Astronomy chapter 1, Section 2

1
Astronomy chapter 1, Section 2

• Diana Smith
• Astrolabe

2
Mapping the Stars

• Ancient cultures linked stars together in
  patterns which reflected the beliefs and legends
  of its people
• Now scientists know more about the stars and
  their distance and can now describe a stars
  precise position with numbers

3
Constellations

• Constellations are sections of the sky which
  contain recognizable star patterns
• Modern astronomers divide the sky into 88
  constellations which are recognized worldwide by
  a specific name

4
Draco and Orion

5
Seasonal Changes

• Constellations change from season to season
• Maps of the constellations are broken into the
  four seasons

6
Finding Stars

• Astrolabes can help measure the altitude of a
  star
• Altitude is the angle between the object and the
  horizon
• Zenith is an imaginary point in the sky directly
  above an observer .
• A zenith always has an altitude of 90 degrees
• The horizon is the line where the sky and the
  earth appear to meet.

7
Describing a Stars Position

• Celestial sphere an imaginary sphere
  surrounding the earth and is used to map stars in
  a way similar to mapping latitude and longitude
• Celestial equator is created by extending earths
  equator into space

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A Stars Position

• Right Ascension hours eastward from the vernal
  equinox (spring equinox)
• Declination degrees north or south of the
  celestial equator
• Ecliptic the apparent path the sun takes across
  the celestial sphere as seen from earth

9
Altitude and Azimuth

10
Circumpolar stars

• Stars that can be seen at all times of the year
  and at all times of the night are circumpolar.
• They are found near the poles

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12
Size and Scale of the Universe

• Stars are so distant that their distance is
  measured in light years.
• A light year is the distance that light can
  travel in a year.
• A light year is equal to about 9.46 trillion
  kilometers

13
Size of the Universe

• Scientists still do not agree on the size of the
  universe
• New information is gathered daily
• The farthest objects we can observe are at least
  10 billion light years away.