1Bizarre Stellar GraveyardCuriouser and Curiouser1Friday, November 18, 111Bizarre Stellar GraveyardCuriouser and Curiouser1Friday, November 18, 112Learning goals: be able to ...• Contrast a massive-star supernova with a white-dwarf supernova. • State the difference between a pulsar and a neutron star, from our perspective. • Contrast Newton’s concept of gravity with that of Einstein’ space-time• Define black hole and what is meant by the event horizon.• Explain what is meant by the gravitational redshift• Outline the differences between reference frames for an object falling into a black hole: what the observer “sees” versus what happens to the object (see textbook, p. 570 - 571)• State what determines whether what is left of a star becomes a white dwarf, a neutron star, or a black hole. (see text)2Friday, November 18, 113• Contrast a massive-star supernova (Type II) with a white-dwarf supernova (Type Ia).Massive Star (Type II) supernovahttp://www.youtube.com/watch?v=5YZkAoR3WLEWhite dwarf (Type Ia) supernovahttp://www.youtube.com/watch?NR=1&v=j7Y0uRsMrh43Friday, November 18, 11Massive star supernovae come from stars that have fused to iron in their cores and experience a core collapse. Isolated stars.White dwarf supernovae come from stars in a binary system where one star - the more massive one - has evolved to a white dwarf. These stars are close enough together that when the other star evolves to the red giant stage, its large atmosphere gets drawn to the white dwarf. The white dwarf accumulates the gas until the limit is surpassed and it blasts itself to pieces.4How can we tell the difference?White dwarf supernovae (Type Ia) are good standard candles for finding distances. Each one comes from objects that are nearly identical and are formed under nearly identical ways. Get the luminosity of one and you have that of all of them. Use equation - get distance.4Friday, November 18, 11Identical in that each comes from a white dwarf that has a maximum mass limit, and an average mass of around 70% that of the Sun. The process is similar in that the white dwarf is feeding off of material from a companion red dwarf that is losing mass to the white dwarf.What do we mean by a standard candle?5Neutron Star•White dwarf limit is 1.4 times the mass of the Sun•If remnant is more massive than ~1.4 solar masses -- electron degeneracy cannot provide support•Core collapses into a neutron star; neutron degeneracy provides support• State the difference between a pulsar and a neutron star, from our perspective.5Friday, November 18, 11Structure of a neutron star66Friday, November 18, 117Most famous pulsar:The Crab PulsarConstellation Taurus (the bull)HyadesAldebaran7Friday, November 18, 11While Europe was deep within the dark ages, the Chinese astronomers were observing the sky. The record of this supernova – the one that became Messier 1 and the Crab nebula – was set down in Chinese record. The neutron star at the center is also a pulsar. If you were to take a spectrum of the reddish-purplish wisps of gas you would get an emission spectrum. A spectrum of the grayish central region would reveal a continuous spectrum produced by electrons spiraling in a magnetic field, synchrotron radiation.About 6300 lightyears away.7Most famous pulsar:The Crab PulsarConstellation Taurus (the bull)HyadesAldebaran7Friday, November 18, 11While Europe was deep within the dark ages, the Chinese astronomers were observing the sky. The record of this supernova – the one that became Messier 1 and the Crab nebula – was set down in Chinese record. The neutron star at the center is also a pulsar. If you were to take a spectrum of the reddish-purplish wisps of gas you would get an emission spectrum. A spectrum of the grayish central region would reveal a continuous spectrum produced by electrons spiraling in a magnetic field, synchrotron radiation.About 6300 lightyears away.8• State the difference between a pulsar and a neutron star, from our perspective.8Friday, November 18, 118• State the difference between a pulsar and a neutron star, from our perspective.8Friday, November 18, 118• State the difference between a pulsar and a neutron star, from our perspective.8Friday, November 18, 119• State the difference between a pulsar and a neutron star, from our perspective.A pulsar is a rotating neutron star thatbeams radiation along its magnetic axis.If magnetic axis is not aligned with rotationaxis, pulsar beams sweep through space likelighthouse beams.9Friday, November 18, 11Neutron star seen as a pulsar from our perspective10Friday, November 18, 1111http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.htmlConservation of angular momentum means these creatures spin extremely fast! Millisecond pulsars (1000 times per second)11Friday, November 18, 11vhttp://www.gb.nrao.edu/~glangsto/pulsars/47tuc1-8000.wavhttp://www.jb.man.ac.uk/~pulsar/Education/Sounds/47tuc2-8000.wavhttp://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.html11http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.htmlConservation of angular momentum means these creatures spin extremely fast! Millisecond pulsars (1000 times per second)11Friday, November 18, 11vhttp://www.gb.nrao.edu/~glangsto/pulsars/47tuc1-8000.wavhttp://www.jb.man.ac.uk/~pulsar/Education/Sounds/47tuc2-8000.wavhttp://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.html11http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.htmlConservation of angular momentum means these creatures spin extremely fast! Millisecond pulsars (1000 times per second)What is the significance of finding aneutron star in a globular cluster?11Friday, November 18, 11vhttp://www.gb.nrao.edu/~glangsto/pulsars/47tuc1-8000.wavhttp://www.jb.man.ac.uk/~pulsar/Education/Sounds/47tuc2-8000.wavhttp://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.html12All pulsars are neutron stars, but not all neutron stars are pulsars.Theoretically, what is a pulsar?Observationally, what is a pulsar?What are the characteristics of a neutron star ? How do we know these objects aren’t just white dwarfs?Neutron Stars and PulsarsIf neutron degeneracy can't provide support....12Friday, November 18, 11What are the characteristics of a neutron star ? How do we know these objects aren’t just white dwarfs?A Black Hole ResultsAnimation of Black Hole Formation in SN 1979C13Friday, November 18, 1114Einstein: Space and time are one; the presence of mass warps spacetime.Newton’s
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