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Chapter 25: Beyond our Solar system

Chapter 25: Beyond our Solar system. Pages 700 - 721. Characteristics of Stars. Star color is an indication of temperature Very hot stars (30,000 K) emit high-energy, low wavelength radiation. What color do they appear? Blue

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Chapter 25: Beyond our Solar system

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  1. Chapter 25: Beyond our Solar system Pages 700 - 721

  2. Characteristics of Stars • Star color is an indication of temperature • Very hot stars (30,000 K) emit high-energy, low wavelength radiation. What color do they appear? • Blue • Middle or average temp. stars (5000 – 6000 K) appearYellowlike our sun • Cooler stars (< 5000 K) emit low-energy, large wavelength radiation. What color do they appear? • Red

  3. Mass of Stars • Difficult to calculate • Unless the star is part of a pair • Binary stars – two stars revolving around a common center of mass under their mutual gravitational attraction • More than 50% of stars occur in pairs or multiples • Stars of equal mass will be equidistant from the center of mass • If stars’ mass is not equal, the center of mass will be closer to the more massive of the two • If the sizes of their orbits are known mass can be calculated • Binary Sunset

  4. Measuring Distance to Stars • Stellar parallax – slight shifting in the apparent position of a nearby star due to the orbital motion of Earth • Thumb’s up demo • Nearest stars have largest parallax effect • Stellar Parallax Simulator • This method only works with stars that are relatively close to Earth (within 100 light-years) • Of the billions of stars in the Milky Way galaxy, only about 700 are within parallax range

  5. Distance to the Stars • 1,000 m = 1 km • 150,000,000 km = 1 AU = 93,000,000 miles • Distances between stars are so large we need an even bigger standard of measure • Light-year – the distance light travels in one year • 1 light-year = 9,500,000,000,000 km (9.5 trillion) • Proxima Centauri, our nearest stellar neighbor, is 4.3 light-years away • How far is that in km? • 40,850,000,000,000 km!!

  6. Stellar Brightness • The measure of a stars brightness is its magnitude • Apparent magnitude – a star’s brightness as it appears from Earth; affected by three factors • How big it is; larger = brighter • How hot it is; hotter = brighter • How far it is away; closer = brighter • Absolute magnitude – brightness of a star if it were viewed from 32.6 light-years; compares true brightness • Large negative numbers are bright, large positive numbers are dim • For our sun; • Apparent magnitude = -26.7 • Absolute magnitude = 5.0

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