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NUMBERS IN ASTRONOMY

NUMBERS IN ASTRONOMY See Appendix 4 & 5 Some numbers are very small E.g. Diameter of Hydrogen Atom is about 0.00000001 cm .0000000000001 cm Proton Electron .00000001 cm Hydrogen Atom NUMBERS in ASTRONOMY NUMBERS in ASTRONOMY Some numbers are very small Other numbers are very large

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NUMBERS IN ASTRONOMY

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  1. NUMBERS IN ASTRONOMY See Appendix 4 & 5

  2. Some numbers are very small • E.g. Diameter of Hydrogen Atom is about 0.00000001 cm .0000000000001 cm Proton Electron .00000001 cm Hydrogen Atom NUMBERS in ASTRONOMY

  3. NUMBERS in ASTRONOMY • Some numbers are very small • Other numbers are very large • E.g. size of galaxy 100,000,000,000,000,000,000,000 cm • E.g. Diameter of Hydrogen Atom is 0.00000001 cm

  4. 100,000,000,000,000,000,000,000 cm

  5. NUMBERS in ASTRONOMY • Some numbers are very small • The number of zeros is denoted by an exponent of 10. • This exponent is positive if the number is larger than 1. • 10N is 1 followed by N zeros • E.g. 100,000,000,000,000,000,000,000 is written as 1023 • The exponent (power) is negative if the number is smaller than 1. • 10-N represents a 1 in the Nth place after the decimal • E.g. 0.00000001 is written as 10-8 • E.g. size of Hydrogen Atom (GS) is 0.00000001 cm • Other numbers are very large • E.g. size of galaxy 100,000,000,000,000,000,000,000 cm • Powers of 10 Notation

  6. POWERS OF 10 NOTATION • 10N is 1 followed by N zeros • 103 is 1000 • 108 is 100,000,000 • 10-N is a 1 in the Nth decimal place after the decimal point • 10-3 is 0.001 • 10-8 is 0.00000001 • More complicated numbers are represented by a combination of a power of 10 and a multiplying factor • 0.000000025 is 2.5 x 10-8 • 64,000 is 6.4 x 104

  7. NUMBERS IN ASTRONOMY • Rule for Multiplication • Multiply the factors and add the powers • E.g. 2 x 104 times 3 x 105 is   (2x3) x 10(4+5) = 6 x 109 • Rule for Division • Divide the factors and subtract the powers • E.g. 5 x 106 divided by 2 x 104 is (52) x 10(6-4) = 2.5 x 102

  8. Answer: 1.989 x 1030 kg TEST YOURSELF • The mass of the Sun is: 1,989,000,000,000,000,000,000,000,000,000 kg. Write this mass in the powers-of-ten notation.

  9. The Gross National Product of Canada in 2000 was 7.6 x 1011 Canadian Dollars. There are 3 x 107 people in Canada. What is the amount of GNP per person? A) 2.5 x 103 B) 2.5 x 104 C) 2.5 x 105 D) 2.5 x 106 FLASHCARD

  10. FLASHCARD The centre of our Galaxy is 7 x 1016 km from us. UNBC (in Prince George) is about 5 x 102 km away from us. How many times farther (in powers of 10 notation) is the Galactic centre from us compared to UNBC? A) 3.5 x 1019 B) 1.4 x 108 • C)1.4 x 1014 • D) 7.1 x 10-15

  11. The mass of our Galaxy is about 7 x 1011 times the mass of our Sun. There are about 1011 galaxies in the Universe. If an average star weighs about half that of our Sun, about how many stars are there in the Universe? A) 7 x 10121 B) 14 x 1022 C) 7 x 1022 D) 7 FLASHCARD

  12. POWERS of TEN EXAMPLESSizes in Meters

  13. UNITS in ASTRONOMY • Mass: kilograms (kg) • Time: seconds (s) or years (y) • Distance: meters (m), kilometers (km), light years (ly), or Astronomical Units (AU) • A light year is the distance light travels in one year • Speed of light = 3 x 105 km/s • There are 3 x 107 seconds in a year • Thus a lightyear is (3 x 105) x (3 x 107) = 9 x 1012 km • An Astronomical Unit is the mean distance between Earth and the Sun (1.5 x 108 km)

  14. UNITS in ASTRONOMY • Light year: • This is the distance which light will travel in the period of 1 year • The speed of light (c) is 3 x 105 km/s • There are 3 x 107 seconds in a year • Thus, a light year is (3 x 105) x (3 x 107) = 9 x 1012 km • Note: the star nearest the Sun (Proxima Centauri) lies at a distance of 4.26 ly (or 38 million million km!) • Astronomical Unit: • This is the mean Earth-Sun distance, and is about 1.5 x 108 km ( 150 million km) • Solar Mass • This is a convenient unit to use for mass and is equal to the mass of our own Sun (1.9891 x 1030 kg) • Your instructor weighs in at a hefty 4 x 10-29 solar masses

  15. UNITS in ASTRONOMY • Temperature: • Use Degrees Kelvin (K) • K = C + 273 • C water freezes at 0C boils at 100C • K water freezes at 273K boils at 373K • Room Temperature about 300K • 0K = - 273C is absolute 0

  16. 360 degrees 270 degrees 90 degrees 180 degrees ANGULAR MEASUREMENT 0°

  17. 1 degree = 60 minutes 1 minute = 60 seconds ANGULAR MEASUREMENT 360 degrees in a full circle

  18. ANGULAR MEASUREMENT

  19. WHAT IS THE ANGULAR SIZE OF THE MOON AS SEEN FROM THE EARTH? A)0.5 degree B) 5 degrees C) 10 degrees D) 50 degrees FLASHCARD

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