Stars Constellations n A group of stars that

Stars

Constellations n A group of stars that appears to form a pattern in the sky Virgo AQUARIUS

Constellations total of 88 different constellations can be seen in the N and S hemispheres n As you move north you can see more stars. n Andromeda Aries

Constellationsn Ursa Major - (Big Bear) is the most famous constellation

Constellationsn The Big Dipper is part of Ursa Major

Constellationsn Two stars of Polaris Ursa Major are used to find the North star- Polaris? 1&2 (pole star)

Constellations- n Polaris is part of Ursa Minor (the little dipper) Ursa Minor

Constellationsn n n As the earth rotates on its axis the constellations move. They rotate around Polaris counter clockwise. The earth’s axis points toward the N. Star Pg. 617 (fig. 28. 2)

Orion in Winter Constellationsn n Some constellations can only be seen during specific seasons This is due to earth’s rotation around sun and tilt of the earth Lyra in summer ? 3, 4&5

Circumpolar Rotation around Polaris

What happens as you travel North? n The number of circumpolar stars visible, increases as the observer moves North

Can you tell what constellations these are?

? 6 Ursa Major

? 7 Lyra

? 8 Orion

Aquarius

Gemini

Stars- How far to a star? n n Closest Star = Sun 93, 000 miles = 1 astronomical unit Next closest star u Proxima Centauri u 25 trillion miles t 2. 5 x 10 13 u 4. 2 light years

Light yearn n Distance that light travels in one year 5, 900, 000, 000 miles Polaris- 680 LY Betelgeuse (red supergiant ) is 490 LY ? 9

Properties of Stars n Our Sunu Diametert 855600 miles t 110 x earth u Density t 1. 4 x density H 20 u Mass t 300, 000 x earth

How does our sun compare? n n n Diameteru average Densityu mid to high Massu Other stars range from 1/100 th to 50 x our sun

How do we size up?

Wow! Jupiter is BIG

Our sun is REALLY BIG!

Guess Not!

We are REALLY SMALL! I feel so insignificant!

Color? Depends on surface temperature cool Hot- ~30, 000 ° C Medium- our sun (5500°C)

Green stars look white to us! Classification of stars

? 10 & 11 Composition of Starsn How can we tell? You know this! Spectroscopy! Our sunu Hydrogen (70%) u Helium (28%) n No 2 stars have the same spectra (like a fingerprint) n

-Brightnessn Apparent Magnitudeu how bright a star appears to earth observer. u Depends on t Distance from us t what is between us t true brightness

Brightness- n Luminosityu True brightness u Depends on…(2 things) 1. Size -if same size, blue is more luminous 2. Temp. - if same temp. , bigger is more luminous

Absolute Magnitude. Rigel- foot of Orion 40, 000 suns “Blue Super Giant” n n How stars would appear if they were all the same distance from earth. All stars place 32. 6 LY from the sun Our sun abs. Mag = 4. 8 Negative is brighter ? 12