Flashcards in Unit 1- Astrophysics Deck (22):

1

## What is the diagram called in which main sequence star's lifetimes are displayed upon?

### hertzsprung Russel diagram

2

## what causes black holes? HINT: not two neutron stars colliding which would happen.

### when a hugely massive star runs out of fuel in the core (All elements turned to iron) and therefore there is an imbalance between the thermal pressure and gravity therefore the star collapses to a point of no volume and creates such a strong gravitational pull that not even light can escape.

3

## what causes neutron stars? And what can they be described as?

### same as black holes except the star stops before compressing to a volume of 0, however it differs from black holes as it is the result of the gravity pushing the electrons inside of the protons and creating neutrons. it can be described as pulsars as it constantly spins at very fast speeds.

4

## what law does gravity abide by?

### the inverse square law.

5

## how do you work out the gravitational field strength of a mass?

### g=Gm/r^2

6

## what is gravitational potential?

### the energy required to move 1kg of mass from infinity to the point in space.

7

## what is a conservative field?

### a gravitational field.

8

## what is escape velocity?

### the velocity required to escape the surface and surpassing gravity.

9

## how do you work out the velocity of a satellite in orbit.

### v=square root of Gm/r

10

## how do you work out the period of a satellite?

### 2π(square root) r^3/Gm

11

## what can we see from the period and velocity equations for satellites?

### that the motions aren't dependant on the mass pf the satellite but instead of the mass in which they are rotating.

12

## what is the equivalence principle?

### accelerating in a rocket is the same as standing in a gravitational field. "you cant tell the difference between the effects of gravity and accelerating"

13

## what are the consequences of the equivalence principle?

### light appears to bend, therefore showing gravitational fields bend light. Also time is effected similarly i.e. time is slower closer to the centre of mass just like the bottom of a rocket.

14

## whats a geodisc?

### moving in a straight line through something curved.

15

## what does mass tell space to do?

### bend

16

## what are the 4 dimensions?

### space and time(future, past and present)

17

## whats the schwarzchild radius?

### the distance between the event horizon and singularity.

18

## whats the event horizon?

### the point at which light cannot escape from a black holes gravitational pull.

19

## how do you work out the schwarzchild radius?

### r = 2Gm/c^2

20

## what is a black body?

### a perfect absorber of energy.

21

## what is hawking radiation?

###
Radiation emitted by a black hole. The radiation is due to the black hole capturing one of a particle-antiparticle pair created spontaneously near to the event horizon.

22