Lecture 5 The Night Sky

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Lecture 5 The Night Sky

• What is the connection between whats in the book
  and whats in the sky?

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We will discuss many types of objects lets see
them too

• Examples
• Red Supergiants (Antares)
• Population II Stars (Arcturus)
• Galaxies (M81)
• Basic astronomical phenomena known since
  antiquity
• First, we need a system to describe the sky

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First reference system the Horizon System

• Two coordinates altitude and azimuth

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In Horizon System, we see motions in the sky

• The Sun rises in the east, reaches highest
  altitude angle due south, sets in the west
• When the Sun sets, it gets dark and we see the
  stars and planets
• The Moon
• The Moon rises at a different time each night and
  is seen against a different constellation
• The constellations in the evening sky are
  different in different seasons

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Question for the audience

• What is going on to cause this east-to-west
  motion of all objects, rising in east and setting
  in west?

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Seasonal differences in the night sky go out
tonight at 10PM

• Constellations Bootes almost overhead
• Constellation Leo in the west
• Bright star Vega low in the east
• Constellation of Virgo in the south
• Constellation of Scorpius (with bright star
  Antares) low in southeast.
• Check it out with the help of the SC1 chart!

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Go out again at 10PM in mid-September

• Scorpius (and Antares) will be due south, to
  south-west
• The constellation Aquila (bright star Altair)
  will be in southeast
• Bright star Vega straight overhead
• Arcturus and Bootes way over in the west
• Come back in February, more changes still

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Question What causes this phenomenon of the
Parade of the Constellations?
Demonstration, more next time