unit eight: astrophysics

Question 1

orbit

Answer 1

the gravitationally curved path of an object around a point in space

Question 2

perihelion

Answer 2

the point in orbit closest to the sun

Question 3

aphelion

Answer 3

the point in orbit furthest from the sun

Question 4

orbital speed =

Answer 4

(2 x π x orbital radius) / time period

Question 5

circumference of a circle

Answer 5

2 x π x r

Question 6

gravitational field strength of earth

Answer 6

10 N/kg

Question 7

gravitational field strength of the moon

Answer 7

1.6 N/kg

Question 8

first stage of a star life cycle

Answer 8

stellar nebula

Question 9

what is the star life cycle for a high mass star

Answer 9

1. high mass star
2. red supergiant
3. supernova where matter and energy are…
4. flung into space
5. neutron star
6. black hole

Question 10

what is the life cycle of a low mass star

Answer 10

1. low mass star
2. protostar
3. red giant
4. white dwarf
5. black dwarf

Question 11

how many stars are in the milky way

Answer 11

100-400 billion

Question 12

how wide is the milky way

Answer 12

105,700 light years

Question 13

what is the temperature of the suns core

Answer 13

15 million Kelvin/celsius

Question 14

what is the distance from the sun to earth

Answer 14

150 million km

Question 15

what is the temperature of the suns surface

Answer 15

6000 Kelvin

Question 16

what surface temperature is an O classed star

Answer 16

more than 33,000K

Question 17

what colour is an O classed star

Answer 17

blue

Question 18

what surface temperature is a B classed star

Answer 18

33,000 - 10,000K

Question 19

what colour is a B classed star

Answer 19

blue - white

Question 20

what surface temperature is a A classed star

Answer 20

10,000 - 7500K

Question 21

what colour is a A classed star

Answer 21

white

Question 22

what surface temperature is a F classed star

Answer 22

7500-6000K

Question 23

what colour is a F classed star

Answer 23

yellow - white

Question 24

what surface temperature is a G classed star

Answer 24

6000 - 5200K

Question 25

what colour is a G classed star

Answer 25

yellow

Question 26

what surface temperature is a K classed star

Answer 26

5200 - 3700K

Question 27

what colour is a K classed star

Answer 27

orange

Question 28

what surface temperature is a M classed star

Answer 28

3700 - 2000K

Question 29

what colour is a M classed star

Answer 29

red

Question 30

what is the variable displayed on the vertical axis of the Hertzsprung-Russell Diagram

Answer 30

absolute magnitude (m)

Question 31

what are the three main sections of a Hertzsprung Russell Diagram

Answer 31

supergiants, main sequence and white dwarfs

Question 32

how are planets and moons visible

Answer 32

they reflect light from the sun

Question 33

how does the sun release vast amounts of energy

Answer 33

it is fuelled by a continuous nuclear reaction

Question 34

what are comets

Answer 34

relatively small objects consisting of rock and ice

Question 35

what does gravitational force depend on

Answer 35

size of masses involved, and distance between the masses.

Question 36

if size of mass increases, then the force of gravity

Answer 36

increases

Question 37

if the distance between masses increases, then the force of gravity

Answer 37

decreases

Question 38

what is apparent brightness/apparent magnitude

Answer 38

a measure of how bright the star appears from the Earth

Question 39

what does the apparent brightness depend on

Answer 39

what the star is made from and the kinds of nuclear reactions taking place, and the distance the star is from Earth

Question 40

what is the absolute brightness/absolute magnitude

Answer 40

a measure of how bright the star would appear if they were all placed the same distance (10 parsecs) from the Earth

Question 41

what is the luminosity

Answer 41

a measure of the amount of light energy emitted from the stars surface every second

Question 42

how do nuclear fusions begin in stars

Answer 42

hydrogen nuclei join to make larger nuclei and huge amounts of energy are released as heat and light

Question 43

when is a star stable

Answer 43

when the high temperatures and pressures generated to try and push the star apart generate an outward force in the star, but it is balanced with gravity providing an inward force that tries to push the particles together

Question 44

how does a star become a red giant

Answer 44

as the hydrogen runs out, frequency of collisions decreases and the rate of hydrogen fusion decreases. the gravitational forces are now dominant and begin to compress the star and temperatures reach the point where fusion reactions can occur between helium nuclei.

Question 45

how does a star become a white dwarf

Answer 45

the helium runs out, but further fusion reactions take place to produce larger nuclei. the gravitational forces cause the star to collapse inwards, increasing its core temperature even more

Question 46

when does a star become a neutron star (life cycle)

Answer 46

if the remaining core after the supernova is less than 3 times the mass of the sun

Question 47

when does a star become a black hole

Answer 47

if the remaining core after the supernova is more than 3 times the mass of the sun.

Question 48

if a light source is moving, describe the movement of the light waves

Answer 48

the wavefronts will no longer be equally spaced, and the ones ahead of the light source will be compressed and have a shorter wavelength, meaning they will have a higher frequency and be blue. ones behind the light source will be stretched out, have a longer wave length and be red.

Question 49

how fast does electromagnetic radiation travel?

Answer 49

300 million m/s

Question 50

light from galaxies moving towards us leads to a

Answer 50

blueshift

Question 51

light from galaxies moving away from us leads to a

Answer 51

redshift

Question 52

what do you need to know to measure how fast the galaxies go

Answer 52

how large the redshift or blueshift is

Question 53

if we see a redshift, that means the universe is expanding, meaning

Answer 53

at some point in the past all the matter in the universe was condensed in a single point which it expanded from

Question 54

what is cosmic microwave background radiation

Answer 54

during the big bang a lot of high energy cosmic rays would have been produced. as the universe has expanded the space the waves have travelled through has also expanded. this has increased their wavelength and have gradually moved through the EM spectrum to become microwaves. they can be detected from all directions supporting the idea that all matter and energy originated at one point

Question 55

how long ago was the big bang

Answer 55

13.7 billion years ago

Question 56

change of wavelength / wavelength =

Answer 56

velocity of galaxy / speed of light

Question 57

what is the symbol for wavelength

Answer 57

λ

Question 58

how would you calculate change of wavelength

Answer 58

final wavelength - inital wavelength

Question 59

what is the speed of light

Answer 59

3 x 10 to the power of 8