The Sun – Our Star The closest star to Earth Medium size Yellow Main Sequence Star 150,000,000 Km (93 Million miles) away billion years old Will last about another 5 billion years Located near the edge of our disc shaped galaxy – The Milky Way

Stars Huge bright balls of gas

What are Stars Gigantic spheres of gases held together by gravity Generate huge amounts of energy because of nuclear reactions of hydrogen and other elements. Radiate electromagnetic radiation. –Light, heat and other forms of energy There are 100 billion stars in our own galaxy!

Nebulas – Stellar Nurseries Giant clouds of gas and dust in space Where new stars are formed

Stars The Sun is the closest star to Earth – 150,000,000 km away The next closest star is Proxima Centauri – 39,900,000,000,000 km away –4.2 light years Stars are extremely far away!!! The Sun is thousands of times closer to Earth than other stars The Sun Proxima Centauri

Stages of a Stars Life Cycle

Classifying Stars ClassColorSurface Temp. (degrees Celsius) Elements detected Examples of stars O BlueAbove 30,000Helium10 Lacertae B Blue-white10, ,000Helium and Hydrogen Rigel, Spica A Blue-white7, ,000HydrogenVega, Sirius F Yellow- white 6, ,500Hydrogen and heavier elements Canopus, Procyon G Yellow5, ,000Calcium and other metals The sun, Capella K Orange3, ,000Calcium and Molecules Arcturus, Aldebaran M RedLess than 5,000MoleculesBetelgeuse, Antares

H-R Diagram Analyze the graph!

Hertzprung–Russel (H-R) Diagram - a graph that shows the relationship between a star’s surface temperature and it’s absolute magnitude.