Astronomy Activity: Let’s Make a Supernova

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 of 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’re 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 in 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. 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? 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? 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 I’ll count down and we’ll all let go of both falls at once and shout ‘supernova’! You ready? 3-2-1! SUPERNOVA! Thank you! What happened? Everything went flying, that’s right! Good. An explosive shockwave and 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? Vivian: I think I want to make another supernova! Marni: Okay

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