ASTR 1346 1st Edition Lecture 12 Outline of Last Lecture I Mass Ranges A Low Mass Stars II Core Contraction III Electron Degeneracy IV Helium Flares and Carbon Core V Planetary Nebula Stage Outline of Current Lecture I Einstein s Relativity A Length Contraction B Time dilation C Relativistic Mass II Neutron Star III Black Holes A Escape Speed IV Schwarzschild Radius and Event Horizon Current Lecture l Einstein s relativity talks about curved space Mass distorts spacetime causing it to curve Gravity can be described as the motion or attraction caused by the curvature of spacetime The more mass the more curve A Length contraction is when the length of an object decreases as its speed increases B Time dilation is when time slows down at higher speeds At the speed of light time will be zero C Relativistic mass is when mass increases with speed At the speed of light mass becomes infinite ll These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute If the mass of a neutron star increases more than 3 solar masses the neutron degeneracy pressure can no longer stand against gravity the remnant core collapses even further and it becomes a black hole lll We cannot see a black hole because the escape speed in the black hole is greater than the speed of light Density is so high that even light cannot escape A star collapses to a point where density is infinite and the radius is zero which is called a singularity A Escape speed is the speed needed for an object to escape from the gravitational pull of another Escape speed is proportional to the square root of mass divided by the radius Even light cannot escape now from the surface of the Earth it will become a black hole lV The critical radius at which the escape speed from an object would equal the speed of light is called the Schwarzschild radius Rs Radius is proportional to the mass of an object The imaginary surface of a black hole at Rs within which no event can ever be seen heard or known by anyone outside is called the event horizon These are not physical boundaries just communication barriers With increasing mass Rs would grow but not the physical radius