Lecture 20 - Neutron Stars and Black Holes

Lecture 20 - Neutron Stars and Black Holes - Neutron Stars...

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Neutron Stars and Black Holes ASTRONOMY 3 Lesson 20 1 The central pulsar in the crab nebula observed in X-rays and the visual.
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NATURE of the Universe Review of Lesson 19 Astronomy - Neutron Stars & Black Holes • Once all the hydrogen in its core has been fused into helium, the Sun will become a red giant. Subsequent fusion results in a carbon core. • At the end of the red giant phase, the Sun will have lost almost half of its mass by winds. It will end as a carbon white dwarf. • Stars more massive than the Sun gain energy by nuclear fusion leading up to iron. • All elements on Earth apart from hydrogen have been produced in the interiors of stars and in the course of supernova explosions. 2
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NATURE of the Universe Questions from Lesson 19 Astronomy - Neutron Stars & Black Holes Think about (questions from Lesson 19): • Can anything be denser than a white dwarf? • Can anything travel faster than light? 3
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• Neutron stars and Pulsars (Ch. 13.1 - 13.3) • Einstein’s theories of relativity (Ch. 13.6, 13.7) • Black Holes (Ch. 13.5, 13.8) NATURE of the Universe Today’s Topics Astronomy - Neutron Stars & Black Holes 4
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NATURE of the Universe Astronomy - Neutron Stars & Black Holes - + Hydrogen Helium A little bit more nuclear physics. .. Atoms consist of a core (nucleus) orbited by electrons. The nucleus consists of neutrons and positively charged protons In the core of a star, electrons and nucleus get separated and move around freely. proton electron In a white dwarf, pressure created by the electrons counteracts gravity and prevents further collapse. 5
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If the pressure gets too high, a proton and an electron can combine to form a neutron. This removes the electron pressure, and the core can collapse until only neutrons are left. - + + proton electron neutron NATURE of the Universe Astronomy - Neutron Stars & Black Holes The core of a massive (8 to 25 times the mass of the Sun) star supernova does not turn into a white dwarf. It becomes a neutron star. SciAm 6
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Size comparison of a neutron star and the Los Angeles basin NATURE of the Universe Astronomy - Neutron Stars & Black Holes 70 km 10 km A neutron star has 1 to 3 times the mass of the Sun compressed to a sphere with 10 km diameter 7 See http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=8277
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Astronomy - Neutron Stars & Black Holes A neutron star has 1 to 3 times the mass of the Sun Let’s zoom in on the neutron star in the center of the crab nebula (the massive star supernova from 1054) Combined visual and X-ray view. 10 light years
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This note was uploaded on 10/13/2008 for the course ASTR 3 taught by Professor Hauser during the Fall '07 term at UCLA.

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Lecture 20 - Neutron Stars and Black Holes - Neutron Stars...

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