Exam 3

Question 1

Massive star supernova

Answer 1

Iron core of massive star reaches white dwarf limit and collapses into a neutron star, causing explosion

Question 2

White dwarf supernova

Answer 2

Carbon fusion suddenly begins as white dwarf in close binary system reaches white dwarf limit, causing total explosion (this one is smaller than the massive star supernova) quickly, in the period of a few weeks

Question 3

Supernovae are much more ____ than nova

Answer 3

Luminous. 10 million times!

Question 4

Nova

Answer 4

H to He fusion of a layer, white dwarf left intact. For hydrogen fusion, you need 10 million K. (in a binary star system)

Question 5

Supernova

Answer 5

Complete explosion, nothing left behind except for a neutron star or black hole.

Question 6

How do you distinguish between massive star and white dwarf supernova?

Answer 6

1) Light curves differ 2) Spectra differ

Question 7

Light curve

Answer 7

??? One is a day earlier.??? CHECK SLIDE.

Question 8

Spectrum

Answer 8

Exploding white dwarfs don’t have hydrogen absorption lines. No lines corresponding with carbon, helium, hydrogen.Type 1A only one that comes from white dwarf exploding. What is Type II?

Question 9

Type 1B

Answer 9

Doesn’t have the hydrogen around it.

Question 10

Type 1C

Answer 10

Both hydrogen and helium were removed from the star.

Question 11

Main-sequence mass –> redgiant or super giant (depending on whether or not you are above 8 Solar Mass –> white dwarf, neutron star/black hole (latter based on 25 Solar Mass and above)

Answer 11

SEE SLIDE FOR HELPFUL DIAGRAM

Question 12

Neutron degeneracy pressure can’t hold it together, you become _____ _____

Answer 12

Black hole

Question 13

What happens when things go really fast or get really big?

Answer 13

velocity increases, length decreases and mass increases, time decreases.

Question 14

Length contraction

Answer 14

As you move closer to the speed of light, moving objects appear shorter to the observers

Question 15

Time dilation

Answer 15

Time passes more slowly on moving objects than on stationary objects

Question 16

The masses of moving objects increase as their speeds approach c

Answer 16

look at formula on slide

Question 17

If v = c,

Answer 17

infinite mass, time = 0

Question 18

Special relativity

Answer 18

Deals with things that travel very fast

Question 19

General relativity

Answer 19

Space can expand faster than the speed of light. but nothing can travel faster than the speed of light. during inflation, our universe went from size of atom to size of solar system

Question 20

General relativity

Answer 20

describes matter accelerating at high rates or in the presence of great matters

Question 21

Is there a difference between acceleration due to gravity or due to actual motion

Answer 21

effects are the same. since acc depends on spatial position and time, then the acceleration caused by gravity must mean that mass affects perception of space and time

Question 22

We live in a 4D world of ___

Answer 22

Spacetime

Question 23

Mass curves the shape of

Answer 23

Spacetime. greater masses concentrated in smaller areas gives greater curvatures

Question 24

In spacetime, acceleration can be due to motion through space or a response to

Answer 24

curvature in spacetime

Question 25

Prediction: curved space

Answer 25

Confirmed using solar eclipse.

Question 26

Position of the star was different after six months

Answer 26

apparent position of the star 6 months earlier actual position of star was different. in presence of big masses, spacetime is curved

Question 27

The sun is not massive is not to distort the image of the of something - bend the light alot

Answer 27

quasar in the middle of two images

Question 28

How do we know that two objects in the sky are the same

Answer 28

light spectrum is identical

Question 29

Black hole can also bend the light and split an image into two (because black hole is massive enough)

Answer 29

see slide

Question 30

2nd proof of relativity:

Answer 30

gravitational lensing

Question 31

Gravitational lensing

Answer 31

effect of distortion of space, the image is stretched. massive object in the background (simulated with a lens) becomes distorted. can become a ring if it is directly in front of line of sight. Cluster of galaxies in front behaves like a lens, so if it was too far away to see before, we can see them now because the photons are reaching us. the light is converged towards us.

Question 32

Look more further away from us

Answer 32

we see closer to the beginning of the universe (big bang)

Question 33

What happens to the escape velocity from an object if you shrink it?

Answer 33

It increases

Question 34

Schwarzchild radius

Answer 34

how big where even light cannot escape R=2GM/C^2

Question 35

Singularity

Answer 35

in the black hole and in the big bang. things tending towards zero. we know what happened up to 10^-43 seconds of the universe starting. gravity crushes all matter into a single point known as singularity

Question 36

Singularity --> S radius --> event horizon

Answer 36

Schwarzchild radius keeps us from seeing singularity regularity - nature abhors singularity

Question 37

Do black holes really exist? Even light can't escape, so how can we know?

Answer 37

Very bright and variable x ray source associated with a Blue Supergiant. The star is not hot enough to make X rays.

Question 38

Black hole in a binary system

Answer 38

black hole accretes matter from star. the matter is super heated as it falls into black hole. could not have been made by neutron star

Question 39

Supermassive black hole

Answer 39

formed from massive star that died. several million times the size of the sun

Question 40

Black hole at the center of the milky way

Answer 40

kepler's 3rd law to determine the mass of the object the star is orbiting. mass = 4 million solar masses. very big but cant see it. many galaxies have them. relation between mass of galaxy and size of black hole at the center.

Question 41

Density equation for black hole

Answer 41

see slide

Question 42

Evaporating Black Hole

Answer 42

Hawking radiation