P8.3.1-2

Question 1

What do we use as evidence to say that galaxies are moving away?

Answer 1

Red shift

Question 2

What is red shift?

Answer 2

• Our universe is expanding, as an galaxy moves further away in space, the wavelength increases and frequency decreases.
• Since the wavelength is longer, the light coming from the galaxies is shifted towards the red end of the spectrum, giving off a red light.

Question 3

If a galaxy is moving away from us and its distance is increasing, is it going faster or slower?

Answer 3

Faster

Question 4

How did our universe start?

Answer 4

With the big bang

• All matter occupied a single point
• Exploded
• Space started expanding and is still expanding.

Question 5

What other evidence is there for the big bang?

Answer 5

• Microwave radiation is coming form all direction
• This is leftover from the Big Bang
• Called Cosmic Microwave Background Radiation (CMBR)
• This energy has stretched overtime to be equivalent to the microwave region of the electromagnetic spectrum.

Question 6

What does our solar system comprise of?

Answer 6

Sun
Planets
Moons (natural satellites)
Minor Planets (e.g. dwarf planets like Pluto, asteroids)
Comets
Artificial satellites

Question 7

What are the 4 inner planets?

Answer 7

Mercury, Venus, Earth and Mars

Question 8

What are the atmospheres on Venus, Mars and Mercury like?

Answer 8

On Mars and Mercury the atmosphere is thin.

On Venus the atmosphere is made of mainly CO2 and it rains sulphuric acid.

Question 9

What are the 4 outer planets?

Answer 9

Jupiter, Saturn, Uranus and Neptune

Question 10

What are Jupiter and Saturn known as?

Answer 10

The gas giants

Question 11

What are Uranus and Neptune known as?

Answer 11

The ice giants

Question 12

What is the asteroid belt?

Answer 12

• It is between Mars and Jupiter
• Asteroids are bits of rock left over from the formation of the Solar System.
• Also has a dwarf planet called Ceres.

Question 13

How was the sun formed?

Answer 13

• Formed from a huge cloud of hydrogen
• Gravity pulled the gas and dust together and the central core got very hot
• Particles were moving fast enough and nuclear fusion occured

Question 14

Describe the life cycle of a star up to a main sequence star.

Answer 14

• Clouds of gas and dust are brought together by gravity
• Spiral together and form a prostar
• Temperature increases as the star gets denser as particles collide more often with greater force
• When the temperature is high enough hydrogen nuclei undergo nuclear fusion giving out lots of energy forming a star.

Question 15

Describe the characteristics of a main sequence star.

Answer 15

• A main sequence star is at a period of equilibrium
• Energy released by fusion gives an outward pressure, this is balanced by the force of gravity pulling everything inwards.
• Lasts billions of years

Question 16

What is gravitational collapse?

Answer 16

Gravity pulling everything inwards.

Question 17

After a main sequence star is formed, what can be formed?

Answer 17

Red giant or red supergiant

• Hydrogen in the core runs out and fusion of heavier elements occur. Star swells up and turns red as the surface coosl
• Small to medium sized stars (e.g. Sun), form red giants
• Bigger stars form Red Supergiants - they glow brightly as more fusion occurs and they expand and contract several times.

Question 18

What happens when a red giant runs out of fuel for fusion?

Answer 18

• It becomes unstable and ejects its outer layer of dust and gas in the form of a planetary nebula.
• Leaving behind a dense solid core called a white dwarf which eventually cools and fades away.

Question 19

What happens to red supergiants when they run out of fuel?

Answer 19

• They collapse into themselves and have a massive explosion called the supernova.

Question 20

What does the supernova do?

Answer 20

• Throws layers of gas and dust into space, leaving a dense core called a neutron star
• If the neutron star is big enough it will become a black hole - super dense point in space that even light can’t escape from it.