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 of stars or more. They come in four main shapes: elliptical, spiral, peculiar, and irregular. Galaxies can collide, and grow in size by eating each other.

Check out the Crash Course Astronomy poster here:

Introduction: Galaxies 00:00
Spiral Galaxies 3:00
Elliptical Galaxies 5:22
Galactic Collisions 6:18
Peculiar Galaxies 8:46
Irregular Galaxies 9:29
Review 11:08

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NGC 5363 [credit: T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF)]
Panorama of Spiral Galaxy, M31 [credit: Local Group Survey Team and T.A. Rector (University of Alaska Anchorage)]
Animation of a variable star [credit: NASA, ESA, M. Kornmesser]
Hubble M31 PHAT Mosaic [credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler]
Elliptical – Death of giant galaxies spreads from the core [credit: ESA/Hubble & NASA]
Spiral – HUBBLE VIEW OF BARRED SPIRAL GALAXY MESSIER 83 [credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Credit: William Blair (Johns Hopkins University)]
Peculiar – Colliding galaxies make love, not war [credit: NASA, ESA, and the Hubble Heritage Team STScI/AURA)-ESA/Hubble Collaboration]
Irregular – Little Galaxy Explored [credit: NASA/JPL-Caltech/STScI]
Hubble Image of Messier 101 [credit: NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana), and STScI]
A poster-size image of the beautiful barred spiral galaxy NGC 1300 [credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA)]
NGC 3344 [credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona]
Flocculent spiral NGC 2841 [credit: NASA, ESA and the Hubble Heritage Team]
Barred Spiral Galaxy NGC1365 [credit: SSRO/PROMPT and NOAO/AURA/NSF]
Magnificent Details in a Dusty Spiral Galaxy [credit: The Hubble Heritage Team]
Panning across Messier 77 [credit: NASA, ESA, Digitized Sky Survey 2. Acknowledgement: A. van der Hoeven]
Hubble Mosaic of the Sombrero Galaxy [credit: NASA/ESA and The Hubble Heritage Team]
Spiral Galaxy NGC 4565 [credit: ESO]
M87 (with Jet) [credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona]
M59, NGC4621 [credit: NOAO/AURA/NSF]
Fulldome simulation of colliding galaxies [credit: NASA/STScI]
Antennae Galaxies [credit: ESA/Hubble & NASA]
Terzan 5 Artist’s Concept [credit: Amanda Smith, Institute of Astronomy, University of Cambridge]
Interacting Galaxy Pair Arp 87 [credit: NASA, ESA, and the Hubble Heritage Team]
Doing cartwheels to celebrate the end of an era [credit: ESA/Hubble & NASA]
Hoag’s Object [credit: NASA and The Hubble Heritage Team]
Paranal Nights [credit: Y. Beletsky (LCO)/ESO]
Tarantula Nebula [credit: TRAPPIST/E. Jehin/ESO]
Hubble Ultra Deep Field 2014 [credit: NASA, ESA]