lect 15 part 1

lect 15 part 1 - 3/24/2010 Exam 2 Based on Lectures notes,...

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3/24/2010 1 Exam 2 • Based on Lectures notes, problems worked on class, and quizzes (Chapters/sections 17.6-22.??) • To be held at Testing Center (basement of Science and Tech 1 building , see attached map). • You may take the exam anytime during the days 3/29 – 4/3 Please check hours of operation at http://ttc gmu edu/hours htm Depends on what it is covered on Thursday • You need to bring a Picture ID, pen/pencil (calculators are not allowed, but you can use the Windows calculator). • Exam will be administered via Blackboard system. • Approximately 50 questions. • There will be a quiz on the material covered until Thursday and that is due at 3:00 pm on 3/30. • On 3/30,I will review (including quiz 7). • There is class on Thursday April 1 st . http://ttc.gmu.edu/hours.html Testing Center (basement of Science and Johnson Center Lecture room at Enterprise Hall Tech 1 Building) Pulsars gradually slow down as they radiate energy into space • The pulse rate of many pulsars is slowing down steadily • This reflects the gradual slowing of the neutron star’s rotation as it radiates energy into space star s rotation as it radiates energy into space • Old Pulsars: slowed down to a period of a second or more • In Summary: An isolated pulsar slows down as it ages, so it’s pulse period increases but some pulsars can speed up!
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3/24/2010 2 Sudden speedups of the pulse rate are called glitches Superfluidity and superconductivity are among the strange properties of neutron stars • A neutron star consists of a superfluid, superconducting core surrounded by a superfluid mantle and a thin, brittle crus crust • Glitches may be caused by interactions between the neutron star’s crust and its superfluid interior or material falling onto the crust. • There is evidence for an “atmosphere” Evidence for an atmosphere
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3 Evidence for an atmosphere => absorption of X-rays photons The fastest pulsars were probably created by mass transfer in close binary systems • They are called millisecond pulsars (period between 1- 10ms) (or 100-1000 rotations per second) • If a neutron star is in a close binary system with an ordinary star, tidal forces will draw gas from the ordinary star onto the neutron star • How do we know is a close binary system? Short orbital periods, 10-100 days (remember Kepler’s third law) • The transfer of material onto the neutron star can make it rotate extremely rapidly, giving rise to a millisecond pulsar In a binary system formed by a high-mass and a Low-mass star: - The high-mass star will become a Type II supernovae; neutron star. Then the pulsar will slow down radiating energy. - The low-mass star (slowly evolving) becomes later a red giant and starts to spill gas over to the neutron star, increasing its rotational speed. But, not all millisecond pulsars are members of close binaries…
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This note was uploaded on 02/06/2011 for the course ASTR 113 taught by Professor Geller during the Spring '08 term at George Mason.

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lect 15 part 1 - 3/24/2010 Exam 2 Based on Lectures notes,...

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