Today Phil’s explaining the stars and how they can be categorized using their spectra. Together with their distance, this provides a wealth of information about them including their luminosity, size, and temperature. The HR diagram plots stars’ luminosity versus temperature, and most stars fall along the main sequence, where they live most of their lives.

--

Table of Contents
Stars Can Be Categorized Using Their Spectra 1:32
Spectra With Distance Can Identify Luminosity, Size, and Temperature 5:20
The HR Diagram Plots Luminosity vs Temperature 6:33
Most Stars Fall Along the Main Sequence 7:16

--

PBS Digital Studios: youtube.com/pbsdigitalstudios

Follow Phil on Twitter: twitter.com/badastronomer

Want to find Crash Course elsewhere on the internet?
Facebook - www.facebook.com/YouTubeCrashCourse
Twitter - www.twitter.com/TheCrashCourse
Tumblr - thecrashcourse.tumblr.com
Support CrashCourse on Patreon: www.patreon.com/crashcourse

--

PHOTOS/VIDEOS
Stars www.nasa.gov/images/content/703724main_potw1244a.jpg [credit: ESA/Hubble & NASA]
Spitzer Spectrum www.jpl.nasa.gov/spaceimages/details.php?id=PIA03242 [credit: NASA/JPL-Caltech/Leiden/SRON]
Sun spectrum www.noao.edu/image_gallery/html/im0600.html [credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF]
Annie Jump Cannon en.wikipedia.org/wiki/Annie_Jump_Cannon#/media/File:Annie_Jump_Cannon_1922_Portrait.jpg [credit: New York World-Telegram and the Sun Newspaper]
Cecilia Payne-Gaposchkin en.wikipedia.org/wiki/Cecilia_Payne-Gaposchkin#/media/File:Cecilia_Helena_Payne_Gaposchkin_(1900-1979)_(3).jpg [credit: Smithsonian Institution]
OBAFGKM www.noao.edu/image_gallery/html/im0649.html [credit: NOAO/AURA/NSF]
Betelgeuse www.eso.org/public/usa/images/eso0927e/ [credit: ESO/Digitized Sky Survey 2. Acknowledgment: Davide De Martin]
Sirius www.nasa.gov/multimedia/imagegallery/image_feature_468.html [credit: NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester)]
Solar AM0 spectrum with visible spectrum background commons.wikimedia.org/wiki/File:Solar_AM0_spectrum_with_visible_spectrum_background_(en).png [credit: Danmichaelo, Wikimedia Commons]
Blue sky www.pexels.com/photo/sky-sunny-clouds-cloudy-3768/ [credit: Skitter Photo]
Hawaii sunset photo [credit: Phil Plait]
Hertzsprung-Russell Diagram commons.wikimedia.org/wiki/File:ESO_-_Hertzsprung-Russell_Diagram_(by).jpg [credit: ESO]

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.