Review

1. Review Greeks knew all planets – Uranus Galileo observed that Venus goes through phases Look at sun .. We see photosphere Heliocentric – planets go around sun Liquid water on Mars Neptune discovered by gravitational effect on Uranus. Kepler discovered planets orbit in an ellipse. Asteroid belt between Mars and Jupiter Europa good for life – water under crust Solar Eclipse – we see corona and chromosphere Venus – like us in size and density Jupiter and Uranus both blue/size Uranus – rotates on its side

2. Telescopes • Galileo invented. • Reflecting • (bounce light) • Refracting • (bend light)

3. Telescopes of the Past

4. EM Spectrum – includes all the different types of EM waves!

5. Radio Telescopes - - focus radio waves on small antennas

6. Observatories – building w/1 or more telescopes • Located on mountains to be above part of the atmosphere!Mauna Kea – 4200 m above sea level.

7. Light through a prism = spectrum

8. Telescopes in Space • X rays, gamma rays, and most UV radiation blocked by our atmosphere. Hubble telescope is in space – has 2.4 meter mirror – gives visible light, uv, and infrared radiation.

9. Pictures taken by the Hubble • The Cat’s Eye Nebula

10. The Sombrero Galaxy 28 million light years away

11. The Trifid Nebula 9000 light years away!

12. Constellations – groups of stars. This one is Cassiopeia • We use these to locate objects in night sky

13. How do we classify stars?(size, brightness, temperature) Star that is 3200 degrees Celcius – red, 6000 degrees – yellow, 20000 degrees - blue

14. Made of? 73% hydrogen (H) 25% Helium (He) 2% % other.

15. Brightness of stars depends on size and temp. • Apparent Brightness (brightness as seen from Earth. • Absolute brightness – brightness it would have if it were at a standard distance from Earth. This depends on its size and temp! • Astronomers must find apparent brightness and its distance from Earth!

16. How far are stars? Light year – the distance that light travels in one year (185,000 miles/second) Parallax – used to determine a star’s distance from Earth.

17. HR Diagram. .

18. More than 90% of stars are in Main sequence.

19. Main sequence stars increase in brightness as they increase in temp

20. Stars begin with nebula – gas and dust • Large? Gravity – is force that pulls matter in stars together. When HOT enough on the surface, nuclear fusion begins - protostar • Life of star depends on mass ..small stars live longest (200 billion years), huge stars die young(10 million). • Our sun is 4.6 billion years old now. ½ way

21. Death begins when fuel runs out • Core shrinks, outer part expands, it becomes either a • White dwarf, • (low mass star) • Neutron star • Black hole

22. Draw this

23. High mass star • Supernova – supergiant runs out of fuel – explodes suddenly. Some of material expands into space. May become part of another nebula. • Neutron star -Smaller, denser than white dwarfs. Some spin and give off pulsating radio waves – Pulsars • Black holes – from most massive stars - gravity so strong that nothing can get out . X rays hot gases being pulled in

24. Most stars are members of groups ..of 2 or more stars ..called star systems • 2 stars – binary – wobble due to gravity • Eclipsing binaries – they become dimmer at regular intervals • Planets - pull toward and away. .many planets near stars . Most are large like Jupiter. • Star Clusters – Open – loose, • disorganized, a few thousand. • Globular – large, older stars, • Round, millions!

25. Galaxies • Spiral – Our Milky Way • Pinwheel shape, few new stars in center, • Arms have new stars and lots of gas/dust

26. Elliptical • Flattened disc – billions of stars, little gas, old

27. Irregular • Small, many young, bright stars . .lots of gas and dust

28. Quasars • Young galaxies. Gas heats up as it gets pulled toward giant black holes...shining brightly