1. Our Place in Space Where we are 1

2. We live on Earth 2 Welcome to Earf!

3. Earth orbits the Sun 3

4. The Earth is in the Solar System 4

5. The Solar System is the Milky Way 5

6. The Milky Way is a galaxy A galaxy is a  massive  gravitationally bound system that consists of  stars and stellar remnants  gas and dust  dark matter 6 We do not know what that is. Yet.

7. There are billions of galaxies 7

8. Scale of the Universe This stuff is FAR!

9. Sizes of things Earth diameter: 13,462 Km Mars diameter: 6,800 Km  About ½ Earth Jupiter diameter: 142,984  10+ times the Earth  1,000+ Earths would fit inside Sun diameter: 1.4 million kilometers  109 times Earth, almost 10 times Jupiter  1,000,000 Earths would fit inside

10. Distance Ladder

11. Distance to the Sun Earth is 149,597,871 Km from the Sun  92,955,807 miles This distance is 1 astronomical unit  AU

12. Astronomical Unit Mercury is.4 AU from the Sun Venus is 0.72 AU Mars is 1.52 AU Jupiter is 5.2 AU Saturn is 9.5 AU Uranus is 19.6 AU Neptune is 30 AU Kuiper Belt is 30 to 50 AU Oort Cloud is 50,000 to 100,000 AU!

13. Edge of the solar system Heliosphere - The bubble in the interstellar medium of space caused by the Sun’s wind

14. Beyond the solar system Beyond the solar system, the astronomical unit becomes too small  Like measuring distance around USA in millimeters Need a bigger unit of measure – the Light Year (LY) Light Year – distance light can travel in one year

15. Beyond the solar system Oort Cloud is about 2 LY in diameter Nearest star, Proxima Centauri, is 4.22 LY Center of Milky Way is 26,000 LY Milky way is 100,000 LY across Nearest Galaxy, Andromeda, is 2.5 million LY away Voyager 1 will take 18,000 years to go 1 LY

16. How do we know this? Measurement to distant objects is done with trigonometry Parallax - difference in the apparent position of an object viewed along two different lines of sight

17. Beyond the Light Year Parsec – uses parallax  Parallax of 1 arcsecond  3.26 LY  pc

18. Beyond the Light Year Parsec is for really big distances  Proxima Centauri = 1.29 parsecs  Galaxy RXJ1242-11 = 200 million pc  Edge of observable universe 14 billion pc

19. Distance Ladder

20. Spectroscopic Parallax Uses the color of a star to determine its absolute brightness Compared to apparent brightness to determine distance

21. Spectroscopic Parallax Imagine a distance candle The closer it is, the brighter it looks If you can measure how bright it looks, you can tell how far away it is

22. Distance Ladder

23. Cepheid in Virgo

24. Cepheid Variables Cepheids pulsate on a regular frequency  Days to months The slower they pulse, the brighter they are Determine how fast it pulses, determine its magnitude Determine the magnitude, determine the distance

25. Distance Ladder

26. Supernova! Sometimes a star dies in a massive explosion called a supernova Certain ones are called Type 1A All Type 1A supernovae are exactly the same brightness. Measure its brightness and determine the distance

27. Distance Ladder

28. This stuff is FAR!