Astronomy 114 710 pm Tom Burbine tburbinemtholyoke'edu

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Astronomy 1147-10 pmTom Burbinetburbine_at_mtholy
oke.edu
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Website

• http//www.mtholyoke.edu/courses/tburbine/ASTR114/
  
• Link is also on Ella

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Terminology for looking at the sky
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Angular size

• We measure distances in the sky using angles
• 180o in the observable sky

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Star positions change versus latitude
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Celestial Sphere
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Magnitude System
brightest asteroid
4 Vesta

• Brighter lower number

http//www.astronomynotes.com/starprop/appmag.gif
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• V magnitude Name
• -1.47 Sirius
• 0.12 Rigel
• 0.34 Procyon
• 0.58 Betelgeuse
• 0.71 Capella
• 0.85 Aldebaran
• 1.15 Pollux
• 1.96 Castor
• 2.01 Polaris
• 2.39 Gamma Cassiopeiae

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What is a constellation?
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Constellations

• People refer to constellations as a pattern of
  stars
• Astronomers refer to constellations as specific
  regions of the sky
• In 1928, the IAU (International Astronomical
  Union) decided there were 88 constellations
• Many of the constellation names go back thousands
  of years

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Constellations

• The constellations are totally imaginary things
  that poets, farmers and astronomers have made up
  over the past 6,000 years (and probably even
  more!).
• The real purpose for the constellations is to
  help us tell which stars are which, nothing more.

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What is this constellation?
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Orion
Bigger the star, the brighter it is
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Orion was the son of the god of the sea,
Poseidon and a great hunter. One story is that he
made an enemy of Hera who sent a scorpion to
sting him. Orion was restored to health by
Ophiuchus, the first doctor of medicine.
Another story is that Artemis was tricked by by
Apollo to shoot an arrow at Orion. When he
died, Poseidon asked Zeus to put him among the
stars.
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Ursa Major

• Ursa Major, the Great Bear, was identified with a
  bear by native American Indians of the
  Northeastern United States and the ancient
  Greeks.
• The name common in Britain, the Plough,seems to
  have a medieval origin,
• Another common name among northern European
  cultures is the Wain, a shortened form of wagon

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What are the constellations named after

• 14 men and women
• 9 birds
• 2 insects
• 19 land animals
• 10 water creatures
• 2 centaurs
• one head of hair
• a serpent
• a dragon
• a flying horse
• a river
• 29 inanimate objects

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• Originally considered part of Leos tail

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• Named after Queen Berenice II of Egypt, wife of
  Ptolemy III Euergetes (246 BC - 221 BC)
• Around 243 BC, the king undertook a dangerous
  expedition against the Syrians, who had murdered
  his sister.
• Berenice swore to the goddess Aphrodite to
  sacrifice her famous long hair if her husband
  returned safely.
• He did, she had her hair cut, and placed it in
  the goddess' temple.
• By the next morning, the hair had disappeared.
• To appease the furious king and queen (and save
  the lives of the temple priests), the court
  astronomer, Conon, announced that the offering
  had so pleased the goddess that she had placed it
  in the sky.
• He indicated a cluster of stars that at the time
  were identified as Leo's tail, but now have been
  called Berenice's Hair.

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Zodiac

• The zodiac is an imaginary belt in the heavens
  extending approximately 8 degrees on either side
  of the Sun's apparent path (the ecliptic), that
  includes the apparent paths of the Moon and the
  planets Mercury, Venus, Mars, Jupiter, Saturn,
  Uranus, and Neptune.

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Question

• Why do all the planets seem to follow the same
  path?

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Answer

• The planets, the Earth, and the Sun all tend to
  fall in the same plane called the ecliptic

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Why dont all the constellations have ancient
names?
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• Ancient cultures such as the Greeks and Egyptians
  could not see the constellations in the Southern
  Hemisphere

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Question

• Why is the path of the constellations on the
  zodiac not on the celestial equator?

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Answer

• The rotation axis of the Earth is inclined with
  respect to the ecliptic

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• Polaris is called the North Star
• Brightest star in the constellation Ursa Minor.
• 48th brightest star in the night sky
• It is very close to the north celestial pole,
  making it the current northern pole star.
• Polaris' altitude, or height above the horizon,
  is equal to an observer's latitude.

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Question

• How can do know that the sun is travelling along
  the zodiac since you cant see stars during the
  day?

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Answer

• One can however figure out where the sun is on
  the zodiac by noting which is the last
  constellation of the zodiac to rise ahead of the
  Sun or the first to set after it.

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Any Questions?
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Any Questions?