Brainscape's Knowledge GenomeTM

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


See full index

A level physics > 19 - Stars > Flashcards

19 - Stars Flashcards

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

What is a planet?

A

An object in orbit around a star with three important characteristics:

  • mass large enough for its own gravity to give it a round shape
  • no fusion reactions
  • cleared its orbit of most other objects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the difference between an asteroid and a planet?

A

Planets are round due to their gravity whereas asteroids are irregularly shaped

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

What is the difference between a planet and a dwarf planet?

A

Dwarf planets have not cleared their orbit of other objects.

e.g Pluto has many objects of a similar size to it in its orbit

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

What is an asteroid?

A

A small uneven object which orbits the sun

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

What is a comet?

A

Small irregular bodies made up of ice, dust and rock which orbit the sun in elliptical orbit.

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

What happens when a comet approaches the sun?

A

They develop bright tails

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

What is the difference between an asteroid and a comet?

A

Asteroids have a circular orbit around the sun but comets have an elliptical orbit.

Comets contain ice but asteroids do not.

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

What is a solar system?

A

A sun and all the objects that orbit it.,

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

What is a galaxy?

A

A collection of stars, dust and gas.

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

What is the average number of stars that a galaxy contains?

A

100 billlion

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

What is our galaxy called?

A

The Milky W`ay

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

What is a nebula?

A

Gigantic clouds of dust and gas

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

What is the main gas that makes up nebulae?

A

Hydrogen

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

How big are nebulae?

A

100s of times the size of our solar system

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

What is a protostar?

A

A very hot and dense sphere of dust and gas which is not a star.

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

What is nuclear fusion?

A

A process where two smaller nuclei join together to form one larger nucleus.

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

Where is nuclear fusion most commonly found?

A

Stars

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

What does a low mass star become after its main sequence?

A

Red giants

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

What does a high pass star become after its main sequence?

A

Red supergiant

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

Describe the lifecycle of a low mass star

A
  • Main Sequence
  • Fusion stops and star collapses in on itself
  • Fusion begins in outer shell
  • Red Giant
  • Fusion stops in outer shell
  • Outer layers float away
  • Planetary nebula with white dwarf at centre
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is electron degeneracy pressure?

A

The pressure exerted by fast moving electrons which prevents core collapse up to the Chandrasekhar limit.

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

What is the Chandrasekhar liit>

A

1.44 M⊙ (Solar Mass)

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

What are the boundaries for the mass of a low mass star?

A

0.5M⊙ < M < 10M⊙

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

Why does fusion stop in the core of a star?

A

Because it runs out of hydrogen.

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

Why do low mass stars not carry out fusion with elements heavier than hydrogen?

A

Because they do not have enough pressure or high enough temperature to fuse elements heavier than hydrogen.

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

Why do white dwarf stars not collapse further?

A

Because of electron degeneracy pressure.

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

What are the boundaries for a high mass star?

A

M > 10M⊙

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

Describe th4e life cycle of a high mass star.

A
  • Main sequence
  • Fusion stops in core and star collapses in on itself
  • Pressure and temperature are enough to begin helium fusion in core
  • Radiation pressure increases in core so star swells
  • Super red giant (fusion in shells)
  • Helium runs out in core and star collapses again
  • Fusion of carbon begins in core
  • Cycle continues until star has a core of iron
  • Fusion cannot occur in iron so gravity causes the star to collapse
  • Shells bounce off core in a massive explosion - SUPERNOVA
  • Either neutron star or black hole
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What causes a neutron star to form after a supernova?

A

If the mass of the star is less than 3M⊙ (but greater than Chandrasekhar limit.

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

What causes a black hole to form after a supernova?

A

If the mass of the star is greater than 3M⊙

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

What stars last for longer on their main sequence?

A

Low mass stars

32
Q

What is a neutron star?

A

A very small star made up of just neutrons with a mass of about 2M⊙ and a very high density, close to the density of an atomic nucleus.

33
Q

What is a black hole?

A

If the mass of the star before supernova was greater than 3M⊙ then it continues to compress down into a singularity with a gravitational field so strong not even photons can escape it.

34
Q

Where are all the elements in the universe made?

A

Stars

35
Q

How are elements heavier than iron produced?

A

In a supernova, all elements are created.

36
Q

What is stellar (solar) luminosity?

A

The total radiant power output of the star.

37
Q

What is the unit of solar luminosity?

A

L⊙

1L⊙ = 3.85x10^26

38
Q

Compare the surface temperatures of different types of stars.

A
  • Red (Super) Giant = cool
  • Main Sequence = hotter
  • White dwarf = hottest
39
Q

Compare the luminosity of different types of stars.

A
  • Red supergiant = most luminous
  • Red giant = more luminous
  • Main sequence = luminous
  • White dwarf = least luminous
40
Q

Why are electron energy levels said to be discrete?

A

Because they can only exist with a specific amount of energy.

No electron can exist between these energy levels

41
Q

Why are energy levels of electrons always negative?

A

Because external energy is required to escape an electric field (see electric fields)

42
Q

How much energy does an electron that is free from an atom have?

A

0 energy

43
Q

What is the electron level with the most negative value known as?

A

Ground state

44
Q

What is it called when external energy is applied to an electron to raise it to a higher energy level?

A

Exciting

45
Q

How could an electron be excited?

A

Heating

Photons being absorbed

46
Q

What happens when an electron moves down an energy level?

A

It releases energy - a photon with the specific energy that the electron has lost

47
Q

Does each element have the same energy levels?

A

No - each element has unique energy levels

48
Q

What equations can we use to calculate energy of a photon?

A

ΔE = hf

ΔE = hc / λ

49
Q

What is emission line spectra?

A

Each element produces a unique emission lie spectrum because of its unique set of energy levels

50
Q

What is a continuous spectra?

A

All visible frequencies / wavelengths are present. For example a lamp filament would produce this type of spectrum

51
Q

What is an absorption line spectra?

A

Series of dark spectral lines against the background of a continuous spectrum.

52
Q

What do the spectral lines of an absorbtion line spectra have a wavelength equal to?

A

The wavelengths of the emission line spectrum for the same gas atoms.

53
Q

How does an absorbtion spectra form?

A

Light from a continuous spectra source passes through a cooler gas.

Some photons of specific wavelengths are absorbed, raising the electrons in the gasses to a higher energy level.

A lack of photons for certain frequencies produces dark spectral lines, a negative image of the emmision spectra for the gas the light passed through.

54
Q

How can we use absorbtion spectra to analyse starlight?

A

We can look at an absorbtion spectra from a star and match the spectral lines against an emission spectra to see which elements are in the star.

55
Q

Why do we use a diffraction grating instead of a double slit to split light up?

A

Because it produces a brighter and clearer pattern - more light passes through.

56
Q

What is the path difference at the zero order maximum?

A

0

57
Q

What is the grating equation?

A

d sinθ = nλ

58
Q

What is d in the grating equation?

A

The distance between the slits in the grating

59
Q

What is n in the grating equation?

A

The maxima number

60
Q

What is λ in the grating equation?

A

The wavelength of the light passing through the grating.

61
Q

What is θ in the grating equation?

A

The angle between the grating and the direction of the light.

62
Q

What is the largest possible angle that θ can be and why?

A

90 degrees because sin 90 = 1

63
Q

How do you calculate the highest order maxima?

A

n(max) = d/ λ

64
Q

What is a black body?

A

An object that emits electromagnetic radiation in a continuous spectrum across all wavelengths.

65
Q

What is the peak wavelength of a black body?

A

The most intense wavelength that the object emits.

66
Q

How does the temperature of an object affect the peak wavelength?

A

The peak wavelength is smaller for hotter objects.

67
Q

What is Wein’s displacement law?

A

λₘₐₓ ∝ 1 / T

Peak wavelength is directly proportional to 1 over the surface temperature of the black body

68
Q

What can Wein’s displacement law be applied to?

A

Most objects from mammals to stars

69
Q

What is Stefan’s law?

A

L = 4πr²σT⁴

70
Q

What does Stefan’s law tell us?

A

Luminosity is directly proportional to:

Radius (L ∝ r²)
Surface Area (L ∝ 4πr²)
Surface temperature (L ∝ T⁴)
71
Q

What is σ in Stefan’s law?

A

Stefan’s constant

5.67 x10⁻⁸ W m⁻² K ⁻⁴

72
Q

What can be calculated by combining Wien’s Law and Stefan’s law.

A

The radius of a distant star can be estimated.

73
Q

What is a white dwarf?

A

A small very dense star that is typically the size of a planet. They are very hot.

74
Q

What has a shorter wavelength, blue or red light?

A

Blue light.

75
Q

What colour light is closer to the central central maxima when it is diffracted.

A

Blue light is closer to the central maxima

Red light is further.

A level physics (26 decks)

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