Massive stars fuse heavier elements in their cores than lower mass stars. This leads to the creation of heavier elements up to iron. Iron robs critical energy from the core, causing it to collapse. The shock wave, together with a huge swarm of neutrinos, blast through the star’s outer layers, causing it to explode. The resulting supernova creates even more heavy elements, scattering them through space. Also, happily, we’re in no danger from a nearby supernova.

Crash Course Astronomy Poster: store.dftba.com/products/crashcourse-astronomy-poster

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Table of Contents
Massive Stars Fuse Heavier Elements Up To Iron 1:15
Iron Uses High Amounts of Energy, Thus Making Stars Collapse 3:58
The Resulting Supernova Creates Even Heavier Elements 10:00
Relax, Something Else Will Kill You 9:04

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PHOTOS/VIDEOS
Blowing Bubbles chandra.harvard.edu/resources/animations/pne.html [credit: NASA/CXC/April Jubett]
The Sizes of Stars www.eso.org/public/images/eso1030c/ [credit: ESO/M. Kornmesser]
Red giants commons.wikimedia.org/wiki/File:Redgiants.svg [credit: Wikimedia Commons]
Alpha Orionis imgsrc.hubblesite.org/hu/db/images/hs-1996-04-a-print.jpg [credit: A. Dupree (CfA), NASA, ESA]
Sun and VY Canis Majoris commons.wikimedia.org/wiki/File:Sun_and_VY_Canis_Majoris.svg [credit: Wikimedia Commons]
Witch Head Nebula and Rigel www.deepskycolors.com/archive/2009/11/16/witch-Head-Nebula-and-Rigel.html [credit: Rogelio Bernal Andreo]
Layers of a massive star en.wikipedia.org/wiki/User:FT2/scc#/media/File:Massive_star_cutaway_pre-collapse_(pinned,_8M%2B).png [credit: Wikimedia Commons]
NASA's Swift Reveals New Phenomenon in a Neutron Star www.nasa.gov/mission_pages/swift/bursts/new-phenom.html#.VcvAYflVhBd [credit: NASA's Goddard Space Flight Center]
What is a black hole? www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-black-hole-k4.html [credit: NASA/CXC/M.Weiss]
The Death of Stars www.spacetelescope.org/videos/hubblecast52a/ [credit: ESA/Hubble]
Giant Mosaic of the Crab Nebula www.nasa.gov/multimedia/imagegallery/image_feature_460.html [credit: NASA, ESA, J. Hester (Arizona State University)]
Hubble and Chandra spot a celestial bauble www.spacetelescope.org/images/heic1018b/ [credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and NASA/CXC/SAO/J. Hughes]
Vela Supernova Remnant www.glitteringlights.com/Images/Nebulae/i-pqWFzmt/O [credit: Marco Lorenzi]
Spica [credit: Phil Plait]
Cassiopeia A en.wikipedia.org/wiki/Cassiopeia_A#/media/File:Cassiopeia_A_Spitzer_Crop.jpg [credit: Oliver Krause (Steward Observatory) George H. Rieke (Steward Observatory) Stephan M. Birkmann (Max-Planck-Institut fur Astronomie) Emeric Le Floc'h (Steward Observatory) Karl D. Gordon (Steward Observatory) Eiichi Egami (Steward Observatory) John Bieging (Steward Observatory) John P. Hughes (Rutgers University) Erick Young (Steward Observatory) Joannah L. Hinz (Steward Observatory) Sascha P. Quanz (Max-Planck-Institut fur Astronomie) Dean C. Hines (Space Science Institute)]
Sloshing Supernova svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11735 [credit: NASA's Goddard Space Flight Center Video and images courtesy of NASA/JPL-Caltech]
Star Burst svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11447 [credit: NASA's Goddard Space Flight Center Video courtesy of ESA/Hubble/L. Calcada]

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.