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CH 25…The Stahz

CH 25…The Stahz. Constellations – regions of the sky, but often referred to as star patterns. 88 constellations All stars in group not at same distance Every star is part of a constellation. Characteristics of Starz. Appear to move around Earth in a circle, around the North Star

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CH 25…The Stahz

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  1. CH 25…The Stahz • Constellations – regions of the sky, but often referred to as star patterns. • 88 constellations • All stars in group not at same distance • Every star is part of a constellation

  2. Characteristics of Starz • Appear to move around Earth in a circle, around the North Star • Color – is from the star’s temp. - blue = hottest, 30,000° - red = coolest, 5000°

  3. Each star is assigned a letter based on its temperature • ( O) Blue • ( B ) Blue white • ( A ) White • ( F ) Yellow white • ( G ) Yellow • ( K ) Orange • ( M ) Red • Remember it with this anagram: • Oh Be A Fine Girl/Guy Kiss Me.

  4. Star Mass • Binary Stars – 2 or more orbiting each other/together • used to find the mass of stars • more than 50% of stars occur in pairs, or more!

  5. Note: For stars of equal mass, the center of mass lies in the middle Note: A star twice as massive as its partner is twice as close to the center of mass. It therefore has a smaller orbit .

  6. Distances to Stars • Distance – only close stars can be measured directly by parallax. • Close stars move more against their backgrounds • Ex: finger and eye… • Light Year = the distancelight travels in a year…it’s far☺

  7. Star Brightness • Brightness = magnitude • Apparent Magnitude – how bright it appears, to us, now. • Absolute Magnitude – how bright the star really is. • 3 factors control how bright the star appears… • Distance, size, & temp

  8. Distance • Closer stars appear brighter Size • Bigger stars appear brighter Temperature • Hotter stars appear brighter

  9. Magnitudes are given numbers • Smaller numbers are brighter! • Negative numbers are even brighter!!

  10. The H-R Diagram • H-R = Hertzsprung – Russell • Shows the absolute magnitude vs surface temp. • Most fall into the main-sequence part of the diagram. This is where a star spends 90% of its life.

  11. 25.2 Star Evolution • How do we know??? • What would an alien be able to tell about earth life if he had only 1 day to spend on earth? • We have put together bits and pieces we see to make a whole picture…that works pretty well.

  12. Stars are born from a huge rotating cloud of gas, mostly hydrogen (92%). • The gas contracts, heats up, and spins = protostar. • Continues until the core reaches 10 million°. • Now fusion (turning hydrogen into helium) begins and releases tremendous energy…like huge amounts!!

  13. Fusion starts its time as a main sequence star • The star is in a delicate balance between fusion (trying to blow it up) and gravity (trying to squish it) • Little red stars live long • Big blue stars live short lives • When the fuel supply is gone it turns into a red giant. STOP…

  14. What Happens Next??? • There are 3 outcomes based on mass… • 1. low mass • 2. medium mass • 3. high mass

  15. Low Mass Stars • The red giant shrinks, sheds its shell = planetary nebula. • A small, hot star called a white dwarf is left • It cools off and dies.

  16. Medium Mass Stars • After the red giant phase the contracts and explodes = supernova. • Becomes a neutron star…made entirely of neutrons. • Sometimes they shoot out a radio beam and are called pulsars • A teaspoon full would weigh…

  17. High Mass Stars • Just like a medium mass, but a red supergiant forms. • It explodes, also, as a supernova, but forms a black hole instead☺

  18. Black Holes • The center is called a singularity and is infinitely small. • The edge is called the event horizon = the point of no return • Gravity so huge that even light cannot escape from it. • Spaghettification…uh oh spaghettio…..

  19. 25.3 The Universe • The Milky Way is our galaxy • It’s about 100,000 light years wide and 10,000 ly thick in the middle • Our solar system orbits the center of the galaxy every 200 million years

  20. Galaxy Types 1. Spiral – usually disk shaped with stars concentrated at the center. • Numerous variations • 30 % of galaxies • Barred has stars on bars • Young and old stars

  21. Taken in IR

  22. 1. Elliptical • Range from oval to round • 60 % of galaxies • Usually small • Mostly old stars

  23. 1. Irregular Galaxies • 10 % of galaxies • Mostly young stars

  24. The Expanding Universe • 1929 Edwin Hubble noticed that most galaxies had huge red shifts • Meant they were all moving away very fast • Farther galaxies were moving faster • Hubble’s Law – distance away is related to speed of galaxy

  25. The Big Bang • The red-shifts meant all galaxies were expanding from each other! • Figured that a long time ago they were all together. • Says that 13.7 billion years ago the entire universe was super dense and super hot, and the size of infinite smallness…wow!

  26. Big Bang Evidence and the Future of the Universe 1. Red shifts 2. The echo of the big bang • Cosmic background radiation is present in the amount they predicted What will the future hold for us?

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