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Chapter 14: Black Holes: Matters of Gravity. Special Relativity Time Dilation Length Contraction General Relativity Curved Spacetime Swartzschield Black Holes Kerr Black Holes Worm Holes. Stellar Mass Black Holes Intermediate Range Black Holes Super-massive Black Holes
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Special Relativity Time Dilation Length Contraction General Relativity Curved Spacetime Swartzschield Black Holes Kerr Black Holes Worm Holes Stellar Mass Black Holes Intermediate Range Black Holes Super-massive Black Holes Primordial Black Holes Black Hole X-ray Binaries Black Hole Evaporation and Hawking Radiation Topics Today:
Know the postulates of Special Relativity and the conditions under which they hold. Know how time, length, and mass change with increasing speed. Know how General Relativity interprets gravity. Know how mass affects spacetime. Know the difference between the two basic types of black holes. Know what gravitational radiation is Know the four basic mass ranges for black holes and how/where the corresponding B.H.s are formed. Know the types of observational evidence that would point to the presence of a stellar mass black hole. Know the types of observational evidence that would point to the presence of a super massive black hole. Know what Hawking radiation is. For the Quiz:
Special Relativity, Einstein 1905Postulates: • Your description of physical reality is the same regardless of the velocity at which you move. • Regardless of your speed or direction, you always measure the speed of light to be the same. • Valid for reference frames moving in a straight line at constant speed.
The Speed of Light Is Constant As seen from the ground As seen from the car
By Special Relativity: • Clocks passing by you run more slowly than do clocks at rest. • The mass of an object increases as it moves faster. • The length of an object decreases as its speed increases.
Movement and Space The faster an object moves, the shorter it becomes in its direction of motion as observed by someone not moving with the object.
General Relativity, 1915 • Includes effects of gravity. • Interprets gravity as a curvature of spacetime. • Objects follow the curvature of spacetime. • Light follows the curvature of spacetime.
Curved Spacetime (a) In the absence of any matter in the spacetime, straight lines are straight. (b) In the presence of matter, spacetime curves. (c) This pulls the two masses toward each other.
Gravitational Redshift The photons leaving the vicinity of the massive object lose energy and therefore redshift.
Trapping of Light As the mass increases, so does the curvature of spacetime.
Mass Range of Black Holes • Stellar Remnant - A few solar masses • Supermassive - Millions to billions (centers of most galaxies) • Intermediate Mass – Hundreds to thousands (crowded star clusters) • Primordial – Few grams up to mass of a planet (formed in Big Bang)
LIGO Gravitational Wave Detector Hanford, Washington
Schwarzschild (Nonrotating)Black Hole • A nonrotating black hole has two notable parts: its singularity and its boundary. • Its mass, a singularity, collects at its center. • The boundary between the black hole and the outside universe is called the event horizon. • The distance from the center to the event horizon is the Schwarzschild radius.
Kerr (Rotating) Black Hole • The singularity of a Kerr black hole is located in an infinitely thin ring around the center of the hole. • The event horizon is a spherical surface. • The doughnut-shaped region is called the ergoregion. • Space in the ergoregion is being curved or pulled around by the rotating black hole.
Swirling Space in an Ergoregion Space dragged by a spinning (Kerr) black hole.
Effect of a Black Hole’s Tidal Force Near the Schwarzschild radius, a probe is pulled long and thin by the difference in the gravitational forces felt by its different sides. The probe changes color as its photons undergo extreme gravitational redshift.
Formation of an Accretion Disk Matter pulled toward a black hole spirals inward. Angular momentum of the infalling gas and dust causes it to form an accretion disk around the hole.
Supermassive Black Hole 3-billion solar mass black hole in M87
Accretion Disk Around a Supermassive Black Hole 300-million solar mass black hole in the center of galaxy NGC 7052
Accretion Disk Around a Supermassive Black Hole The gases spiraling inward in an accretion disk heat up as they approach the black hole.
“Intermediate-Mass” Black Hole Central region of M82 from the Chandra X-ray Observatory
Jets Created by a Black Hole in a Binary System Some of the matter spiraling inward in the accretion disk around a black hole is superheated and redirected outward. This produces two powerful jets of particles traveling at close to the speed of light.
Most Powerful Known Gamma Bursts 2704 bursts detected by the Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma-Ray Observatory