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

2E=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 10-20 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