Cosmology

Question 1

What are the 3 Laws of Kepler?

Answer 1

The orbits are ellipses, equal areas are swept out in equal time intervals, T^2 is proportional to r^3

Question 2

What is a satellite?

Answer 2

an object in orbit around another

Question 3

First three stages of a star forming?

Answer 3

Nebula - cloud of dust and gas, Protostar - critical temp. fusion starts, Main Sequence

Question 4

Last three stages of a small star?

Answer 4

Red Giant - core collapse, shell burning, White Dwarf - layers drift off, hot core, Black Dwarf - cools, invisible

Question 5

Last three stages of a massive star?

Answer 5

Red Supergiant - layers of fusion until core made of iron, Supernova, Neutron star/black hole

Question 6

What holds a white dwarf together?

Answer 6

Electron degeneracy pressure

Question 7

What holds main sequence star together?

Answer 7

Gravity inwards, gas and radiation pressure outwards

Question 8

What holds a neutron star together?

Answer 8

Neutron degeneracy pressure

Question 9

What is the Chandrasekar Limit?

Answer 9

The max mass that electron degeneracy pressure can prevent the collapse of - 1.44Mo

Question 10

What is the event horizon?

Answer 10

boundary of black hole where the escape velocity is greater than the speed of light

Question 11

What is the Schwarzchild radius?

Answer 11

The distance from the singularity of a black hole to the event horizon

Question 12

What is luminosity?

Answer 12

The total radiant power output of a star

Question 13

Why are emission spectra better than absorption?

Answer 13

Some lines may be missing from the absorption spectrum because electrons may deexcite indirectly.

Question 14

How do absorption spectra work?

Answer 14

Photons bombard electrons cooler gas, causing them to excite. The electrons deexcite, and scatter photons which do not reach the sensor, causing a black line spectrum.

Question 15

Why are telescopes better than eyes?

Answer 15

wider aperture collects more light and is less similar to the wavelength of light = less diffraction = less image distortion

Question 16

What is a black body?

Answer 16

a perfect emitter and absorbs all EM radiation

Question 17

What is the Stefan-Boltzmann law?

Answer 17

total power radiated per unit surface area of a black body is directly proportional to temperature^4

Question 18

How old is our universe?

Answer 18

Approx. 13.5 billion years

Question 19

Steady State Theory

Answer 19

Matter is created continuously

Question 20

How many light years is a parsec?

Answer 20

3.26

Question 21

What is 1AU?

Answer 21

1.5x10^15m

Question 22

What is a parsec?

Answer 22

The distance at which the radius of 1AU subtends the angle of an arcsecond.

Question 23

What is recessional velocity?

Answer 23

The speed at which a galaxy is moving away from another

Question 24

What is the cosmological principle?

Answer 24

universe is isotropic and homogeneous when viewed on a large scale

Question 25

What does isotropic mean?

Answer 25

universe looks the same in all directions, no centre or edge to it

Question 26

What does homogeneous mean?

Answer 26

matter is evenly distributed - no preferred location, density is constant

Question 27

What are the universal laws?

Answer 27

theories and models of physics tested on Earth can be applied to the whole universe

Question 28

What is the evidence supporting the Big Bang?

Answer 28

red shift shows galaxies are accelerating away, temperature and CMB matches expected cooling, 2.7K, spectrum matches a black body, relative abundance of light elements (H and He)

Question 29

How is CMB evidence for the Big Bang?

Answer 29

shows that when matter and radiation were strongly coupled, universe was isotropic and homogeneous, temp at 2.7K, expected

Question 30

Properties of CMB radiation?

Answer 30

isotropic, temp of 2.7K, black body spectrum

Question 31

How was CMB radiation formed?

Answer 31

Early universe hot, matter and radiation in thermal equilibrium,