Stellar Physics Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is a black body?

A

An ideal black body can absorb and emit all frequencies perfectly. (Stars are NOT ideal black bodies, but we treat them as if they are.)

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

How is the surface temperature of a star related to its peak wavelength?

A

The shorter the peak wavelength, the higher the surface temperature of the star.

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

What are the 7 spectral classes of stars?

A

The spectral classes are: O, B, A, F, G, K and M.

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

How does the colour vary between the spectral classes?

A

(From class O to M) Blue, blue-white, white, yellow-white, yellow, orange, red.

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

How does the mass / radius vary between the spectral classes?

A

From class O to M, the mass / radius decreases.

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

How does the luminosity / surface temperature vary between the spectral classes?

A

From class O to M, the luminosity / surface temperature decreases.

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

How does the lifetime vary between the spectral classes?

A

From class O to M, the lifetime increases.

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

What unit does surface temperature have?

A

Surface temperature is measured in Kelvin, K.

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

What is another word for the luminosity of a star?

A

The luminosity is the power output of a star. (Energy emitted per second)

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

What affects the apparent brightness of a star?

A

The apparent brightness of a star is affected by the luminosity, distance and wavelength distribution of the star.

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

What are Hertzsprung-Russell diagrams?

A

Hertzsprung-Russell diagrams plot the temperature and luminosity of stars.

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

What is the diagonal line on H-R diagrams called?

A

The diagonal line is the Main Sequence.

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

What is the Main Sequence of stars?

A

The Main Sequence contains most of the stars in the universe. These stars are still fusing H -> He. Our sun is in the Main Sequence.

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

What groups are in the top-right of H-R diagrams?

A

Red giants and Red supergiants are found in the top-right of H-R diagrams.

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

What group is in the bottom-left of H-R diagrams?

A

White dwarfs are found in the bottom-left of H-R diagrams.

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

What are red giants/supergiants?

A

Red giants/supergiants are the brightest of all stars, but are colder than most stars. They fuse heavier elements.

17
Q

What are white dwarfs?

A

White dwarfs are some of the hottest stars, but are dimmer than most stars. The don’t fuse anymore elements because they are at the end of the star’s life.

18
Q

How are stars made?

A

Stars are born in huge clouds of dust, called nebula. Gravity pulls gas and dust together, increasing the density. Gravitational potential energy is converted into heat energy, increasing the temperature of the dust and gas. Eventually, the hydrogen has enough energy to undergo fusion, creating the star.

19
Q

What is nebula?

A

Nebula is a huge clouds of spacedust that makes up stars. Nebula is very cold, usually between 10 and 20 Kelvin.

20
Q

What are the 3 stages of a proton-proton chain reaction?

Hint: fusion happens 3 times

A

Stage 1: Two hydrogen nuclei (hydrogen-1) undergo fusion, producing a deuterium nucleus (hydrogen-2), a position and a neutrino. The positron is eliminated by an electron, producing energy in the form of gamma ray photons.

Stage 2: The deuterium nucleus fuses with a proton, producing a helium-3 nucleus and a gamma ray photon.

Stage 3: Two helium-3 nuclei fuse to form a helium-4 nucleus and two free protons, which can go on to start more fusion reactions. This is why it’s a chain reaction.

Summary:
A proton fuses with another proton to form deuterium.
Then deuterium fuses with a proton to form a helium - 3 nucleus.
Two helium - 3 nuclei then fuse to form a helium - 4 nucleus.

21
Q

What happens when a red supergiant stops fusing elements?

A

A supernova is created - a large explosion. This leaves behind either a black hole, or a neutron star (a high density small star, made almost entirely of neutrons)

22
Q

What happens when a red giant stops fusing elements?

A

The outer layers of the star are left behind in space as a planetary nebula. This leaves a dense core - a white dwarf.

23
Q

What happens when a white dwarf cool down?

A

When a white dwarf cools down, it will fade away, simply becoming a black dwarf.

24
Q

What do large mass stars become?

A

Large mass stars become red supergiants.

25
Q

What do low/medium mass stars become?

A

Low/medium mass stars become red giants.