# P7.4: The Sun, The Stars & Their Surroundings

HideShow resource information
• Created by: Lili
• Created on: 23-06-13 12:16
What Does the Colour of a Star Depend on?
Its temperature, the coolest stars appear red, slightly hotter ones look orange, then yellow, then white. The very hottest stars are blue-white.
1 of 28
What is a Spectrometer Used For?
To measure how much radiation is emitted at each frequency. To identify the peak frequency of a star.
2 of 28
What Does the Peak Frequency Do?
It gives an accurate value for the temperature of the sat. The greater the peak frequency, the higher the temperature. Luminosity also increases with temperature.
3 of 28
What is Spectra Used For?
Astronomers use spectra from stars to identify their elements.
4 of 28
How Do Electrons Move Between Energy Levels?
They will only move between energy levels if they are given exactly the right amount of energy.
5 of 28
What Happens When Light From a Star Passes Through its Atmosphere?
Some of the photons (packets of energy) have energy of exactly the right frequency to move electrons to higher energy levels. It is these frequencies that are missing from absorption spectra.
6 of 28
What is Ionisation?
This is if electrons are given enough energy they can leave the atom completely.
7 of 28
How Do Gases Behave?
The particles of a gas move very quickly in random directions. When they hit the sides of a container they exert a force as they change direction. This causes gas pressure.
8 of 28
What is the Correlation Between the Pressure and Volume of a Gas?
If you decrease the volume of the container, the particles hit the sides more often, the pressure increases.
9 of 28
What is the Correlation Between the Pressure and Temperature of a Gas?
The hotter the gas, the more energy its particles have, and the faster they move. This means particles hit the sides of the container harder and more often.
10 of 28
How Do You Convert the Kelvin Scale (K) into oC?
Temperature in K = Temperature in oC + 273 & Temperature in oC = Temperature in K - 273
11 of 28
What is the Equation For the Constant?
Pressure/Temperature = Constant & Volume/Temperature = Constant
12 of 28
How Does Decreasing the Temperature of a Gas at a Constant Pressure Affect its Volume?
Its volume decreases.
13 of 28
What is a Protostar?
Gravity compresses a cloud of hydrogen & helium gas; Gas particles get closer and closer; The volume of the gas cloud decreases; Gas particles fall towards each other, they move faster & faster; Temp & pressure increases; This mass of gas is the PS.
14 of 28
What is Nuclear Fusion?
This is when hydrogen nuclei come together closely enough, they may join to of nuclei of another nuclei of another element, helium. The process releases energy.
15 of 28
In a Nuclear Equation You Must Balance?
The Mass (Top Numbers), The Charge (Lower Numbers)
16 of 28
You Can Use Einstein's Equation to Calculate the Energy Released in Nuclear Fusion and Fission Reactions, What is the Equation?
E=mc2 Energy Released = Mass Lost x (Speed of Light in a Vacuum)2
17 of 28
Describe the Processes That Happen Inside a Main-Sequence Star.
Core - Temperature and Density are Highest. Most Nuclear Fusion Happens Here. Radioactive Zone - Energy is Transported Outwards from the Core by Radiation. Convection Zone - Convection Currents Flow Here, Carrying Heat Energy to the Photosphere...
18 of 28
Describe the Processes That Happen Inside a Main-Sequence Star....
Photosphere (surface of a star) - Energy is Radiated into Space from Here.
19 of 28
How is Energy Transported From the Core to the Surface by Radiation?
20 of 28
What is the Life Sequence for a Lighter Mass Star?
Birth of a Star, Main Sequence Lifetime, Red Giant, White Dwarf
21 of 28
What is the Life Sequence for a Heavy Weight Star?
Birth of a Star, Main Sequence Lifetime, Supergiant, Supernova, Neutron Star or Black Hole
22 of 28
How is a Red Giant/ Supergiant Formed?
The outer layers of the star, which contain hydrogen, then fall inwards. New fusion reactions begin in the core. These reactions make the outer layers of the star expand. The photosphere cools, and its colour changes from yellow to red.
23 of 28
How is a White Dwarf Formed?
The Sun has a relatively low mass. When it becomes a red giant it will not be compressed further once its helium has been used up. The star will shrink and become a white dwarf star. There is no fusion in a white dwarf, it generally cols and fades.
24 of 28
What is a Supernova?
This is when the core of a supergiant is mainly iron, it exposed. This is a supernova. It is so hot that fusion reactions produce atoms of elements as heavy as uranium.
25 of 28
What Happens After a Supernova?
A smaller core becomes a neutron star. A bigger core collapses to become a black hole. A black hole has so much mass concentrated into a tiny space that even light cannot escape from it.
26 of 28
What is the Hertzsprung-Russel (H-R) Diagram?
The H-R diagram is a plot of the luminosity of a star against its temperature. Different types of stars are in different regions of the graph.
27 of 28
What Are Exoplanets?
Astronomers have found convincing evidence of planets orbiting nearby stars. These are exoplanets.
28 of 28

## Other cards in this set

### Card 2

#### Front

What is a Spectrometer Used For?

#### Back

To measure how much radiation is emitted at each frequency. To identify the peak frequency of a star.

### Card 3

#### Front

What Does the Peak Frequency Do?

### Card 4

#### Front

What is Spectra Used For?

### Card 5

#### Front

How Do Electrons Move Between Energy Levels?