Black holes and general relativity

black holes

a region of space where gravity is so powerful that not even light can escape it

what is the event horizon?

the spherical surface of a black hole that increases with the mass of the hole

If you observe something moving near light speed, relative to you____

its time (clock) slows down, its length contracts in direction of motion, and mass increases

Spacetime

a combination of time and space intervals between two events

Gravity

spacetime geometry

Equivalence principle

A free-falling observer experiences the same phenomena as a free observer in the absence of gravity. the laws of nature are the same for both

Geometry on curved surface

Straight lines are the shortest paths between two points in a flat space. Great circles are the shortest paths between two points on a sphere.

What curves space-time?

Mass of sun

What is gravitational lensing?

Curved spacetime alters the paths of light rays, shifting the apparent positions of objects in effect called gravitational lensing

spacetime tells matter and energy ___

how to curve

matter and energy tell spacetime ____

how to curve

wormholes

a hypothetical tunnel connecting two different regions in spacetime

Gamma-ray bursts

among the most powerful explosions in universe

What is the life cycle of a low mass star?

1. protostar 2. main-sequence 3. red giant 4. Helium burning star 5. double shell burning star 6. planetary nebula 7. white dwarf

what is the common trait of all main-sequence stars?

they generate energy through hydrogen fusion in their core

The sun will exhaust its nuclear fuel in about

5 billion years

What star has the largest radius in the galaxy?

red supergiants

You observe a star, and you want to plot it on an HR Diagram. You will need to measure all of the following, except the star’s

mass. (need spectral type, distance, brightness)

The approximate main-sequence lifetime of a star of 30 solar masses is

3 million years