Stars

1. Constellations – Patterns that appear in the sky they appear as mythological characters, animals or common objects Polaris is the North Star and was used by ancient mariners in navigation. Stars

2. When we refer to the brightness of a star we are referring to it’s absolute or apparent magnitude. Absolute Magnitude is a measure of how much light a star gives off. Apparent Magnitude is a measure of the amount light that Earth receives. Absolute and Apparent Magnitude

3. Parallax – A way to measure the distance of stars by observing the shift in position when viewing the star from 2 different positions. Light Year – The distance that light travels in 1 year. It is 300,000 km per second or about 9.5 trillion km per year. This distance is used by astronomers who want to measure distance in space between stars, galaxies and other objects. Measurements in Space

4. Color – The color of a star indicates it’s Temperature. Hot stars appear as white/blue Cool stars appear as orange/red Our sun and stars like it are yellow They fall between Hot and Cool stars Properties of stars

5. Our sun is defined as an average star. It shines with yellow light. Our sun does not have any companion stars 2 stars that orbit each other are known as binaries. Stars can also be clustered close together. This is when several stars are gravitationally attracted to each other The Sun

6. We use a star classifying chart called the Hertzsprung- Russell diagram. This diagram uses temperature and brightness to classify stars Stars in the upper left of the diagram are the Hottest stars while stars at the lower right are the coolest stars Classifying stars

7. Most stars appear in the Hertzsprung-Russell diagram as Main sequence stars. Most main sequence stars are found as cool stars in the lower right hand corner of the diagram. Main sequence

8. 10% of the stars do not fall in the main sequence of the H-R diagram Some stars are small and hot but not bright. These appear in the lower left of the Diagram and are known as White Dwarfs Some stars are extremely bright but not very hot. These are known as Red Giants or Supergiants. They are found in the upper Right hand of the H-R Diagram Dwarfs and Giants

9. All stars use nuclear fusion as their main source of energy. This is a process where 2 atoms are fused or forced together creating a new atom of a different element. Fusion

10. Stars begin as large clouds of dust and gas called Nebula Gravity causes these particles to attract each other and contract. When the temperature inside these nebula reach 10 million degrees fusion begins and a star is born Evolution of Stars

11. When a star is born the temperature of a star causes pressure to increase. The gravity and pressure reach a balancing point and the star remains on the main sequence of the H-R diagram Main Sequence stars

12. When all of the stars hydrogen is used up the star’s core contracts heating up the core and the star begins to fuse heavier elements. As this occurs the star’s outer layers expand and cool. The star has become a Giant and moves off the main sequence into the Giant part of the H-R diagram. Giants

13. As the core of a star gets hotter it’s outer layers escape into space leaving behind a core the size of the Earth. This core is a Hot dense star known as a white dwarf. Our sun will eventually become a white dwarf White dwarfs

14. Stars that are 8 times the size of our sun do not become white dwarfs. These stars become supergiants and when they die they go through a process called supernova. Supergiants

15. This occurs when a stars core Is made up of Iron and can no longer fuse atoms for energy. The core Collapses and the outer layers of the star explodes creating a brightness millions of times brighter then our sun. The remnants of the star will become a Neutron star or a Black Hole Supernova

16. All of the elements found in our solar system were produced through the evolutionary process of stars. The matter in stars is recycled over and over again creating new stars and new solar systems throughout the universe Elements

17. A galaxy is a large group of stars , gas and dust held together by gravity 3 Types of galaxies Spirals – These galaxies have a large center and arms that extend outward in the form of a spiral. The milky way is a spiral galaxy Elliptical – These are galaxies that are shaped like footballs or are round Galaxies

18. Irregular – These galaxies have many different shapes and do not fit into the elliptical or Spiral galaxies Galaxies

19. The Big bang theory – To explain why the universe is continually expanding scientists believe a large explosion occurred 13.7 billion years ago. After this explosion the entire universe began to expand everywhere at the same time and continues to do so. The origins of the Universe