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The Universe. Viewing the Night Sky Clear view of the horizon Stay away from ambient light, houses, & trees A good star chart Telescope or binoculars A good imagination Is that a planet or a star?. The Universe. Star Brightness or Magnitude What determines a star’s magnitude? Distance
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The Universe • Viewing the Night Sky • Clear view of the horizon • Stay away from ambient light, houses, & trees • A good star chart • Telescope or binoculars • A good imagination • Is that a planet or a star?
The Universe • Star Brightness or Magnitude • What determines a star’s magnitude? • Distance • Light year • Distance light will travel in one year • 186,000 mi./sec. • Size • Actual amount of light being emitted
The Universe • Two classification scales • Apparent Magnitude • Based on what you see from Earth • Table 14.1 (p. 390) • Range • Sun: -26 • Human eye limit: +6 • Telescope (a big one): +26
The Universe • Absolute Magnitude • A stars “real brightness” • Luminosity • Standard distance • 32.6 ly • 1 sec. of parallax shift
The Universe • Temperature & Color of stars • Range • Blue – 30,000 – 80,000 K • Yellow – 5,000 – 6,000 K (Sun) • Red – 2,000 – 3,500 K • Classification based on temperature & color • O, B, A, F, G, K, M • Spectral type • Hertzsprung-Russell Diagram (Fig. 14.8) • Absolute magnitude and spectral type • Life cycle of a star
The Universe • Life Cycle of a Star • Proto Star Stage • Forms from the gasses of interstellar space • H & He • Fusion begins • Gravitational attraction of particles • Temperature & pressure rises
The Universe • Main Sequence Stage • Star continues to grow in mass & brightness • Range of spectral type • Red Giant Stage • Star begins to cool • Return to Main Sequence • The End • Supernova • Massive release of energy • A star gives back
The Universe • Galaxies • Milky Way • Spiral • The Beginning • The Big Bang • Proof of an expanding Universe • Edwin Hubble • Spectral shift • Red shift