Lecture_16

Lecture_16 - What would it be like to visit a black hole?...

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1 What would it be like to visit a What would it be like to visit a black hole? black hole? If the Sun shrank in size to a Black Hole of equal mass , its gravity would be different only very near the Event Horizon (3 km from center). The radius of the Sun is ~700,000 km! A black hole of 1 Msun is a small object . There would be no change in Earth’s orbit. Black holes don’t suck objects in! They are not vacuum cleaners. Light waves take extra time to climb out of a deep hole in spacetime leading to a gravitational redshift of the light. Rubber sheet represents the fabric of spacetime. Matter warps or stretches the fabric of spacetime The warping of spacetime implies that time itself passes more slowly near the Event Horizon.
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2 TIDAL FORCES (the difference in the gravitational force across an object due to the inverse square law) near the Event Horizon of a 3 M Sun Black Hole would be lethal to humans. Tidal forces would actually be much gentler near a supermassive black hole because its radius is much bigger . Stronger gravitational force Weaker gravitational force Black Hole Verification Need to measure mass Use orbital properties of companion Measure velocity and distance of orbiting gas It’s a black hole if it’s not a star and its implied mass exceeds the neutron star limit (~3 M Sun ) One famous X-ray binary with a likely black hole is in the constellation Cygnus; it is called Cygnus X-1. Our Galaxy Our Galaxy • Our Goals for Learning • What does our galaxy look like? • How do stars orbit in our galaxy? All sky view
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3 The Milky Way galaxy appears in our sky as a faint band of light. A GALAXY is a huge conglomeration of billions of stars. The Sun is a member of one such galaxy, our galaxy, also known as the Milky Way. Dusty gas clouds obscure our view because they absorb visible light. This is the interstellar medium that makes new star systems. We see our galaxy edge-on but from the inside. Primary features: very flat “disk” of stars, a central bulge of stars, a large spherical halo with some stars, and a spherical distribution of globular clusters. The Sun lies 28,000 lightyears from the center. If we could view the Milky Way from above the
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This note was uploaded on 02/20/2012 for the course ASTRO 3 taught by Professor Mclean during the Spring '11 term at UCLA.

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Lecture_16 - What would it be like to visit a black hole?...

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