What's happening this week in Main Lesson

We finally understand on a chemical level how we could possibly be made of star stuff!

Our favorite force in the universe, gravity, came into play in a major way again this week as we talked about the birth and death of stars.  Stars start out in nebulae as hydrogen atoms but gravity makes them attracted to one another and before you know it they are bumping against one another and a huge amount of pressure from gravity makes a dense core. When the temperature in the hydrogen core rises to 18 million degrees, fusion happens and we have a shining star. Eventually, the hydrogen will be fused into helium and the process will continue until the core gets so hot (180 million degrees) that it turns into iron.  At this point, a low-mass star such as our sun will be a Red Giant and will explode into a planetary nebula. Our sun will expand in diameter until it reaches Earth.  Don't worry!  We won't be here in 4.5 billion years to be vaporized! However, a high-mass star such as Betelgeuse will supernova and can turn into a neutron star or a black hole if it's mass is greater than 20 times that of our sun.  When a low-mass star explodes, it releases up to the first 26 elements in the Periodic Table. But when a high-mass star supernova's, it releases all the elements in the Periodic Table (except those that are man-made)! All of the elements are created in the birth and death of stars and this is what we are made of!  I think Gru from Despicable Me would say,"Lightbulb!" 

All the mass of a huge, high-mass star can collapse into a single point of infinite density, a black hole.  A real black hole formed from a massive star that is 200 million times the mass of our sun is smaller that the tip of a pencil!  Imagine all that mass compressed into a singularity!  NGC 4486 is a black hole seen in the Virgo constellation that is 50 million light years away.  The distance from one side of the event horizon (the point of no return) to the other is the same distance as Pluto's orbit. This supermassive black hole is estimated to have the mass of 3 billion suns!  To demonstrate the formation of a black hole, we blew up balloons (star's core) and covered them with two layers of foil (outer layers of the star that explode off).  Inside the core, the heat created by fusion exerts a pressure on the gas layers of the star, which keeps them from collapsing.  So, we lightly compressed the balloons to see how the core cannot collapse at this stage.  When a star runs out of fuel at the end of its life, the core can't hold up the gas layers.  The kids popped the balloons to simulate the core collapsing and then compressed the foil into a ball, which simulates the formation of a black hole. We took note that the mass of the ball was still the same even though it was now smaller.  


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