What is a star? - body of gasses that give off “tons of” energy (light & heat) - clusters = those little specks in the sky that we see may really be more than one star….

PHYSICAL PROPERTIES OF STARS -- 1. Differ in SIZE 2. Differ in COLOR 3. Differ in D I S T A N C E from us 4. Differ in COMPOSITION 5. Differ in BRIGHTNESS

Our Sun in considered an average-sized star! The diameter of our sun is about 109 times the diameter of the Earth! It has been burning for about 5 billion years. It is only middle-aged. It will burn for about 5 billion more years!! X 109 =

How Are Star Sizes Like Celebrities? Sometimes the larger the star, the shorter the life span. This is like the bigger the celebrity (more famous), the shorter their life span! Ex. James Dean, Chris Farley

Function of how LARGE the star is, how OLD it is, and how FAR AWAY. BRIGHTNESS Function of how LARGE the star is, how OLD it is, and how FAR AWAY.

THE STAR IS TO OBSERVERS ON EARTH APPARENT MAGNITUDE - IS HOW BRIGHT THE STAR IS TO OBSERVERS ON EARTH

Size and closeness can effect apparent magnitude the brightness how WE see it the brightest star in a constellation is called the ‘alpha’, then ‘beta’, etc… Size and closeness can effect apparent magnitude

Distance to Stars Our Sun is the closest star at 93 million miles distance. Next is Alpha Centauri at a distance of 4.27 light years. A light year is 5.88 trillion miles.

Stellar Parallax Parallax = shift in angle that occurs when a nearby object is seen against a distant backdrop from two different perspectives

is a star’s apparent brightness if we could position the star 32 is a star’s apparent brightness if we could position the star 32.6 light-years away (the distance that is the furthest star we can see from Earth) Absolute Magnitude

THERE ARE DIFFERENT WAYS TO MEASURE STAR BRIGHTNESS :

-depends on SIZE and TEMPERATURE

COLOR Yes, stars have different colors! The temperature of the star determines its color.

Star Color if you look close enough…you’ll see colors…. blue = HOT = 17,000o red = not so hot = 1,700o Our sun = orange ~ 10,000o

What are the Star Colors? Blue White Yellow Orange Red Hottest Coolest

Star patterns : 1000’s of years of observations - want to organize what they saw constellations = they are named after animals, greek gods and legendary heroes there are 88 named constellations

What should be the brightest star for us? THE SUN! it’s the closest - so it should appear the brightest BUT - it’s just average in reality ABSOLUTE magnitude = real brightness

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R U S E L D I A G M H e r t z s p r u n g

C. 1-2% heavy elements like IRON, TITANIUM, CALCIUM & SODIUM Composition A. 70% HYDROGEN B. 28 % HELIUM C. 1-2% heavy elements like IRON, TITANIUM, CALCIUM & SODIUM D. 2 % other heavy elements

The light from glowing elements can be analyzed with a Spectroscope Every element has its own characteristic color when made to emit light. The light from glowing elements can be analyzed with a Spectroscope Spectrum

Viewed from these two different locations, a nearby star would appear to shift position with respect to more distant stars The bigger the shift, the closer the start is to earth