Beyond Our Solar System

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Beyond OurSolar System

• Ch. 25

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• star a body of gases that gives off a
  tremendous amount of radiant energy in the form
  of light and heat

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Star Groups

• constellations a group of stars that form a
  pattern in the sky (88 different ones)

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Orion
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Ursa Minor
Ursa Major
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Composition and Temperature

• stars differ in size, density, mass, and
  composition

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• color of a star depends on its surface
  temperature
• hot stars are blue (average surface temperature?
  35,000 K)
• cool stars are red (average surface temperature?
  3,000 K)
• our sun is yellow (average surface temperature?
  5,500 K)

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Parallax
the slight shifting of the apparent position of
a star due to the orbital motion of Earth.
the nearest stars have the largest parallax
angles, while those of distant stars are too
small to measure.
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Distance to Stars

• light-year the distance light can travel in one
  year (9.5 trillion km)
• it takes 8 minutes for the suns light to reach
  Earth
• closest other star- Alpha Centauri (4.3 l.y.a)

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Motion

• actual motion must be measured only with a
  telescope
• apparent motion motion due to the Earths
  movement

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Stellar Magnitudes

• apparent magnitude how bright a star appears
  from Earth- the lower the number, the brighter
  the object
• absolute magnitude how bright a star really is

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Distance, Apparent Magnitude, and Absolute
Magnitude of Some Stars
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Life Cycle of a Star
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• nebula a cloud of gas and dust

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• protostar shrinking, spinning, glowing nebula
  (temperature rises)

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Nuclear fusion begins- a star forms!
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• main sequence star longest stage of life cycle-
  nuclear fusion releases energy

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• red giant very large, cool bright stars- starts
  when hydrogen is used up- star cools and outer
  layers expand- size is 10xs bigger than our sun-
  this is next stage of our sun!

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• white dwarf small, hot, dim star- outer gases
  are lost and only core remains

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• supergiant extremely large, cool giant stars-
  very bright- 100 xs larger than the sun

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• supernova star that blows apart with a
  tremendous explosion- occurs in very massive stars

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• neutron star collapsed core of a supernova-
  dense ball of neutrons

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• black hole hole in space with gravity so great
  that not even light escapes- formed from
  collapsed supernova

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Classification of Stars

• H-R Diagram graph plotting surface temperature
  and absolute magnitude of each star

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• galaxies large scale groups of stars held
  together by gravity
• there are 50 billion-1 trillion galaxies
• we are in the Milky Way galaxy

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Images of the Milky Way Galaxy
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Types of Galaxies

• spiral bright center of stars with arms
  spiraling out
• Milky Way is a spiral

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Andromeda Galaxy
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Structure of the Milky Way
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• barred spiral have a group of stars making a bar
  through the center

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• elliptical shape ranges from spherical to oblong
• no arms

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• irregular small, faint stars spread out
  unevenly with no pattern

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Large Magellanic Cloud
Small Magellanic Cloud
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Galaxy Cluster
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The Big Bang
? The big bang theory states that at one time,
the entire universe was confined to a dense, hot,
supermassive ball. Then, about 13.7 billion years
ago, a violent explosion occurred, hurling this
material in all directions.
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