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# 8th Grade Chapter 1 Lesson 4

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• 1. 8 th Grade Chapter 1 Lesson 4 Pgs. 27-32 For Student Use Only
• 2. Star Magnitude
• Star Appearance: Some stars appear brighter than other stars
• Apparent Magnitude- the brightness of a star as it appears to an observer on Earth.
• Depends on 2 things:
• Actual Brightness
• Distance from the earth
• 3. Star Magnitude
• Hipparchus developed the system for classifying stars based on their brightness.
• First Magnitude Stars= Brightest
• Sixth Magnitude Stars= Faintest
• The lower the apparent magnitude- the brighter the star. (NOTE: Stars can go negative on the scale)
• 4. Star Magnitude
• Apparent Magnitude measures the brightness of stars, but we first must know the distance of the star.
• Apparent Magnitude is calculated by the inverse square law .
• Inverse Square Law states: the brightness of a star varies inversely as the square of the distance from the star.
• 5. Star Magnitude
• We can also calculate how bright stars really are ( absolute magnitude ) by using their distance and apparent magnitude.
• Absolute Magnitude : The brightness of the star if all stars were the same distance from Earth. Astronomers use the distance of 10 parsecs from Earth.
• Absolute Magnitude depends on 2 things:
• Surface Temperature
• Size
• 6. Star Colors
• Surface Temperature causes different colors in stars.
• Red Stars- cooler stars
• Yellow stars- warmer stars
• White stars- hot
• Blue-white stars= hottest
• 7. Star Colors
• Although some stars are hotter than others, cooler stars can outshine hot stars because of bulk.
• Size of stars help them to shine brighter.
• Bigger cooler stars can outshine smaller hot stars.
• 8. Star Colors
• Giants and Dwarfs:
• GIANTS : These stars are extremely bright for how cool they are. That is because they are BIG!
• Dwarfs : Star that are smaller.
• White dwarfs are stars that are smaller and dimmer than average stars.
• 9. Stars
• Some stars are binary stars :
• 2 stars that orbit together are a double star.
• Sirius and Sirius B (The Pup) are binary stars.
• Optical doubles: can be confused with binary stars. These are stars that appear to be close together from Earth, but are actually far apart.
• 10. Stars
• Stars also can occur in groupings called star clusters .
• Globular Cluster: groups of stars that travel together
• 11. Stars
• Star Explosions:
• Occasionally stars flare up and become very bright this is call a NOVA .
• During a NOVA a star will become very bright but eventually return to its normal size
• Occasionally stars also flare up so large that they become SUPERNOVAS!
• A SUPERNOVA is an explosion of a star.