Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics P7 > 7.4 - The Sun, stars and surroundings > Flashcards

7.4 - The Sun, stars and surroundings Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What do all objects emit?

A

A continuous range of electromagnetic radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The _____ the object, the ____ radiation it emits.

A

The HOTTER the object, the MORE radiation it emits.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does the colour and luminosity of a star depend on?

A

Its surface temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where in the star is the density and temperature the highest?

A

Core

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How hot is the Sun’s core?

A

16 million C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What takes place in the core?

A

Nuclear fusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What do nuclear reactions release? What happens after?

A

Photons are released which travel outwards through the star, transferring energy as radiation through the RADIATION ZONE.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is the energy transferred on the surface of a star?

A

Convection currents

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where is energy radiated into space from?

A

Photosphere (surface of a star)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a line spectrum?

A

Where there are just a few coloured lines at specific wavelengths.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two types of spectra?

A

Emission and absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is emission spectrum?

A

If a gas is heated and the spectrum viewed through a prism it does not give a continuous spectrum but a line spectrum specific to the gas being heated.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is absorption spectrum?

A

When white light is shone through the gas, some of the continuous spectrum is absorbed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What can we determine when studying these dark lines?

A

The chemical composition of a star.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is ionisation?

A

When a photon is absorbed by an atom the energy may be enough to remove an electron from the atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

By looking at which ions are present, what can we determine?

A

How energetic the absorbed photons are and this gives an indication of the temperature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does line spectra indicate in terms of electrons?

A

Electrons in an atom do not have a continuous range of energy otherwise the spectra would be continuous.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do electrons in an atom exist?

A

In specific energy levels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When an electron drops from one energy level to the other, what happens?

A

A photon of light is emitted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How can temperature be described?

A

How concentrated the thermal energy is.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

The _____ the temperature of something the______ its molecules move.

A

The HIGHER the temperature of something the FASTER its molecules move.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

As molecules move faster, what is gained?

A

Kinetic Energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does the temperature of gas depend on?

A

The average Kinetic Energy of the molecules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is Absolute Zero?

A

The coldest possible temperature - the point where molecules would stop moving altogether.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How cold is Absolute Zero?

A

-273 C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

As the temperature of a gas increases the molecules move faster, causing the gas to ______ and take up ____ space.

A

As the temperature of a gas increases the molecules move faster, causing the gas to EXPAND and take up MORE space.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What would the result look like if a graph was plotted of temperature against volume?

A

A straight line graph which when extrapolated backwards, reaches a point where volume is ZERO at -273 C.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Starting the temperature scale at -273 shows that volume is ____________ to absolute temperature (in Kelvin).

A

Starting the temperature scale at -273 shows that volume is DIRECTLY PROPORTIONAL to absolute temperature (in Kelvin).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How would you convert Kelvin into Celsius?

A

SUBTRACT 273.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How would you convert Celsius into Kelvin?

A

ADD 273.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

If volume was kept fixed, what would happen to pressure (against temperature) ?

A

Reducing temperature would mean the particles hit the wall of the container less often until eventually the molecules are not moving and pressure falls to ZERO.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What would the result look like if a graph was plotted of temperature against pressure?

A

A straight line graph which when extrapolated backwards, reaches a point where pressure is ZERO at -273 C. PRESSURE IS DIRECTLY PROPORTIONAL TO TEMPERATURE.

33
Q

If a piston was filled with gas, what would the effect of pressure be if volume is reduced?

A

INCREASES PRESSURE.

34
Q

What would the effect of pressure be if volume is increased?

A

REDUCE PRESSURE.

35
Q

What is pressure in a gas actually caused by?

A

Gas molecules hitting the sides of a container.

36
Q

What is Boyle’s Law?

A

Constant = Pressure x Volume

37
Q

What does Boyle’s law explain?

A

As long as temperature and mass stay the same, if the pressure increases the volume must decrease and vice versa.

38
Q

What kind of graph would be represented by Boyle’s Law?

A

An INVERSELY PROPORTIONAL graph.

39
Q

What is an ‘ideal gas’ ?

A

One with well separated molecules that do not affect each other. A gas well above its boiling point and not under high pressure will behave as an ideal gas.

40
Q

What is the combined gas law formula?

A

(pressure x volume) / temperature = constant

41
Q

What does Boyle’s Law show?

A

INVERSE PROPORTIONALITY - Doubling one variable halves the other.

42
Q

What does “pressure/temperature = constant and volume/temperature = constant” show?

A

DIRECT PROPORTIONALITY - doubling one variable doubles the other.

43
Q

What is nebulae?

A

Immense clouds of molecular gas.

44
Q

What does nebula mainly contain?

A

Hydrogen, helium, interstellar dust.

45
Q

How is a star born?

A
  1. Gravity slowly pulls the gas and dust together.
  2. As the cloud collapses GPE is transferred into KE, the particles move faster and temperature increases.
  3. Clumps of nebulae collapse into denser regions that eventually become stars.
  4. Denser regions remain stable while the outward pressure is balanced by the inward gravitational attraction.
  5. The temperature becomes so hot it glows red. This is a protostar.
  6. Over the next few million years, the protostar’s gravity attracts more and more material to it.
  7. The more material it attracts the more massive it becomes and the stronger its gravitational attraction. This attracts more material.
  8. Eventually, the core becomes so hot and dense that nuclear fusion begins and a new star is born.
46
Q

What did Einstein’s theory of relativity explain?

A

How matter could be converted into energy and how the huge mass of the Sun is slowly being converted to Energy.

47
Q

What is the Sun powered by?

A

Nuclear fusion.

48
Q

How does nuclear fusion work?

A

Hydrogen nuclei fusing together to form helium and releases huge amounts of energy in the process.

49
Q

How much energy does our Sun produce in Fusion?

A

3x10^26 Joules per second.

50
Q

How does nuclear fusion take place?

A

In a series of reactions called the P-P cycle.

51
Q

How do we represent the nucleus?

A

In the form of A/Z X where
A = Mass Number
Z = Atomic Number
X = Chemical symbol

52
Q

How is the reaction of two protons fusing together written as?

A

1 1 H + 1 1 H –> 2 1 H + 0 +1 e + 0 0 V

e = Positron
v = Neutrino
53
Q

In each of the reactions, what happens to the mass number? What happens to the mass between the products and the reactants? What happens to the missing mass?

A

The mass number is conserved but mass is not. The total mass of the products is slightly less than the total mass of the reactants. The missing mass has been converted into energy.

54
Q

What is Einstein’s energy equation called?

A 
E = mc^2
(E) = Energy
(m) = Mass lost
(c) = Speed of light in a vaccum
55
Q

How much mass is the Sun losing per second?

A

10^38 reactions per second in the Sun = 3x10^9 kg lost per second

56
Q

What type of star is the Sun?

A

A Main Sequence Star.

57
Q

What happens during the Main Sequence?

A

Hydrogen is being fused into helium in the core. The outward pressure due to gas and radiation is balanced by the inward force of gravity.

58
Q

In larger stars, what do they have the ability to do?

A

The core temperatures and pressures are so high that they can form heavier elements.

59
Q

What will Helium Nuclei fuse into?

A

Beryllium, Carbon and Oxygen. If the temperature is high enough it will continue up to iron - the maximum element that can be produced.

60
Q

What is the link between the mass of the elements and releasing of energy?

A

Fusing lighter elements releases energy but to form elements heavier than iron requires energy to be provided.

61
Q

Once the core stops releasing energy, what happens?

A

The forces are no longer balanced and gravity will begin to crush the star.

62
Q

What does the Hertzsprung-Russell diagram show?

A

The difference between a star’s luminosity and temperature.

63
Q

What is plotted on the axises of the Hertzsprung-Russell Diagram?

A

y-axis = Luminosity

x- axis = Surface Temperature (K) INCREASES FROM RIGHT TO LEFT.

64
Q

What do Main Sequences form on the Hertzsprung-Russell diagram?

A

A diagonal line across the centre of the diagram.

65
Q

Where are Giants and Supergiants placed on the diagram?

A

To the top right of the diagram.

66
Q

Where are White Dwarfs placed on the diagram?

A

The bottom left.

67
Q

As a star runs out of hydrogen, what happens?

A

Fusion is reduced, less energy is produced and pressure drops. Gravitational attraction can then crush the star.

68
Q

After the star runs out of hydrogen, how does its shape/structure change?

A

It’s mainly helium surrounded by a shell of hydrogen.

69
Q

What happens as the star collapses?

A

Density and temperature increase once more and fusion begins again. The energy released by this causes the star to expand enormously and the photosphere cools as it expands and the star becomes a red giant/supergiant.

70
Q

When a star is so hot after producing helium what happens?

A

Helium begins to fuse into beryllium and then carbon.

71
Q

Briefly describe the life stage of a low mass star.

A
  1. When they become a red giant, they don’t have the mass to compress the core further at the end of helium fusion.
  2. At this stage, fusion stops, the core collapses and the outer layers are ejected into space. The remnant is a white dwarf star surrounded by a planetary nebula.
  3. The white dwarf eventually will cool into a black dwarf.
72
Q

Briefly describe the life stage of a large-mass star.

A

They do not end with helium fusion. These supergiants have enough mass that the gravity is able to fuse heavier elements. Carbon, nitrogen and oxygen and all elements up to and including iron are formed.

73
Q

What happens when the core is mostly iron?

A

Further fusion absorbs energy rather than releasing it. The star cannot generate any more energy so there is nothing opposing the gravitational attraction.

74
Q

What happens once the star is not opposing the gravitational attraction?

A

The star collapses into a supernova.

The heaviest elements are formed during collapse which ends when the star explodes scattering material across space and leaving behind a small extremely dense core called the NEUTRON STAR.

If a star is VERY large the core is so dense it will turn into a BLACK HOLE.

75
Q

What are three reasons as to why finding planets around different stars is difficult?

A
  1. They are too small to see at such a distance.
  2. They don’t give out their own light.
  3. Light reflected from them is lost in the glare from the star.
76
Q

When looking for extra-solar planets, what must astronomers study?

A

The star itself and look for signs of the effect an orbiting planet has on the star.

77
Q

What are the two methods used when looking for extra-solar planets?

A
  1. Wobble Method: As a planet orbits a star the star is also attracted to the planet. Because the star is so much more massive than the planet the star does not move much but wobbles enough that astronomers can detect tiny changes to its position/colour of its light caused by the DOPPLER EFFECT.
  2. Transit Method: As a planet passes in front of a star it blocks a tiny amount of the light from the star so that the star’s apparent brightness changes in a regular way as the planet orbits.
78
Q

What is the Goldilocks zone?

A

A region around a star thought to be habitable.

Neither too hot nor too cold and in a position where water would be liquid.

79
Q

What are 3 places where scientists are looking to identify a Goldilocks zone?

A
  1. Mars: Evidence suggest there was liquid water. May have rocks and fossils.
  2. Europa (Jupiter’s Moon): Has a frozen surface and liquid water oceans MAY exist below but no evidence.
  3. SETI (Search for Extraterrestrial Intelligence): A project that listens for radio signals from space. Nothing major found yet.

Physics P7 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions