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Journal 3/2/17 Do you think nebulae help to prove that God exists? Objective Tonight’s Homework To learn more details about the final stages in the life of a star Finish Nebula Research by Monday Planetary Nebulae Pick 2 nebulae from the list and answer the questions below: Thor’s Helmet Helix Nebula Hourglass Nebula Ghost of Jupiter Owl Nebula California Nebula Dumbbell Nebula Red Spider Nebula Homunculus Nebula Butterfly Nebula Veil Nebula Ant Nebula Ring Nebula Footprint Nebula Skull Nebula Eskimo Nebula Camel’s Eye Nebula Box Nebula Bug Nebula Retina Nebula Blue Snowball Nebula Cat’s Eye Nebula Spirograph Nebula Witch’s Broom Nebula Medusa Nebula Stingray Nebula Crab Nebula Red Rectangle Nebula Boomerang Nebula Flame Nebula 1) Find the “NGC” or “IC” number for the nebula. Find what NGC means. 2) How far away is your nebula? How old or big is it? 3) List 5 interesting facts about the nebula 4) Find a good picture of the nebula 5) What is the nebula made of? Notes on Stellar Remnants No matter the size of the star or whether it dies quietly or in a supernova, all stars will form a planetary nebula. The nebula is made out of the gases that got blown from the star. It may look like it expands slowly, but these gases move out at an average of 30 miles/second. Most of this is hydrogen, but we also find oxygen, nitrogen, sulfur, and many others. We can identify the gases by the colors we see. Extra Notes on Stellar Evolution x Extra Notes on Stellar Evolution x Notes on Stellar Remnants When a star dies, if the core has less mass than 1.4 times the sun, it will form a white dwarf. Gravity is trying to squeeze the core as small as it can get. It's stopped by the pressure of electrons trying to repel each other. This pressure counteracts gravity. Over billions of years, this hot core will slowly cool down and fade to become a black dwarf. Notes on Stellar Remnants But what if our star is bigger than this? We said that a star’s life is a constant battle between pressure and gravity. In a normal star, the pressure from fusion balances the pull of gravity. When a star dies, it leaves behind a white dwarf. In this small object, fusion is no longer happening, so the core begins to collapse. Without fusion, what stops it? ? Notes on Stellar Remnants Something called “electron degeneracy pressure”. As the atoms squeeze together, the electrons in each atom don’t want to overlap. The electromagnetic force pushes them apart. This pressure holds up against gravity’s crush. Notes on Stellar Remnants But what if we have an even bigger core? With enough pressure, we can FORCE atoms to let their electrons overlap. This happens for stars with cores up to 3 times heavier than the sun. This is the case with neutron stars. When a big core dies, gravity crushes down, but it crushes even harder than electron degeneracy pressure. As the electrons overlap, they merge with the protons to turn into neutrons. The neutrons all crush together, at which point their neutron pressure is enough to stop the collapse from gravity. Notes on Stellar Remnants So let’s pause here for a second. Neutron stars are very weird because they’re essentially a super-giant atomic nucleus. First, a teaspoon of material from one can weigh up to a billion tons. (A large mountain) Second, an entire neutron star would be smaller than the Denver metro area. (3 times the mass of the whole sun!) Third, if you collapse a spinning thing, it speeds way up. Most neutron stars rotate between 3 and 30 times a second. (24 hours for Earth) Notes on Stellar Remnants These spinning neutron cores usually have crazy strong magnetic fields and shoot out tons of radiation from their poles. As a last point, we think we may have found a few planets orbiting some neutron stars which is really weird. We truly have no idea what such a planet would be like. Notes on Stellar Remnants Crab Nebula Pulsar Notes on Black Holes But if our core is big enough and has enough gravity, even this neutron pressure won’t stop things. Gravity will push the neutrons together and we’ll have gravity alone with no force to push outward. The entire core will keep squeezing down into a single, infinitely small point. Within this point is all the matter that was in the star’s core. Inside, the rules of physics break down. Time and space separate. Exit Question To become a neutron star, a star’s core has to be more than _____ times heavier than the sun, but less than ______ times heavier. 1 / 10 3.2 / 9.5 2.2 / 4 7 / 9.5 1.4 / 3 No one knows