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Stars - PowerPoint PPT Presentation

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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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Nebula massive cloud of dust and gas in the universe
Nebula – massive cloud of dust and gas in the universe

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

  • 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.

  • Luminosity – how much radiation a star is emitting.

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 magnitude? 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? magnitude?

  • 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 magnitude?

  • Everyday ordinary stars

  • Our sun – Sol

  • Energy – fuses H into He

Red giants
Red giants magnitude?

  • H is depleted

  • Core contracts and temps rise

  • Outer atmosphere expands and cools

  • Core begins to change He into C

White dwarf
White dwarf magnitude?

  • 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 magnitude?

  • So dense 1tsp weighs 600 million metric tons

  • Some become pulsars

Black hole
Black hole magnitude?

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

Sol magnitude?

Sun s layers
Sun’s layers magnitude?

Sol our sun
Sol our sun magnitude?

  • Photosphere – surface of sun

    • Light given off

    • Temps. 6.000K

    • Granulation – due to rising of energy onto surface

  • Corona magnitude? – largest layer of sun’s atmosphere

    - temps 2million K

    - gives off solar wind

  • Core magnitude? – 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 magnitude?

  • 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 magnitude?– come in cycles of 11 years.

    • High part of cycle – produces greater solar wind

    • Interfere with communication satellites and radio transmissions

    • Cause auroras

Prominence magnitude?

  • Huge arching columns of gas which shoot out and are drawn back to the sun’s surface.

Solar wind
Solar wind magnitude?

  • 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.