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Stars. Distances To The Stars. Stars are separated by vast distances. Astronomers use units called light years to measure the distance of stars A light-year is the distance that light travels in a vacuum in a year Proxima Centauri, is the closest star to the sun.

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Distances to the stars l.jpg
Distances To The Stars

  • Stars are separated by vast distances.

  • Astronomers use units called light years to measure the distance of stars

  • A light-year is the distance that light travels in a vacuum in a year

  • Proxima Centauri, is the closest star to the sun.

Measuring_Distance_in_Space__The_Light_Year


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Parallax

  • Astronomers have developed various methods of determining the distance of stars.

  • The change in position of an object with respect to a distant background is called parallax.

  • As Earth moves in its orbit, astronomers are able to observe stars from two different positions.

  • Astronomers measure the parallax of nearby stars to determine their distance from Earth


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Properties of Stars

  • Astronomers classifystars by their color, size, and brightness. Other properties of stars are chemical composition and mass.

  • Color and Temperature – a stars color indicates the temperature of its’ surface.

  • The hottest stars appear blue

  • The cooler stars appear red

  • The spectrum of color in a star is from blues to greens to yellows and reds.

The_Color_of_Stars


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Brightness

  • The brightness of a star as viewed from Earth is dependent on many factors such as color intensity and distance.

  • Apparent Brightness – is the brightness of a star as it appears from Earth.

  • The apparent brightness decreases as its distance from you increases

  • Absolute Brightness – is how bright a star really is. The absolute brightness is a characteristic of the star and is not dependent on its distance from Earth.


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Composition

  • Each star has its own spectrum.

  • Most stars have a chemical makeup that is similar to the sun, with hydrogen and helium together making up to 96 to 99.9 % of a star’s mass.


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How Stars Form

  • A nebula is a large cloud of gas and dust spread out over a large volume of space.

  • Some nebulas are glowing clouds lit from within by bright stars.

  • A star is formed when a contacting cloud of gas and dust becomes so dense and hot that nuclear fusion begins.

How_Stars_Form


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Life Cycles of Stars

  • Adult Stars – A star’s mass determines the star’s place on the main sequence and how long it will stay.

  • The amount of gas and dust available when a star forms determines the mass of each young star.

  • The larger the star the more energy produce.

  • Since blue stars burn brightly, they use up their fuel quickly and are short lived.

The_Life_Cycle_of_Stars.asf


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The Death of a Star

  • The dwindling supply of fuel in a star’s core leads to the star’s death as a white dwarf, neutron star, or black hole.

Dying_Stars_and_Conclusion.asf


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Groups of Stars

  • Astronomers have determined that more than half of all stars are members of star systems.

  • There are three basic kinds of star clusters: open clusters, associations, and globular clusters.

  • Astronomers classify galaxies into four main types: spiral, barred-spiral, elliptical, and irregular.


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Expanding Universe

  • The observed red shift in the spectra of galaxies shows that the universe is expanding.

  • Astronomers theorize that the universe came into being in an event called the big bang.

  • Dark matter can only be detected by observing its gravitational effects on visible matter.

Beyond_the_Milky_Way_and_Back_Into_Time.asf

Spin_Around_the_Solar_System__A__Look_to_the_Stars


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