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PG 15

PG 15. Put the following in scientific notation 3,457,000 .0000245 How many constellations are in Space?. Magnitude & Brightness (15). Hipparchus: 200-100 BCE, Greek astronomer. Classified 1000+ objects by brightness. 1st Class: Brightest objects. 6th Class: Dimmest objects.

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PG 15

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  1. PG 15 • Put the following in scientific notation • 3,457,000 • .0000245 • How many constellations are in Space?

  2. Magnitude & Brightness (15)

  3. Hipparchus: 200-100 BCE, Greek astronomer. • Classified 1000+ objects by brightness. • 1st Class: Brightest objects. • 6th Class: Dimmest objects. • System used today is a modified version called the magnitude scale.

  4. Magnitude • Measures the brightness of an object. • Dimmer objects = larger number. • Brighter objects = smaller number. -26 Sun -20.5 Milky Way Galaxy -13 Full Moon -4 Venus -2 Jupiter +1 Saturn +2 stars of Big Dipper +5 moons of Jupiter +6 Uranus +8 Neptune +8 farthest you can see with binoculars +11 Prx. Cent. +14 Pluto at its brightest +30 Hubble Deep Space Telescope

  5. Types of Magnitude • Apparent Magnitude: • Brightness as seen from earth. • Problem: • Distant objects appear fainter. • Nearer objects appear brighter.

  6. Absolute Magnitude: • Brightness an object if it were 32.6 light yearsfrom earth. • (10 parsecs) • Allows brightness to be compared without differences in distance. • Problem: Need to know an object’s distance from Earth.

  7. Using apparent magnitude to find absolute magnitude • β Crucis (or Mimosa) has an apparent magnitude of 1.25 and is 108 parsecs distant. What is its absolute magnitude? • M = m - 5 log(d/10) • M = 1.25 - 5 log(108/10) • M = 1.25 - 5 log(10.8) • M = 1.25 - 5.x 1.0334 • M = 1.25 - 5.1671 therefore: • M = -3.92

  8. Why is Absolute Magnitude important? • Brightness is directly related to an object’s size and temperature.

  9. Magnitude Venn Diagram (14) • Create a Venn Diagram comparing and contrasting Apparent and Absolute Magnitude. • Draw a picture to illustrate the difference between Apparent and Absolute Magnitude. • Write a level 1 or 2 question and its answer for each of the following ideas: • Hipparchus • Magnitude • Absolute Magnitude • Apparent Magnitude

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