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

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

• 0=absolute zero 100 degrees between freeze and boil
• K=C+273
• -273C = 0K = Absolute Zero

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

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

• We all orbit a common center

• Sun is 3x1020m from center of MW

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