The Sky

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The Sky
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The Sky

• Constellations - Patterns of stars
• There are 88 constellations in the night time
  sky.

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The Sky

• The Greek alphabet is used to signify the
  brightness of a star in a constellation
• Betelgeuse (Beetle Juice) appears to be the
  brightest star in the constellation Orion. We
  would label Betelgeuse alpha Orionis, or ?
  Orionis.

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The Sky
North celestial pole - points to Polaris, the
north star.

• Celestial sphere model of the sky above us
• The ecliptic is the path the sun takes in the
  sky.
• The highest point on the ecliptic the sun reaches
  is the summer solstice. The lowest point is the
  winter solstice.

Stars are on the surface of the sphere.
Ecliptic
Celestial equator
South celestial pole
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The Sky

• The summer solstice occurs on June 21 and is, in
  the northern hemisphere, the day with the
  longest amount of daylight.
• The winter solstice occurs on December 21 and is
  the day with the shortest amount of daylight.

Summer solstice
Winter solstice
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The Sky
Autumnal equinox

• The equinoxes occur at the intersection points
  between the ecliptic and the celestial equator.
  Both days have equal light and darkness.
• Vernal equinox occurs in the spring on March 21
• Autumnal equinox occurs in the fall on September
  21

0h, 0min Vernal equinox
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The Sky

• Constellations that fall on the ecliptic are
  called the signs of the Zodiac.
•  We recognize 12 but there are actually 13
  constellations that fall on the ecliptic.
•  The thirteenth constellation on the zodiac is
  Ophiuchus (o fee' a cus)

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The Sky

• Precession is the slow change in direction of the
  Earths rotation axis due to its spin.
• The Earth is a very precise natural top.
• Circumpolar constellations are those
  constellations that never rise or set.

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The Sky

• We can find constellations on the celestial
  sphere by using coordinates. We use right
  ascension and declination.
• Right ascension is measured in hours, minutes and
  seconds. The Earth rotates through 360 degrees in
  24 hours.
• Declination is measured in degrees from the
  equator.
• The notation is as follows
• RA 4h33m (right ascension)
• dec 7?24' (declination)

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The Sky
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The Sky

• Seasons occur because the Earth is tilted 23
  1/2.
• The Earth is closest to the Sun in January.
• The Earth is farthest from the Sun in July.
• The distance to the Sun does not determine the
  seasons.

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The Cycles of the Moon

• Phases of the Moon
• Waxing phases
• Crescent
• Quarter
• Gibbous
• Waning phases
• Crescent
• Quarter
• Gibbous

• Full moon
• New moon

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The Cycles of the Moon

• Tides
• 2 High tides per day
• 2 Low tides per day

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The Cycles of the Moon

• Neap tide

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The Cycles of the Moon

• Spring tide

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The Cycles of the Moon

• Inner shadow is the umbra
• Outer shadow is the penumbra

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The Cycles of the Moon

• Lunar eclipses
• Total
• Coppery in color
• Partial
• Partially in umbra

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The Cycles of the Moon

• Solar Eclipses
• Total
• Umbra
• Diamond ring effect
• Partial
• Partially in umbra
• Annular
• penumbra