerasimenko [credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]
OSIRIS Catches Activity in the Act [credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]
Active Pit [credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]
Depiction of Philae‍‍ ‘​‍s planned touchdown on the comet [credit: DLR, CC-BY 3.0, Wikimedia Commons]
Colour Image of a Comet [credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]
Comet Lovejoy [credit: NASA/Dan Burbank]
NASA’s Stardust [credit: NASA/JPL]
Comet dust [credit: NASA]
Comet Lovejoy [credit: ESO/G. Brammer]