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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
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
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
EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 26 Core of > 3Msun after massive
star supernova will collapse into
oblivion. These exotic dance teams
spiral toward each other in
spiral toward each other in
an orbital decay, emitting
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 Newton’s law of gravity no longer valid!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 http://astroblob.blogspot.com/ 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.
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- Fall '13