Geometry determines whether we see a pulsar rotate

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Unformatted text preview: ar. rotate pulsar when polar beam sweeps by Earth’s direction once each rotation as fast as 625 s-1 Rotation rate gradually slows as rate gradually slows as neutron star ages. energy & angular momentum carried angular momentum carried away by EM fields created from the continual twirling of magnetic field. no pulsar if polar beam always points toward or away from Earth Crab Pulsar neutron star. nebula pulsar currently rotate at ~ 30 s-1 Neutron star pulsar. EE8086 – Astronomy: Stars, Galaxies & Cosmology we Rotates less than half as fast 2,000 years late. Page 23 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 24 Neutron Neutron Star in Close Binary X-ray Bursters Close binary neutron star also bi steal matter from companion. similar Accreting neutron stars sporadically erupt releasing energy in the form of X-rays – X-ray bursts. This is due to the process; to white dwarf binaries Mass transfer will speed up transfer will speed up spin of pulsar. H-rich material accretes on to the surface of a neutron star forming a layer of H gas; 1 m thick. almost 1,000 s-1 almost 1,000 known as millisecond pulsars pressure high enough for H to fuse steadily on the surface; a layer of He forms underneath He fuses instantly & emits an energy burst when temperatures reach 100m K to Accretion disk becomes hot di enough to emit X-rays. Neutron star “novae” are called X-ray bursters. star novae are called bursters matter releases enormous energy These objects are known as X-ray binaries. objects are known as binaries EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 26 Core of > 3Msun after massive of 3M massive star supernova will collapse into oblivion oblivion. These exotic dance teams spiral toward each other in spiral toward each other in an orbital decay, emitting space space-warping gravity gravity waves. gravity too strong for even neutron degeneracy to stop degeneracy to stop gravity final wins! Star becomes infinitely small. similar to light waves radiating to light waves radiating outward like ripples on a pond creates a “hole” in the universe This is what we call a black hole. Eventually crash & unite. > 3Msun compressed into an infinitely small space has extremely large gravity! Newton’s law of gravity no longer valid! possibly becoming a black hole EE8086 – Astronomy: Stars, Galaxies & Cosmology EE8086 – Astronomy: Stars, Galaxies & Cosmology Black Holes Many neutron-star pairs are now known. each burst has luminosity of 100,000 Suns burst has luminosity of 100 Suns Page 25 Double Neutron Star System burst last a few seconds & repeats every few hours to days infalling Page 27 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 28 Understanding SpaceUnderstanding Space-Time Warping Warping Warping of Space by Gravity Gravity imposes a curvature on spacetime. imposes curvature spacetime Space-time Gravity is the warping of spacetime about an object with is the warping of spacetime an object with mass according to the Theory of Relativity. Theory Even light (no mass) is affected by gravity. li You leave the...
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