Astronomy (7)

Question 1

What are the steady state and big bang theories?

Answer 1

Steady state:
The idea that the universe has always existed. As it expands, new matter is constantly being created. There is also no end to the universe.
Big bang theory:
All the universe was concentrated in a very small space (very dense and hot). It then exploded and is still expanding. The age of the universe is finite.

Question 2

What is evidence for the big bang theory?

Answer 2

Red shift:
Different elements absorb different frequencies of light producing a pattern of dark lines on the visible spectrum. When we look at light from distant galaxies, we see the same patterns but at lower frequencies (shifted to the red end of the spectrum). This is an observed increase in wavelength as the waves get ‘stretched’. It shows that the universe is expanding as the galaxies move further away from us.
Cosmic Microwave Background Radiation (CMBR):
Low frequency EM radiation all around the universe due to high levels of radiation released when the big bang occured.

Question 3

Evolution of stars with a similar mass to our sun.

Answer 3

Nebula:
Cloud of dust and gas.
Protostar:
Force of gravity pulls dust and gas together. Temperature rises and the star becomes denser to the point where nuclear fusion occurs, forming helium nuclei. This gives out huge amounts of energy which keeps the core hot.
Main sequence star:
A long stable period where outward pressure of thermal expansion = force of gravity.
Red giant:
Hydrogen in the core begins to run out and force of gravity > force of thermal expansion. The star is compressed until fusion can occur again where the outer layers expand.
White dwarf:
The star becomes unstable and ejects outer layers of dust and gas leaving behind a hot, dense, solid core.

Question 4

How is evolution different for larger stars?

Answer 4

Main sequence star:
This stage lasts less.
Red supergiant:
A red giant but larger.
Supernova:
Stars start to glow brightly as they undergo fusion to make heavier elements (up to iron). The balance shifts several times until the star explodes into a supernova.
Neutron star or black hole:
The explosion throws outer layers of dust and gas into space leaving a very dense core called a neutron star. If the star is big enough, it will collapse into a black hole.

Question 5

How have methods of observing the universe changed?

Answer 5

Some telescopes are located outside of the Earth’s atmosphere so that they are not affected by things like light pollution, weather or time of day.