P7 - Astronomy

Question 1

A star of a much greater mass than the sun will eventually become

Answer 1

a black hole

Question 2

describe how the sun reached its main sequence stage

Answer 2

• a nebula
• which collapsed and came together under gravity
• transferred to thermal energy and begins to glow and forms protostar
• into hot enough to star nuclear fusion

Question 3

suggest why knowing the age of the oldest star is not enough to tell scientists the age of the Universe

Answer 3

• the oldest star had not yet appeared when the big bang happened
• the universe is older than the oldest star
• stars take time to form

Question 4

Explain what red shift is and how it provides evidence that the Universe is expanding (6)

Answer 4

• it is when light is shifted to the red end of the spectrum
• light waves are stretched so wavelength increases and has a short frequency
• spectral lines move to the red end
• a decrease in frequency means the source is moving away
• if wavelength is people longest at red end = shortest frequency = short frequency = moving away
• red shift shows galaxies are moving away from us
• further away = greater red shift
• Doppler Effect : as wavelength increases, frequency decreases

Question 5

explain why red shift supports both theories (Big Bang and Steady State Theory) but CMBR supports only one of them

Answer 5

• both theories predict expanding universe and Big Bang also predicts universe had a beginning
• red shift indicates universe is expanding so supports both theories
• whereas CMBR also indicates that the universe had a beginning so supports Big Bang and disproves Steady State

Question 6

Describe the significance of microwave radiation in the development of a theory of the origin of the universe

Answer 6

• discovery of cosmic background radiation
• could be explained as a result of the big bang theory
• cannot be explained by steady state theory

Question 7

Stars may originate as a nebula

Describe the process that then occurs to produce the conditions necessary for nuclear fusion in a star

Answer 7

• nebula collapses
• under gravity
• and very high temperatures are reached

Question 8

describe what happens to the frequency and wavelength when the dolphin stops swimming

Answer 8

• frequency is lower

- wavelength is longer

Question 9

describe how you could use this fact to measure the time it takes for the Earth to orbit the sun once

Answer 9

• start the clock when the sun is at its highest

- finish clock when sun is at highest again

Question 10

state how the brightness of a main sequence star changes with its temperature

Answer 10

• the greater the temperature, the higher the brightness

Question 11

state how the brightness of a main sequence star changes with its mass

Answer 11

• the greater the mass the higher the brightness

Question 12

explain why the evidence available at the time supported the geocentric model

Answer 12

• at the time there was only naked eye evidence
• which indicated sun and moon moved across the sky
• in the same direction and motion everyday

Question 13

which row is correct for both force and velocity

Answer 13

D - Vector Vector

Question 14

describe what is meant by red shift

Answer 14

• increase of wavelength and decrease of frequency

- as a star moves away from us

Question 15

what does the M in CMB radiation stand for

Answer 15

Microwave

Question 16

state what is meant by cosmic background radiation

Answer 16

• radiation that comes from all over space and the universe

Question 17

explain how the presence of CMBR provides evidence for the big bang theory

Answer 17

• the big bang theory has a beginning/ initial explosion

- that released radiation identified at CMBR