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Stars. Nebula – massive cloud of dust and gas in the universe. Nebulas are; Star nurseries Star graveyards. Measurement of distance in space. Light – year – distance that travels in one year 287,000m/sec – speed of light 1 ltyr = 6 trillion miles

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Presentation Transcript

Nebulas are;

    • Star nurseries
    • Star graveyards
measurement of distance in space
Measurement of distance in space
  • Light – year – distance that travels in one year
    • 287,000m/sec – speed of light
    • 1 ltyr = 6 trillion miles
    • Proxima Centauri – nearest star other than sun
      • 4.3 light years
measurement of distance in space1
Measurement of distance in space
  • Parallax – the apparent shift in the position of an object when viewed from two different positions
  • Determined by observing a star at two different points in its orbit around sun.
  • Star’s position appears to change in relationship to the background star.
what are stars
What are stars ?
  • Stars – massive balls of gases
    • Held together by gravity
    • rotating
      • Color of stars –
        • Temperature
        • Red – coolest
        • Blue - White – hottest
      • Composition of stars
        • Spectrum –
          • Spectroscope acts as a prism

A spectroscope helps us find out what stars are made of. It disperses, or separates, white light from a star into a very wide spectrum of colors — much wider than a normal prism does. When spread very wide, black lines appear in the spectrum.


Spectrum – from star tells astronomer:

      • Temperature
      • Composition
      • Show absorbed elements(black lines)
      • Each element has unique pattern of black lines
      • Like a fingerprint each pattern denotes elements that compose the star.

Absolute magnitude –

amt. of light produced by a star

Apparent magnitude –

measure of amt of light received by the earth

affected by:

1. size of star

2. temperature of star

3. distance of star

  • A first magnitude star is very bright,
  • a sixth magnitude star is at the limit of normal vision.
hr diagram relationship between temperature color and size
HR Diagram – relationship between temperature, color and size
  • Based on this evidence, we conclude
    • Stars spend most of their lives as main sequence stars.
    • During its lifetime, the surface temperature and luminosity stays pretty much constant.
    • The star's mass determines what the temperature and luminosity is during the star's main sequence lifetime.
      • More mass -> hotter.
      • More mass -> more luminous.
      • Also, more mass -> bigger.

Which named star on the H-R Chart has the greatest absolute magnitude?

    • Rigel
  • What is this star’s temperature?
    • 15,000 K
  • Red giants have the same color and temperature as red dwarfs. How do these star types differ from one another?
    • Red giants more massive than red dwarfs
  • What is the range of absolute magnitude for yellow giants on the diagram?
    • -1 to -4

Antares is a red giant. Is this star hot or cool? Explain.

cool; red shows cooler temps from an expected surface area.

What is the absolute magnitude of the sun?


What conditions do the H-R chart show between stars?

absoulte magnitude, temperature, size

where on the h r chart do the following stars fall
Where on the H-R chart do the following stars fall?
  • Star Absolute mag Temp
  • A +10 10,000 K
  • B -2 3,500 K
  • C +3 7, 000 K
  • D -9 6,000 K
  • Which star is a giant?


Which star is a dwarf


Which star is a supergiant?


Which star is like the sun?


main sequence stars
Main sequence stars
  • Everyday ordinary stars
  • Our sun – Sol
  • Energy – fuses H into He
red giants
Red giants
  • H is depleted
  • Core contracts and temps rise
  • Outer atmosphere expands and cools
  • Core begins to change He into C
white dwarf
White dwarf
  • Uses up H and He
  • Core implodes on self
  • Gets very hot and explodes gaseous atmosphere
  • Core very denseand very hot
neutron star
Neutron star
  • So dense 1tsp weighs 600 million metric tons
  • Some become pulsars
black hole
Black hole

A Black Hole is a region of space where the gravitational force is so strong that not even light can escape from it.

sol our sun
Sol our sun
  • Photosphere – surface of sun
    • Light given off
    • Temps. 6.000K
    • Granulation – due to rising of energy onto surface

Corona – largest layer of sun’s atmosphere

- temps 2million K

- gives off solar wind


Core – interior of sun where fusion takes place

  • Radiation zone – interior where radiation moves through
  • Convection zone – energy moves to photosphere in a swirling motion making granules.
surface features of sun
Surface features of sun
  • Sunspots – cooler darker areas on sun
      • Rotate around sun
      • Equator 25days
      • Pole 35 days
      • Occur in pairs of opposite charges
      • Caused by magnetic forces from sun’s rotation

Sunspot cycles – come in cycles of 11 years.

    • High part of cycle – produces greater solar wind
    • Interfere with communication satellites and radio transmissions
    • Cause auroras
  • Huge arching columns of gas which shoot out and are drawn back to the sun’s surface.
solar wind
Solar wind
  • The solar wind streams off of the Sun in all directions at speeds of about 1 million miles per hour.
  • Two to three days to travel.
  • The source of the solar wind is the Sun's hot corona.
  • The temperature of the corona is so high that the Sun's gravity cannot hold on to it.
  • Ions from sun
  • Interferes with communication satellites.