Survey of the Universe Tom Burbine tburbine@amherst

1. Survey of the UniverseTom Burbinetburbine@amherst.edu

2. Readings • Should start reading Units 1-4

3. Stellarium • Everybody should download the program Stellarium • http://www.stellarium.org/ • Need to change your location

4. Office Hours • M-W 10-11 am in Kendade 221

5. Help Sessions • 7-10 pm on Sundays and Tuesdays • First Help Session will be Feb. 3 in Kendade (email on room number later)

6. HW #1 • HW #1 is due Feb. 6

7. Stars • Stars are composed primarily of Hydrogen and Helium • Generate energy through nuclear fusion

8. Sun • Our star • Typical star since the msses of stars range from 0.1 to 100 solar masses • 1 solar mass is the mass of the Sun http://www.aerospaceguide.net/solar_system/sun.html

9. Stellar evolution • Stars are born • Live • And then die

10. Galaxies • Galaxies are massive gravitationally bound systems of stars and stellar remnants, gas, dust, planets, and dark matter • Dark matter is matter that you can’t see but whose gravity affects visible matter and background radiation

11. Milky Way Galaxy • Our Galaxy • 100-400 billion stars http://www.astro.keele.ac.uk/workx/milkyway/page.html

12. Galaxies • Taken over 11 days • Over 10,000 objects apparent (majority are galaxies)

13. There are estimated to be more than 176 billion galaxies in the observable universe

14. Light-year • Distance that light travels in a year • Light travels at a speed of 300,000,000 m/s in a vacuum • 1 light year = 10,000,000,000,000,000 meters

15. Local Group • Gravitationally bound group of galaxies that the Milky Way is a member of • Contains more than 30 galaxies http://hendrix2.uoregon.edu/~imamura/123/lecture-3/lecture-3.html

16. Big Bang • Explosion that started the Universe

17. Why do we use the metric system in science?

18. A system based on multiples of 10 is much more intuitive for humans • We are born with 10 fingers and toes • The math system that we use is based on 10

19. Metric System • Any system of measurement needs three fundamental units • Length - meter • Mass - kilogram • Time - second

20. 1 kilometer = 1,000 meters • 1 meter = 100 centimeters • 1 centimeter = 10 millimeters • 1 kilogram = 1,000 grams

21. Things you need to know because we will use the metric system • one kilometer is 5/8 of a mile • one meter is 3.28 feet • one centimeter is 0.39 inches • 1 kg (mass) is equivalent to 2.2 pounds (force) on Earth • We will use the metric system in this class • Does anybody remember the Mars Climate Orbiter?

22. Mars Climate Orbiter • Software calculated forces for the thrusters in English units (pounds). • People controlling the spacecraft thought the calculated forces were in Newtons (metric). (One English pound of force equals 4.45 Newtons.) • Changes made to the spacecraft's trajectory were actually 4.45 times greater than what the JPL navigation team believed. • The spacecraft missed its intended 140 - 150 km altitude above Mars during orbit insertion, instead entering the Martian atmosphere at about 57 km. • The spacecraft was destroyed http://en.wikipedia.org/wiki/Image:Mars_Climate_Orbiter_2.jpg

23. 1 kilometer = 1,000 meters • 1 meter = 100 centimeters • 1 centimeter = 10 millimeters • 1 kilogram = 1,000 grams • one kilometer is 5/8 of a mile • one meter is 3.28 feet • 1 kg (mass) is equivalent to 2.2 pounds (force) on Earth

24. Meter • How is the meter defined?

25. Meter • Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole • International Prototype Meter was defined as the distance between two lines on a standard bar composed of an alloy of ninety percent platinum and ten percent iridium, measured at the melting point of ice.

26. Meter • Now defined as equal to the distance travelled by light in vacuum during a time interval of 1⁄299,792,458 of a second.

27. Gram and Kilogram • How are the gram and kilogram defined?

28. Gram and Kilogram • How are the gram and kilogram defined?

29. Gram and Kilogram • A gram was first decreed to be equal to “the absolute weight of a volume of water equal to the cube of the hundredth part of the meter, at the temperature of melting ice.” • Now, the International Prototype Kilogram is used as the standard. • It is made of a platinum alloy known as “Pt‑10Ir”, which is 90% platinum and 10% iridium

30. International Prototype Kilogram • Photo of Danish national kilogram prototype

31. Other Units used in Astronomy • Solar mass – Mass of Sun • Jupiter mass – Mass of Jupiter • Light year – Distance light travels in a year • Astronomical Unit – Average distance between the Sun and the Earth • Speed of light (c) - 3 x 108 m/s

32. Scientific Notation • 10000 = 104 • 100000000 = 108 • 10000000000 = 1010 • 100000000000000000000 = 1020 • 0.001 = 10-3 • 0.0000001 = 10-7

33. How do you write numbers? • 31,700,000 = 3.17 x 107 • 2,770,000 = 2.77 x 106 • 0.00056 = 5.6 x 10-4 • 0.0000078 = 7.8 x 10-6

34. How do you do multiply? • 106 x 108 = 10(6+8) = 1014 • 10-5 x 103 = 10(-5+3) = 10-2 • (3 x 104 ) x (4 x 105) = 12 x 10(4+5) = 12 x 109 = 1.2 x 1010

35. How do you divide? • 108/106 = 10(8-6) = 102 • 10-6/10-4 = 10(-6-(-4)) = 10-2 • (3 x 108)/(4 x 103) = ¾ x 10(8-3) = 0.75 x 105 = 7.5 x 104

36. Always use units for your answers

37. Stars in the Universe • Say there are 100 billion galaxies • Each galaxy has 100 billion stars • So how many stars in the universe

38. Answer • Number of stars in universe • = (100 x 109) x (100 x 109) = 10000 x 1018 = 1 x 1022 = 10,000,000,000,000,000,000,000 • This is about the same number of grains of sand in every beach in the world

39. Questions: • How many of these 1022 stars have planets? • How many of these planets have life?

40. Any Questions?