CHAPTER 25: STARS AND GALAXIES

I. STARS

A. ADVANCEMENTS IN ASTRONOMY NICHOLAS COPERNICUS TYCHO BRAYE JOHANNES KEPLER GALILEO NEWTON

B. THE SUN THE ONLY STAR IN OUR SOLAR SYSTEM MADE MOSTLY OF HYDROGEN AND HELIUM MAKES UP 99.86% OF THE MATTER IN THE SOLAR SYSTEM *see board for drawing

C. STARS 1. BRIGHT, HOT SPHERES OF GAS 2. SOME STARS APPEAR BRIGHTER THAN OTHERS

C. STARS (cont.) The color of a star indicates its temperature. Astronomers study the composition of stars by observing their spectra (its visible light color break down).

1) MAIN SEQUENCE STARS BLUE 25,000-50,000 BLUE-WHITE 11,000-75,000 WHITE 6,000-7,500 YELLOW 5,000-6,000 ORANGE 3,500-5,000 RED 3,000-3,500 *All in degrees Celsius

2) VARIABLE STARS STARS THAT EXPAND AND CONTRACT (CAUSING THEM TO GIVE OFF DIFF. AMTS. OF LIGHT) MULTIPLE STAR SYSTEM

D. LIFE CYCLE OF A STAR NEBULA MAIN SEQUENCE GIANTS WHITE DWARF NOVA NEUTRON STAR BLACK HOLE

*see diagram on board

II. GROUPINGS OF STARS

A. SOLAR SYSTEM B. CONSTELLATIONS C. GALAXIES (ELLIPTICAL, SPIRAL, & IRREGULAR) D. CLUSTERS E. UNIVERSE

F. THEORY OF RELATIVITY A THEORY OF THE NATURE OF SPACE, TIME, AND MATTER

2 E=mc E=energy m=mass c=speed of light (299,792,458 ² km/sec )

***Einstein showed that mass is never lost, but it may change to energy or a different form of matter

G. Big Bang Theory States that a fireball exploded billion years ago and matter and energy spread apart in all directions.

Big Bang Theory (cont.) Materials from the explosion formed clouds and from the clouds galaxies were formed during the next 1/2 billion years.

1st generation stars= the first stars to form in a galaxy 2nd generation stars= form from the clouds of gas and dust from dying 1st generation stars

H. SETI: Search for Extraterrestrial Intelligence Uses radio telescopes. They constantly listen to radio signals in hopes of receiving signals from outer space.

THE END