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IGCSE Physics > Chapter 6: Space Physics (Pt. 2) > Flashcards

Chapter 6: Space Physics (Pt. 2) Flashcards

1
Q

What is the Sun?

A

An average or medium mass star

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2
Q

What is the Sun made up of?

A

about 75% hydrogen
about 24% helium
the rest (1%) is made up of other elements like oxygen and carbon.

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3
Q

How does the Sun radiate energy?

A

The glowing hydrogen at the surface of the Sun radiates energy

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4
Q

Tell me about the types of energy the Sun radiates.

A

40% of the energy is visible light
50% is infrared radiation
10% is ultraviolet

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5
Q

How does the Earth absorb the ultraviolet radiation?

A

The Earth’s atmosphere absorbs a lot of this ultraviolet radiation.
The ozone layer, in particular, absorbs most of the harmful (more ionising) ultraviolet.

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6
Q

What are stars powered by?

A

Nuclear reactions that release energy.

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7
Q

What are stable stars powered by?

A

Stable stars, like our Sun are powered by the nuclear fusion of hydrogen into helium.
This makes the Sun shine

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8
Q

Tell me about the reactions within the Sun.

A

As it is so hot inside the Sun, matter exists as plasma (positive ions and electrons)
Although the Sun produces gamma rays due to the nuclear fusion process, collisions with the plasma mean that it takes about 100 000 years for that energy to reach the Sun’s surface.
In addition, because the energy is spread over a big surface (photosphere) the temperature is lower at the Sun’s surface compared to the core.

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9
Q

Define galaxy.

A

A huge collection of gas, dust and billions of stars and their solar systems held together by gravity.

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10
Q

What galaxy is our Sun a part of?

A

the Milky Way Galaxy.

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11
Q

Why is the Milky Way called the Milky Way?

A

Because it appears as a milky band of light in the sky when you see it in a really dark area.

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12
Q

Where are the stars that we see in the night sky from?

A

The Milky Way

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13
Q

Define light-year.

A

A measure of distance (not time). It is the distance that light travels through space in one year.

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14
Q

At what speed does light travel in a vacuum?

A

3 x 10^8 m/s

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15
Q

The time light takes to travel somewhere is ______________.

A

directly proportional to distance.

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16
Q

What is one light year?

A

9.5 x 10^15 m.

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17
Q

The distance between stars is __________.

A

much bigger than the size of each solar system.

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18
Q

What is the next nearest star after the Sun?

A

Proxima Centauri which is about 4.2 light years away

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19
Q

Tell me the life cycle of a star.

A
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20
Q

What does the life cycle of stars begin with?

A

A cloud of dust and gas in outer space called a nebula

21
Q

What is a nebula made up of?

A

The nebula is mostly made up of hydrogen

22
Q

How is a protostar formed?

A

Over time, gravity pulls the fragments of gas and dust together, forming a hot ball of gas called a protostar.

23
Q

How does the protostar become more dense?

A

As more particles collide and join the protostar, it gets larger in size, which increases the force of gravity. The increase in gravity attracts more dust and gas, but also makes the protostar denser.

24
Q

How does nuclear fusion take place in protostars?

A

The particles inside start to collide more often and more frequently, which raises the temperature of the protostar.
When the temperature gets high enough, hydrogen nuclei start fusing together to form helium nuclei.
We call this process nuclear fusion.

25
Q

How is the core of the star kept hot?

A

Nuclear fusion releases a large amount of energy and this constant release of energy keeps the core of the star hot.

26
Q

How does a star remain stable?

A

The outward pressure, caused by the high temperature and release of energy, is balanced by the force of gravity. This allows stars to remain stable for billions of years. At this point, we call the star a main sequence star.

27
Q

What stage of the lifecycle of a star is our Sun at?

A

A main sequence star

28
Q

How does a red giant form?

A
  1. The star runs out of hydrogen eventually, which no longer fuels the nuclear fusion reactions
  2. The inward force of gravity takes over and contracts the star into a relatively small ball
  3. Eventually it gets so hot and dense that nuclear fusion takes place again.
  4. At this point, the star also expands again.
  5. This time, the nuclear fusion not only forms helium but also heavier elements.
  6. How much the star expands depends on the size of the original star.
  7. Average sized star: forms a red giant
  8. A massive star: forms a red supergiant
29
Q

Tell me the path of a red giant.

A

planetary nebula –> white dwarf –> black dwarf

30
Q

How is a planetary nebula formed?

A

After the second stage of fusion, the red giant will become unstable.

So, it will eject the outer layer of dust and gas, called a planetary nebula

31
Q

How is a white dwarf formed?

A

Ejecting the planetary nebula forms a hot, dense solid core.

The remaining core is known as a white dwarf as it gives off a lot of light, appearing white.

The white dwarf is relatively small and does not host any nuclear fusion reactions.

32
Q

How is a black dwarf formed?

A

The white dwarf cools down and gets darker as it emits all of its energy.

It eventually becomes a black dwarf.

As it no longer has enough energy to emit light, it appears black.

33
Q

Tell me the path of a red supergiant.

A

red supergiant –> supernova –> neutron star/black hole

34
Q

How is a supernova formed?

A
  1. The super red giant undergoes more nuclear fusion.
  2. After many cycles of expansion and contraction the star collapses and explodes into a supernova.
  3. This forms elements heavier than iron, which are expelled across the universe
35
Q

How is a neutron star formed?

A

When the supernova star condenses into a dense core

36
Q

How is a black hole formed?

A

The supernova star collapses on itself and forms a black hole

37
Q

What does the fate of a supernova star depend on?

A

Its mass.

38
Q

Why are black holes called black holes?

A

Because they are so dense that their gravity is able to pull in any light that gets close.

They appear invisible

Nothing can escape from a black hole, not even light.

39
Q

Tell me the diameter of the milky way.

A

about 100 000 light-years in diameter

40
Q

Explain redshift.

A
  1. An example of the Doppler Effect.
  2. As an object moves away from us, the sound or light waves emitted by the object are stretched out, which maked them have a lower pitch and moves them towards the red end of the electromagnetic spectrum where light has a longer wavelength
41
Q

What is the Big Bang Theory?

A

The widely accepted cosmological model of the origin of the universe.

It describes how the universe expanded from an initial stare of extremely high density and temperature about 13.8 billion years ago

42
Q

What is the proof astronomers have of the Big Bang Theory.

A

The further away a galaxy is, the more red-shifted its light is.

The further away the galaxies are, the faster they are moving.

This is similar to an explosion.

43
Q

What is cosmic background radiation?

A

Electromagnetic radiation from the Big Bang

44
Q

What is Hubble’s law?

A

The speed of the galaxies is directly proportional to the amount of redshift.

45
Q

How is the distance determined In Hubble’s law equation?

A

Using the brightness of a supernova in that galaxy

46
Q

What is the Hubble constant?

A

The gradient, it is the ration of the speed at which galaxies are moving away from Earth to their distance from it.

47
Q
A
48
Q

Tell me the age of the universe.

A

14.3 Billion years

IGCSE Physics (21 decks)

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