Stellar Evolution Flashcards
The Sun
Our nearest star is the Sun. it’s approximately 150 million kilometres from the Earth.
Understand how stars can be classified according to their colour
Different stars have different colours. The colours of the stars tells us about their temperatures. Using the colours of stars and their surface temperatures, scientists had created different groups of stars. These groups are called O,B,A,F,G,K,M.
O and B are the hottest stars.
K and M are the coolest stars.
Star classification and their colour and surface temperature
O - blue - more than 33 000
B - blue white - 33000-10000
A - white - 10000-7500
F - yellow white - 7500-6000
G - yellow - 6000-5200
K - Orange - 5200-3700
M - red - 3700-2000
You can use the mnemonic ‘ Oh Be A Fine Guy and Kiss Me’
The brightness of a star
The brightness of a star depends on:
- The distance of a star is from Earth
- What the star is made of
- Types of nuclear fusion happening
Because of these factors, there are a couple different ways for people to describe the brightness of a star:
The apparent brightness - how bright it seems from an observer on Earth. This depends on:
- Luminosity of the star - a measure of how much energy per second is radiated out in the form of light.
- Distance of the area from Earth
The absolute brightness - now bright stars appear if they were all placed the same distance away from Earth. This depends only on the luminosity of the star.
Describe the evolution of stars of similar mass to the Sun
All stars are born from a cloud of dust. This dust is made from hydrogen and helium. This cloud of dust is known as a nebula. The hydrogen and helium get closer together due to gravity until eventually it is so hot and dense, it starts to fuse, this means that the star is born. Very young stars are protostars. As these stars fuse more fuel, they grow into main sequence stars. Our Sun is currently a main sequence star. Eventually, the hydrogen and helium run out. When this happens, the star starts to expand and cool down until it turns into a red giant star. Eventually, the outer layers of the red giant will escape from the main body and go into space becoming a plantery nebula. The rest of the star that is left behind is very hot and dense. This is a white dwarf star. This will eventually cool down and turn into a black dwarf star.
Draw the main components of the Hertzsprung Russell diagram (HR diagram)
Two scientists discovered the relationship between the brightness of a star and its surface temperature. They created a diagram that shows the relationship between the brightness, temperature and classification of a star. The letters at the bottom is the star classifications and the numbers is the luminosity of a star
Look in pics for the HR diagram
