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Galaxies and Distance

Galaxies and Distance. Understand the structure of galaxies. Explain the shape and location of our galaxy. Understand the use of space units for distance. KEY WORDS Galaxy Star Cluster Light-years Astronomical Units Parsecs. Galaxies

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Galaxies and Distance

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  1. Galaxies and Distance

  2. Understand the structure of galaxies. • Explain the shape and location of our galaxy. • Understand the use of space units for distance. KEY WORDS Galaxy Star Cluster Light-years Astronomical Units Parsecs

  3. Galaxies • Huge collections of gas, dust and billions of stars and planets. • Force of gravity attracts the stars in a galaxy to each other. • Many shapes: spiral, elliptical, and irregular. • They are constantly in motion.

  4. Astronomers see galaxies as far away as telescopes permit.

  5. Milky Way galaxy: • Contains 400 billion stars. • Disc-shaped, with spiral arms – spiral galaxy. • We are on one of the arms. • Has a thicker Central Bulge. • Rotates around the bulge.

  6. Unusual things Astronomers are researching: • Some galaxies appear to be colliding and recombining. • Some galaxies emit far moreenergy than average. • Quasars: • - Look like a small star. • - Emit up to 100x more energy than our galaxy. • - They emit radio waves.

  7. Star Clusters • Contain 10 to a million stars (too small to be galaxies). • Stars are fairly close and travel together. • The Pleiades (near Orion) is a star cluster. • – you can see six or seven • stars with your naked eye.

  8. Distances in Space

  9. Scientific Notation • Use scientific notation to express very large or very small numbers. • Power of 10 equals the number of places the decimal was moved – negative means small. • 32 000 000 is 3.2 x107 • 0.0000000055 is 5.5 x10-9 • 2.6 x105 is 260 000 • 2.6 x10-5 is 0.000026

  10. Nearest star - 4.1x1013 km (41,000,000,000,000). • This star is Alpha Centari. • Light-year (LY): • Distance traveled by light in one year. • Light travels very fast – about 300,000 km/sec. • 9.46x1012 km /year – this is 1 light-year. • Alpha Centari is 4.3 light-years away.

  11. Distances can be deceiving. • Two stars look close, may actually be very far. • Light we see left that star many years ago - looking at what has already happened – past. Star or ObjectApprox. Distance (LY) Alpha Centari4.3 Sirius (brightest star) 8.8 Betelguese 700 Rigel 900 Most distant known galaxy 15,000,000,000

  12. Distances within solar systems: • Common to use Astronomical Unit (A.U.) • 1 A.U. = distance between the Earth and the Sun

  13. Sun - Earth: 1 AU = 1.5x108 km Sun - Pluto: ~ 40 AU Sun - Saturn: ~ 10 AU Sun - Jupiter: ~ 5 AU Sun - Mars: ~ 1.5 AU

  14. Other Units - parsec (pc) 1 parsec = 3.26 light years

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