Topic 7 - Astronomy

Question 1

Describe the Steady State theory

Answer 1

The Steady State theory says that the universe has always existed but is expanding and creating matter to counteract the loss in density.

Question 2

Describe the Big Bang theory

Answer 2

The Big Bang theory states that the universe expanded from a very small dense point about 14 billion years ago.

Question 3

What is red-shift?

Answer 3

A perceived increase in the wavelength of light due to the source moving away from the observer.

Question 4

What does red-shift provide evidence for?

Answer 4

● The universe is expanding

● This supports the Big Bang theory

Question 5

What does the Big Bang theory suggest?

Answer 5

The entire universe started from a very small, hot and dense region in space.

Question 6

Compare the observed red-shift of two galaxies, one further away than the other.

Answer 6

The galaxy that is further away is travelling faster

● The observed red-shift is greater the further away it is

Question 7

What did scientists observe to provide evidence that the universe is expanding at an ever faster rate?

Answer 7

They observed supernovae, which suggested that galaxies are moving away at an ever faster rate.

Question 8

Prior to observations of supernovae, what was believed about the rate of expansion of the universe and why?

Answer 8

● The rate of expansion was expected to occur more slowly

● It was thought that gravitational forces would cause this slowing down

Question 9

What does CMBR stand for?

Answer 9

Cosmic Microwave Background Radiation

Question 10

What does CMBR provide further evidence for?

Answer 10

The Big Bang Theory
It is believed that CMBR originates
from radiation produced in the Big Bang

Question 11

How does the existence of CMBR support the expansion of the universe?

Answer 11

It is thought that gamma radiation was released in the Big Bang
The expansion of the universe has stretched this radiation, resulting in the microwave radiation present today

Question 12

What factor determines the type of lifecycle a star undergoes?

Answer 12

The size of the star.

Question 13

What do stars like the sun become at the end of their life-cycle?

Answer 13

A black dwarf.

Question 14

What two things can stars much bigger than the sun become at the end of their lifecycle?

Answer 14

1. Neutron star

2. Black hole

Question 15

What two phases do stars of similar size to the sun go through between being a main sequence star and a black dwarf?

Answer 15

1. Red giant

2. White dwarf

Question 16

What two phases do stars of greater size than the sun go through between being a main sequence star and a neutron star/black hole?

Answer 16

1. Red supergiant

2. Supernova

Question 17

Describe the transition of the star from the nebula stage to the main sequence.

Answer 17

●The nebula increases in size until it is pulled in due to its gravity, causing GPE to turn into KE
● The collisions between particles cause this kinetic energy to turn into thermal energy
● Eventually the nebula will become dense and hot enough to begin fusion

Question 18

What occurs in the stage when a star is a main sequence star?

Answer 18

● The fusion in the star releases energy
● This energy balances out with the gravitational
potential energy leaving the star
● The star is in equilibrium so will not collapse
due to gravity or expand due to radioactive behavior. It is stable.

Question 19

What happens when a star transitions to the red giant stage?

Answer 19

● Once all of the hydrogen fuel has been used up, the star begins to fuse helium and other
larger nuclei
● This causes the star to expand and become a
red giant

Question 20

How does a red giant become a white dwarf?

Answer 20

● Once all reactions have taken place, the star’s gravity pulls in all of its mass, making a small,
dense white dwarf
● This will cool down to form a black dwarf

Question 21

Why are telescopes located outside the earth’s atmosphere?

Answer 21

● The earth’s atmosphere absorbs many electromagnetic waves, making it difficult to detect certain waves.
● Light pollution can make some images less clear
● Telescopes in space can operate both night and day

Question 22

What is the disadvantage of telescopes located outside the atmosphere?

Answer 22

They are difficult to maintain as they have to be repaired in space (or brought down, which is unreasonably expensive)

Question 23

What are the disadvantages of optical telescopes?

Answer 23

● They can only be used at night when the sky is clear

● They can’t be used when the weather is cloudy etc.

Question 24

Evaluate the use of radio telescopes.

Answer 24

● They are not weather dependent for example radio waves are not blocked by clouds so can
be used in the rain
● They are usually large and expensi