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Transcript
• • • • • • • • • • • • • • • • • • Objectives Life of Stars – Part 1 Name the force that tries to compress/collapse a star? Name the process that happens in the core of a star preventing collapse and powering the star. What is fusion? Why is it important to a star? What is converted to energy in the fusion process? About how long does our star live as a main sequence star? Explain why a massive star only lives a short time? What elements are created in a sun-like star? What elements are created in a massive star? Evolution of the Sun – Part 2 Name and briefly describe the stages that our sun will go through as it ages. About how long does our sun live as a main sequence star? About how much longer does Earth have until our sun evolves to a Red Giant? What is a planetary nebula? Supernovas – Part 3 Describe a supernova. Name two types (Ia and II) of supernovas and briefly describe the events that happen in each case. Name and describe the leftovers from a supernova (expanding gas cloud and neutron star). What is meant by “standard candle”? Describe a neutron star and a pulsar. Why are supernovas important? Why can we say that we are made of stardust? Name and describe the stages in the evolution of a sun-like star. Name and describe the stages in the evolution of large mass star. 1. Life and Death of Stars 2. Evolution of our Star – the Sun 3. Supernovas Part 1 Life and Death of All Stars (Determined by MASS of star) •Gravity pulls in •Energy from fusion pushes out Balance = Stable star Balance How long is a star balanced? 1 M star ~ 10 Billion yrs (our Sun) Know this one M = One Solar Mass (Our Sun’s Mass) 16 M star ~ 200 M yrs 100 M star ~ 3 M yrs Massive Star Life Massive star Lots of gravity Needs lots of fusion Burns fuel fast Massive star lives hard and fast More massive star shorter life Fusion FUSION IN STAR: • Powers the star • loses mass, emits energy • Balances the star • fusion and gravity • Lighter elements combine to make heavier elements • Sun-like stars: He, Li, (Be, B, C) • Heavier stars: He, C, O, Si …Fe Summary • Gravity pulls in • Energy from fusion pushes out • Star (alive) is balanced • Fusion: lighter elements heavier elements + energy • E = mc2 (mass converted to energy) • Less massive star – long lived • Massive star – short lived, because it MAKES HEAVY ELEMENTS Star Life Summary SHORTEST LIFE and LARGEST MASS • • • • Supergiants – shortest lives; ~3–50 million years Giants – shorter lives; ~100 million years Main Sequence – long lives; billions of years White & Red Dwarfs – longest lives; hundreds of billions of years or trillions of years (maybe to the life of a proton 1032 or more) LONGEST LIFE and SMALLEST MASS KNOW THE ORDER. Don’t need to know numbers. Part 2 Evolution of our Sun From cradle to grave in billions of years Also evolution of other “average” stars (~0.5 M ~3 M) Summary Evolution of our Sun and other average stars 1. 2. 3. 4. 5. 6. Nebula Protostar Main sequence Red giant White dwarf Black dwarf 1. Nebula 1. Nebula • Large gas and dust cloud 2. Protostar • • • • • • Pre-star Formed from contraction of nebula ~30 million years for Sun-like stars More massive star evolves faster 15 M ~ 160 000 years 0.2 M ~ 1 billion years http://apod.nasa.gov/apod/ap130904.html 3. Main sequence star • Most of stars in universe • Fusion powered stars Main Sequence Star Sun Main Sequence Stars Pleides Other Main Sequence Stars Balance cannot go on forever 1 M star ~ 10 Billion yrs 4. Red Giant Sun now Sun as Red Giant In ~ 5 Billion yrs Earth 4. Red Giant • • • • • • Lasts ~1 billion years Core converts H to He H layered above He core Fusion starts in H layer Outer layers expand Strong stellar winds expel outer layers – Hiccups – size changes – Planetary Nebula – gas shell ejected • H He C in core Orbits before Red Giant stage In the meantime, what’s happening to the planets? Orbits at Red Giant stage Giants Ex: Arcturus, Aldebaran, Spica Our star from Earth 4. Red Giant • He exhausted in core (He C) • Carbon core (no more fusion) • Core collapses to degenerate state – white dwarf • Fusion slowing in outer layers • Star gently switching off 5. White Dwarf • Collapsed degenerate core of sun-like star • Lasts 10 to 20 billion years for our sun (~age of universe) Ring Nebula (Planetary Nebula) White Dwarf at center http://apod.nasa.gov/apod/ap060625.html 1500 year intervals 3300 LY away 3 LY across 2300 LY away 18 000 LY away 130 SS wide 15 mi/s 8 000 LY away 6. Black Dwarf • • • • Cooled off dense cinder Older white dwarf None found yet (hypothetical) Few if any exist (universe not old enough) http://apod.nasa.gov/apod/ap990604.html Star Evolution Summary http://www.nasa.gov/pdf/208668main_Planetary_Nebula_Lithograph.pdf Part 3 Supernovas or How some stars go BOOM! Supernova • • • • • Huge explosion of a star Quick (seconds to minutes) Energetic (~200 million suns) Can outshine a galaxy Light fades quickly (weeks) Supernova 1006 http://apod.nasa.gov/apod/ap030328.html Supernova 1994D http://apod.nasa.gov/apod/ap981230.html SN 2004dj www.randybrewer.net M74 Feb 2002 www.rochesterastronomy.orgy.org M101 Aug 2011 Supernova Types • Type I – no hydrogen lines in spectra – Type Ia – white dwarf in binary system explodes – Type Ib – massive star loses outer layers • Type II – have hydrogen lines in spectra from massive star explosion Type 1a supernova • Binary system • One is white dwarf • Mass pulled onto white dwarf – explosion • Used as standard candles to measure large distances – standard candle = known luminosity – billions of light-year distances L Bk 2 D Type II Supernova Massive star explodes Video animation of Crab Supernova explosion and remnant http://www.spacetelescope.org/videos/html/heic0515a.html Type II Supernova • Massive star > ~8 M • Core collapses and explodes because.. • Successive shells of heavier elements in core H He C O Si Fe Type II supernova • • • • H He C O Si Fe Fe is the end of the road Core collapses suddenly (implodes) Rebounds and huge shock wave races outward • Blows up star Supernova Ball Bounce Demostration • NASA Afterschool Universe: Supernova Ball Bounce (1:32) • https://www.youtube.com/watch?v=e-91PbbaKI8 • Stacked Ball Drop by Physics Girl (3:33) • https://www.youtube.com/watch?v=2UHS883_P 60 Supernova remnants (SNR) 1. Rapidly expanding shell of gas 2. Core? SNRs (SuperNova Remants) Vela SNR 800 LY away ~10 000 yrs ago Video http://hubblesite.org/newscenter/archive/relea ses/2007/10/video/a/ X-rays Tycho’s SNR 1572 8000+ LY away 35 LY across http://apod.nasa.gov/apod/ap090317.html SNR 15 000 yrs ago 2600 LY away Importance of SN 1. Standard candles to measure distance 2. Expanding gas (H, He, C, O...Fe) – Enriches gas clouds with heavy elements – Where did heavy elements on Earth come from? • Iron in Iron Range • Meteorite material 3. Shock waves can trigger star formation 4. Massive explosion produces even heavier elements (beyond iron) 5. We are made of star stuff! Star Stuff • “The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff.” • Carl Sagan famously said in his 1980 series Cosmos. Strange Parts of SN • Type Ia - blows star to bits • Type II - sometimes find core – Some of those are 2 to 3 M squashed into ~10 miles • 1 tsp weighs 100 million tons – Neutron star Type II Supernova Death of a big mass star Super red giant Supergiant Sometimes beam sweeps past Earth and we see… A Pulsar is • A neutron star (small, massive, dense) • With extremely rapid rotation – Slowest: Once every 3 s – Fastest: 716 times/s • And extremely strong magnetic field • That emits precise “signals” • Like a lighthouse beacon Pulsar Jocelyn Bell Puppis A X-rays Neutron star at 600 mi/s IC433, 5000 LY, 65 LY, Blue = radio Red = optical Green = x-ray http://antwrp.gsfc.nasa.gov/apod/ap06 0602.html Crab Nebula 7000 LY 6 LY http://www.spacetelescope.org/news/html/heic0515.html Crab Nebula Supernova history http://www.astronomy.pomona.edu/archeo/outside/chaco/nebula.html Pulsar in Crab Nebula Pulsar Sounds http://www.jb.man.ac.uk/~pulsar/Education/ Sounds/sounds.html OR https://www.youtube.com/watch?v=gb0P6x_ xDEU http://antwrp.gsfc.nasa.gov/apod/ap090216.html http://apod.nasa.gov/apod/ap080617.html Mass of the star determines its fate Supernovas • Exploding stars • Luminous • Types 1a (Binary), Type II (Massive) • Remnants (SNR) – Expanding gas, core • Importance • Neutron stars and pulsars • Black holes next lecture Homework & Updates • • • • Take time to register for fall classes. D2L Quiz 9 & Sun Quiz available No Lab or Lecture on Tuesday, 4/11. No Lab this week. Thursday lab students: Lab Exam 1 on 4/13. Tuesday lab students: Lab Exam 1 on 4/18. • Observations: Star Gazing, Telescopes & Moon Craters (60 pt.) • (Tonight) April 6, Thursday, Jackson Middle School, Champlin, MN • April 7, Friday, Bell Museum, University of MN, Minneapolis, MN • Times and directions on class website • Observation Option: Univ. of MN Public Lectures – Only Do 1! • Thur, Apr 20, 7pm, Ted Mann Concert Hall, A Deeper Understanding of the Universe from 1.2 miles Underground (find Raquel for 10 points). No credit given if you went to the lecture on 4/4/17.