Ast 105 1nd Edition Lecture 13 Outline of Previous Lecture I. Death of starsII. AGB starsIII. White DwarfIV. Electron Degeneracy PressureV. Chandra Sakhar VI. NovaVII. Roche LimitVIII. Low and High Mass stars Outline of Current Lecture I. Super NovaII. Neutron Stars III. Pulsar’sIV. Binary Neutron Star SystemsV. X-ray Bursters Current LectureSuper Nova- Chandrasekhar limit is exceeded: electrons+protons neutrons and neutrinos - Core density = 1017 kg/m3 Nuclear density - Neutron core is stable- Outer regions collapse due to gravity - Matter rebounds off the neutron core Core bounce- Shock wave travels outward, away from core This blasts away the rest of the star - This blast is called a super nova- A supernova increases the luminosity by 100 million times. - Many types of the heavy elements are created except platinum gold and silver- The death of a high mass star produces a type 2 supernova. Type two contains balmer series in spectra- Another type of supernova is the type 1a. These begin as a binary with a white dwarf and a giant Spectra has no balmer series Giant is inside the Roché limit, mass builds up on the white dwarf eventually C.S limit is exceeded type 1 a is a supernovaNeutron Star“garbage disposal of the universe”- main sequence stars with masses greater than 8 Msun (less than 25 Msun) explode as a supernova leftover is what we call the neutron star- 1.4 Msun to about 3 Msun - neutron star = giant nucleus mostly all neutrons- density = 1017 kg/m3 nuclear density - one teaspoon of neutron star matter weighs 1 billion tons- Neutron stars have a radius of about 10 km, which is approximately 6 miles- Escape velocity of a neutron star is one half the speed of light- Acceleration due to gravityPulsar’s - Neutron stars must have high spin rates due to the conservation of angular momentum- Stars have strong magnetic field- the larger the omega the faster it is turning- pulsar=neutron star high spin rate strong magnetic field - spinning magnetic field periodic radio signal Binary Neutron Star Systems- It is not possible for the supernova to create all elements- If we have a binary of 2 neutron stars in orbit, they decay, collide produce the heavier elementsX-ray Burster - Neutron stars with a main sequence will produce a burst of x-rays- Gravity pulled onto neutron star is fused to form helium helium heats up helium fuses this produces x-rays x-ray burster - binary w/ a N-5 + Main
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