Astronomy Study Notes: Interstellar Medium, Sun's Energy, and Stellar Evolution, Study notes of Astronomy

Download Astronomy Study Notes: Interstellar Medium, Sun's Energy, and Stellar Evolution and more Study notes Astronomy in PDF only on Docsity! Note: - Test, tomorrow, show up early/on-time. - If you want old discussion handouts or study guides, go to www.astro.umd.edu/~wei/astr101.html - Makeup labs are this week. If I talked to you about having a makeup lab, please show up at the time we agreed on, in the regular lab room. Bring your lab book. If I didn’t talk to you, you don’t have to come to lab. ---------------------------------------------------------------------------------------------------------- Practice Test Interstellar Medium - There could very well be a short answer question on the interstellar medium (what we did in discussion and lab last week). There wasn’t one on the test last semester, but topics she can drill you on: - What causes an emission nebula (filament, planetary nebula, HII region) to glow red? o Starlight ionizes (tears electron away) the clouds of hydrogen around it. When the hydrogen regains the electron, the electron falls down to lower levels and emits red light (H alpha emission). - What causes a reflection nebula to be blue? o The dust in the nebula scatters blue starlight towards us. - Name some of the things in the interstellar medium and describe how we see them. o Emission nebula – dark blobs/clouds that show up on the red filter image. o Reflection nebula – dark blobs/clouds that show up on the blue filter image. o Dust clouds – light/bright regions in the images. Blocks out all the light that comes from stars and stuff. - Remember we were looking at negatives in class, so what was dark is actually light, and vice. - Read the descriptions of each type of ISM in your lab 11. Sun’s Energy - The center of the sun is so massive and dense due to gravity that the strong nuclear force fuses the protons (NOT ATOMS – don’t EVER say atoms) together. - The p-p chain (proton-proton chain) converts hydrogen into helium. - There’s some extra mass in the p-p chain, which is turned into energy. - The energy pushes outwards against gravity to keep the star stable and shining. Sun’s Life - Sun produces energy by hydrogen fusion – which produces helium - When the sun runs out of hydrogen in the center (it’s all helium there, now), it contracts. - The contraction makes the core hot and dense, which allows helium fusion in the center and hydrogen fusion in the outer shell - This creates too much energy, which makes it expand into a red giant. - The energy blows off the outer layer of the sun, and it becomes a white dwarf. White Dwarfs - The end state of lower mass stars, like our sun. See “lifetime of a star similar to our sun” on the study guide. - After the star reaches the red giant state, extra energy from core pushes gas out as planetary nebula, core collapses into white dwarf. - White dwarfs are the size of the earth, supported by electron pressure – electrons are forced so close together they exert outward pressure. Big Stars - The bigger the star (towards the left of the HR diagram on the main sequence), the shorter their lives are. - Every “stage” of life is shorter for a high mass star. - For the really big, hot stars, they fuse more complicated stuff (b/c of higher temperatures). Layers like an onion. - Key point – the elements that the big star creates gets more and more complicated on the periodic table of elements, until it reaches iron, which doesn’t release any energy - Then… COLLAPSE! SUPERNOVA! - This only happens for very massive stars – stars that are 10x the mass of the sun or more. - What’s left? A Neutron Star. Neutron Stars - Size of Long Island! Very tiny. - Supported by neutrons packed together tightly – neutron pressure. - Spins very fast. We can see them as pulsars. Pulsars - A spinning neutron star. - !!!!!!At the magnetic poles, fast moving electrons in a strong magnetic field produce radio waves.!!!!!! - When the magnetic axis is pointed towards us we see a “bleep”, when it is pointed away from us we don’t see anything. - Draw a picture and label it if you’re asked this question on the test!