 Now, let's stop talking about supernovae and make one happen. Well, let's make a model of a supernova. Pass out a tennis ball and a ping-pong ball to each person. The tennis ball represents a small part of the core of the star where all the fusion is taking place. The ping-pong ball represents the outer layers of the atmosphere of the star. You may want to first demonstrate to your audience what you are going to do with the balls when you are ready to model a supernova explosion. Hold the ping-pong ball on top of the tennis ball and the whole group of people will let go of both at once, with everyone shouting supernova! To include the radiation generated during the explosion, place the spool representing a gamma ray in between the tennis ball and the ping-pong ball. Then let go of all three at once. You can use the two-handed hold, like this, or the one-handed hold, like this. Make sure there is a little space between the ping-pong ball and your hand. This must be done on a hard surface, like a bare floor or in a parking lot. Heavily carpeted floors or grass lawns don't work as well. To imagine the dimensions of the star and its core, the star has become a red supergiant prior to going supernova. Let's imagine the red supergiant, Betelgeuse, shrunk down so it would fit in the Pacific Ocean. Betelgeuse's core, where all the fusion is taking place, would fit inside a football stadium. When the core reaches iron and the fusion process stops, Betelgeuse's core would collapse from the size of a football stadium to about the size of a basketball. And then, supernova! Refer to the activity write-up for Let's Make a Supernova in the toolkit manual for more details about the science behind this demonstration. Now, let's see how we might do this with a group. Let's imagine we're all inside a massive star, holding a part of the core and a part of the outer layers of the star. Wow, it's hot in here! Everyone toss up one of the balls. There you go. As long as you keep pushing the ball up, it'll stay in the air. What happens if you stop pushing? Gravity takes over. That's right, it falls, sure. Now you're using energy to push the ball up. And what did you say was making the ball come back down? Gravity. Right, whoops, just like that. The same kind of thing happens inside a star. The heat generated by fusion in the core creates pressure, which pushes out on the rest of the star. What happens if the core stops generating heat? Gravity takes over. Now imagine, like I said, we're all standing inside a massive star. In its core, the star continues to fuse atoms into heavier and heavier elements, hydrogen, to helium, to carbon, to silicon, generating lots of heat until we get to iron. Because the fusion process stops at iron, the core stops generating heat, then the core collapses under its own weight, and the outer layers of the star start falling in. And then, let's see what happens. Are you ready to make a supernova? Yeah! All right. Hold your part of the outer layers of the star above your piece of the core, like this. Okay. Good. Down a little farther. There. Now, all count down, and we'll all let go of both balls at once, and shout, supernova! You ready? Three, two, one, supernova! Wow! Thank you. What happened? Everything went flying. That's right. Good. An explosive shockwave in the energy generated from core collapse moves outward, heating the surrounding layers of the star, and boom! Most of the star is blasted into space in a supernova explosion. Would you like to see stars in the sky likely to go supernova at the end of their lives? Yeah! Good. I think I want to make another supernova. Okay.