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 space. They can glow on their own or reflect light from nearby stars. When they glow it’s usually predominantly red from hydrogen and green from oxygen, and when they reflect and scatter light it’s from massive hot stars, so they look blue. Stars are born in some nebulae, and create new ones as they die. Some nebulae are small and dense, others can be dozens or hundreds of light years across.

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Table of Contents
Nebulae Are Clouds of Gas And/Or Dust 0:42
They Can Emit Light Or Reflect It 1:20
Elements Change Their Glow 3:31
Nebulae Can Create Stars 5:28

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PHOTOS/VIDEOS
Saturn www.flickr.com/photos/badastronomy/10328043663/sizes/o/in/photostream/ [credit: Photo by NASA / JPL / Space Science Institute / Gordan Ugarkovic]
Carina Nebula www.spacetelescope.org/news/heic0707/ [credit: NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team (STScI/AURA)]
Crab Nebula sci.esa.int/herschel/53338-herschel-and-hubble-composite-image-of-the-crab-nebula/ [credit: ESA/Herschel/PACS/MESS Key Programme Supernova Remnant Team; NASA, ESA and Allison Loll/Jeff Hester (Arizona State University)]
Carina Jets www.spacetelescope.org/images/heic1007a/ [credit: NASA, ESA, M. Livio and the Hubble 20th Anniversary Team (STScI)]
The Twin Jet Nebula www.spacetelescope.org/images/heic1518a/ [credit: ESA/Hubble & NASA]
Tycho's Supernova Remnant chandra.harvard.edu/photo/2011/tycho/ [credit: X-ray: NASA/CXC/Rutgers/K.Eriksen et al.; Optical: DSS]
Ring Nebula's True Shape hubblesite.org/newscenter/archive/releases/2013/13/image/a/ [credit: NASA, ESA, C.R. O'Dell (Vanderbilt University), and D. Thompson (Large Binocular Telescope Observatory)]
3D animation of the Orion nebula www.spacetelescope.org/videos/astro_bo/ [credit: ESO/M. Kornmesser]
Stardust stardust.jpl.nasa.gov/images/science/idp-m.jpg [credit: NASA]
From the Pleiades to the Hyades www.deepskycolors.com/archive/2011/11/06/from-the-Pleiades-to-the-Hyades.html [credit: Rogelio Bernal Andreo]
How to Become a Star www.eso.org/public/images/eso0102a/ [credit: ESO]
The Orion Nebula www.eso.org/public/images/eso1103a/ [credit: ESO/Igor Chekalin]
Trapezium Cluster in the Orion Nebula www.spacetelescope.org/images/opo0019b/ [credit: K.L. Luhman (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.); and G. Schneider, E. Young, G. Rieke, A. Cotera, H. Chen, M. Rieke, R. Thompson (Steward Observatory, University of Arizona, Tucson, Ariz.) and NASA/ESA]
PIA08656 www.jpl.nasa.gov/spaceimages/images/largesize/PIA08656_hires.jpg [credit: NASA/JPL-Caltech/IRAS/H. McCallon]
Edge-On Protoplanetary Disc in the Orion Nebula www.spacetelescope.org/images/opo9545h/ [credit: Mark McCaughrean (Max-Planck-Institute for Astronomy), C. Robert O'Dell (Rice University), and NASA/ESA]
Hubble's sharpest image of the Orion Nebula with proplyd highlights www.spacetelescope.org/images/heic0917ab/ [credit: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA), the Hubble Space Telescope Orion Treasury Project Team and L. Ricci (ESO)]
Young Stellar Disks in Infrared www.spacetelescope.org/images/opo9905b/ [credit: D. Padgett (IPAC/Caltech), W. Brandner (IPAC), K. Stapelfeldt (JPL) and NASA/ESA]
The Eagle Nebula, M16 www.noao.edu/image_gallery/html/im0725.html [credit: T.A.Rector (NRAO/AUI/NSF and NOAO/AURA/NSF) and B.A.Wolpa (NOAO/AURA/NSF)]
Pillars of Creation hubblesite.org/newscenter/archive/releases/2015/01/image/e/warn/ [credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)]
Planetary Nebula HFG1 www.noao.edu/image_gallery/html/im1110.html [credit: T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF)]
Zooming in on the Horsehead Nebula www.spacetelescope.org/videos/heic1307c/ [credit: NASA, ESA, and G. Bacon (STScI); ESO]
Orion, from Head to Toes www.deepskycolors.com/archive/2010/10/22/orion-from-Head-to-Toes.html [credit: Rogelio Andreo Bernal]
Sifting through Dust near Orion’s Belt (mouseover comparison) www.eso.org/public/images/comparisons/eso1219a/ [credit: ESO/APEX (MPIfR/ESO/OSO)/T. Stanke et al./Igor Chekalin/Digitized Sky Survey 2]

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.