Scientists often do “scaling” do avoid all those large numbers. Scientists often do “scaling” do avoid all those large numbers


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Scientists often do “scaling” do avoid all those large numbers.

  • Scientists often do “scaling” do avoid all those large numbers.

  • For example, the Sun is ABOUT a million times the mass of the Earth and a hundred times the size.



What is the surface gravity of the Moon in gees? R=.01Re, M=.25Me?

  • What is the surface gravity of the Moon in gees? R=.01Re, M=.25Me?

  • a).04

  • b)4

  • c)16

  • d).16













Fahrenheit –

  • Fahrenheit –

    • 0=salt water freeze 100=human body
  • Celsius

    • 0=pure water freeze 100=water boil (sea level)
    • C=(F-32)x5/9
  • Kelvin

















H hydrogen 89% by number

  • H hydrogen 89% by number

  • He helium 11%

  • O oxygen 0.1%

  • C carbon 0.06%

  • N nitrogen 0.015%













































Formed from cloud 4.6x109 years ago

  • Formed from cloud 4.6x109 years ago

  • Collapsed to present size

    • stabilized by nuclear reactions
  • Emits 4x1026 W

  • Runs on proton-proton chain and CNO cycle

  • Now 20% brighter

  • Turbulent upper envelope

  • Magnetic Fields from Differential Rotation

  • Sunspots, Corona, Solar Wind

  • Activity Cycle 11 years





Sun and all the stars we see are part of Milky Way Galaxy



Closest Star, Proxima Centauri is 4x1016m away. (Alpha Cen ~4.3x1016m)

  • Closest Star, Proxima Centauri is 4x1016m away. (Alpha Cen ~4.3x1016m)

  • Need a more convenient unit





There’s a big black hole in the Center of the Milky Way at a distance of 3x1020m. How long does it take for its light to reach us?

  • There’s a big black hole in the Center of the Milky Way at a distance of 3x1020m. How long does it take for its light to reach us?

  • A) 3years

  • B) 30 years

  • C) 300 years

  • D) 3000 years

  • E) 30,000 years



There’s a big black hole in the Center of the Milky Way at a distance of 3x1020m. How long does it take for its light to reach us?

  • There’s a big black hole in the Center of the Milky Way at a distance of 3x1020m. How long does it take for its light to reach us?

  • A) 3years

  • B) 30 years

  • C) 300 years

  • D) 3000 years

  • E) 30,000 years









Arabic Names

  • Arabic Names

    • Antares, Capella, Mira, etc.
  • Constellations

    •  Orionis,  Cygni, … then 49 Ori, 50 Ori, etc.
  • Catalogues HD80591, SAO 733421, etc

  • RA and Dec – just position in the sky









Based on the definition of a parsec , if star A has a parallax of 0.5 arcseconds and star B has a parallax of 0.75 arcseconds which one is farther from the Earth?

  • Based on the definition of a parsec , if star A has a parallax of 0.5 arcseconds and star B has a parallax of 0.75 arcseconds which one is farther from the Earth?

  • A. Star B is farther away because it has a higher parallax

  • B. Star A is farther away because it has a lower parallax

  • C. All stars are the same distance away from the Earth

  • D. It is impossible to tell from this information.



Based on the definition of a parsec , if star A has a parallax of 0.5 arcseconds and star B has a parallax of 0.75 arcseconds which one is farther from the Earth?

  • Based on the definition of a parsec , if star A has a parallax of 0.5 arcseconds and star B has a parallax of 0.75 arcseconds which one is farther from the Earth?

  • A. Star B is farther away because it has a higher parallax

  • B. Star A is farther away because it has a lower parallax

  • C. All stars are the same distance away from the Earth

  • D. It is impossible to tell from this information.





The parallax of an observed star is 0.1 arcseconds, how many lightyears is it away from Earth?

  • The parallax of an observed star is 0.1 arcseconds, how many lightyears is it away from Earth?

  • a. 1 light year

  • b. 3 light years

  • c. 10 light years

  • d. 30 light years

  • e. 75 light years



The parallax of an observed star is 0.1 arcseconds, how many light years is it away from Earth?

  • The parallax of an observed star is 0.1 arcseconds, how many light years is it away from Earth?

  • a. 1 light year

  • b. 3 light years

  • c. 10 light years

  • d. 30 light years (10parsecs)

  • e. 75 light years




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