Stars

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Stars
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Constellations

• A group of stars that appears to form a pattern
  in the sky

AQUARIUS
Virgo
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Constellations -

• total of 88 different constellations can be seen
  in the N and S hemispheres
• As you move north you can see more stars.

Andromeda
Aries
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Constellations-

• Ursa Major - (Big Bear) is the most famous
  constellation

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Constellations-

• The Big Dipper is part of Ursa Major

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Constellations-

• Two stars of Ursa Major are used to find the
  North star- Polaris-(pole star)

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Polaris
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Constellations-

• Polaris is part of Ursa Minor (the little dipper)

Ursa Minor
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Constellations-

• As the earth rotates on its axis the
  constellations move.
• They rotate around Polaris counter clockwise.
• The earths axis points toward the N. Star

Pg. 617 (fig. 28.2)
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Constellations-
Orion in Winter

• Some constellations can only be seen during
  specific seasons
• This is due to earths rotation around sun and
  tilt of the earth

Lyra in summer
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Circumpolar Rotation around Polaris
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What happens as you travel North?

• The number of circumpolar stars visible,
  increases as the observer moves North

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Can you tell what constellations these are?
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Ursa Major
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Lyra
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Orion
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Aquarius
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Gemini
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Stars- How far to a star?

• Closest Star Sun
• 93,000,000 miles 1 astronomical
  unit
• Next closest star
• Proxima Centauri
• 25 trillion miles
• 2.5 x 10 13
• 4.2 light years

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Light year-

• Distance that light travels in one year
• 5,900,000,000,000 miles
• Polaris- 680 LY
• Betelgeuse (red supergiant ) is 490 LY

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Properties of Stars

• Our Sun-
• Diameter-
• 855600 miles
• 110x earth
• Density
• 1.4 x density H20
• Mass
• 300,000x earth

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How does our sun compare?

• Diameter-
• average
• Density-
• mid to high
• Mass-
• Other stars range from 1/100th to 50x our sun

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How do we size up?
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Wow! Jupiter is BIG
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Our sun is REALLY BIG!
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Guess Not!
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We are REALLY SMALL! I feel so insignificant!
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Color?
Depends on surface temperature
cool
Hot- 30,000 C
Medium- our sun (5500C)
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Classification of stars
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Composition of Stars-
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• How can we tell?
• Our sun-
• Hydrogen (70)
• Helium (28)
• No 2 stars have the same spectra (like a
  fingerprint)

You know this!
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-Brightness-

• Apparent Magnitude-
• how bright a star appears to earth observer.
• Depends on
• Distance from us
• what is between us
• true brightness

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Brightness-

• Luminosity-
• True brightness
• Depends on(2 things)
• Size -if same size, blue is more luminous
• Temp.- if same temp., bigger is more luminous

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Absolute Magnitude-
Rigel- foot of Orion 40,000 suns Blue Super
Giant

• How stars would appear if they were all the same
  distance from earth.
• All stars place 32.6 LY from the sun
• Our sun abs. Mag 4.8
• Negative is brighter

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