E1 Introduction to the Universe NEW.ppt - MrSimonPorter

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E1 Introduction to the Universe NEW.ppt - MrSimonPorter Powered By Docstoc
					E1 – Introduction to the Universe
Let’s make a model!
The Solar System
Let’s answer some
questions! (“Planet
     patterns”)
                  Main points
•   Know the names of the planets!
•   They orbit in ellipses with the sun at one foci
•   Inner planets small and rocky
•   Outer planets large and mainly gas
•   Outer planets are much further from the sun
•   Asteroid belt between Mars and Jupiter
Comets
                   Comets
• Giant dirty snow balls (ice and dust) (diameter
  100m - 50 km?)
• Very elliptical orbits
• Short period (T < 200 yrs) and long period
  (could be thousands of years)
• Oort cloud
• Tail(s) always point away from the sun
• Evaporate as they get closer to the sun
            My address
11507 Meadow Lake Drive
Houston
Texas 77077
USA
            My address
11507 Meadow Lake Drive
Houston
Texas 77077
USA
Earth
            My address
11507 Meadow Lake Drive
Houston
Texas 77077
USA
Earth
Solar System
            My address
11507 Meadow Lake Drive
Houston
Texas 77077
USA
Earth
Solar System
Milky way
             My address
11507 Meadow Lake Drive
Houston
Texas 77077
USA
Earth
Solar System
Milky way
Local group
Universe
             My address
11507 Meadow Lake Drive
Houston
Texas 77077
USA
Earth
Solar System
Milky way
Local group
Universe
Galaxy
                   Galaxies
• A large collection of stars held together by
  their mutual gravity.
• Dwarf galaxies might have only a few million
  stars, many galaxies have hundreds of billions.
• The Universe has around 100 billion galaxies
       Astronomical unit (1 AU)
  An astronomical unit (AU) is the average
  distance of the earth from the sun which is
  150 million km




1 AU = 1.5 x 1011 metres
                  Light Year
                         Defined as the distance
                   travelled by light in one year




1 ly = 3 x 108 x 365 x 24 x 60 x 60 = 9.46 x 1015 m
Distance between stars in a galaxy
About one parsec (defined later)

One parsec is 3.26 light years
      Distance between galaxies
• 100 kpc for galaxies in clusters
• A few Mpc for galaxies in different clusters
                 Constellations
• The pattern of the stars
  remains the same from
  night to night (over the
  time of a life-time)
                                  Orion’s
• These patterns have             belt
  been labelled
  constellations
                 Constellations
• The constellations do not
  appear in the same place
• Over the period of one
  night they appear to
  rotate around the pole
  star
• Some stars rise above
  the horizon during the
  night, and some set
  behind it.
                Constellations
• This same movement is continued during the day. The
  sun rises in the east and sets in the west. Maximum
  height at midday (in the south in the Northern
  hemisphere.
              Constellations
• The constellations visible also depends on the
  time of year
         Constellation position
• The location of stars also varies slightly at
  different times of year due to the change in
  position of the earth.
                   Place to place
• The constellation you can see also depends on
  where you are              I’m on top of the world!




                                    I can’t see the pole star!
Constellations – line of sight effect
• The stars in a constellation only appear to be
  close
              Stellar clusters
• A group of stars that are physically near each
  other in space, formed from the same gas
  cloud.
Let’s read!
       Pages 487 to 492.

				
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posted:8/31/2012
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