Transcript Astronomy - Red Hook Central School Dst

Astronomy
Contents of the universe
We live in the solar system.
Earth orbits the sun every yr in
elliptical orbit.
Distance Earth to sun 1 AU
Birth of the Solar System
Solar system born ~4.5 BYA
2 min
http://www.youtube.com/watch?v=
qfdDWdZcpOw
Our Solar System
planets/moons/asteriods
Asteroid Belt mars-Jupiter
Icy Comets
-All orbit the sun
-very elliptical orbits
Solar system is part of the
milky way galaxy. Orion Arm.
The galaxy revolves around
black hole. Sun revolution ~ 250
million y.
Galaxies –large aggregates of stars, gas,
& dust containing ~ 100 billion (1011)
stars ranging in diameter from 1,500 to
300,000 light-years across. Orbit central
point. Av distance btw stars 10 ly.
Stars can form stellar clusters w/i
galaxies – smaller groups of stars held
by gravity. ~ 1000’s of stars.
Constellations – star groups not
necessarily near each other.
Galaxies form groups too.
Galactic Clusters
• Nearest cluster = Virgo cluster
It’s a long way btw stars.
Use Light Years LY
Calculate the d light travels in 1 yr.
1 LY = 9.46 x 10
15
m.
Relative Distances
Universe
~1.5 x 1026 m
15 Billion LY
Between
galactic clusters
~10
Betw galaxies
~106 LY
Local group (20 gal)
radius
2 x 106 LY
Milky Way
8
LY
105 LY dia, 104 LY thick
10 LY btw stars
Powers of 10 Film
http://www.youtube.com/watch?v=tnhken4_-A0
Earth’s Rotation makes
stars appear to rotate on
fixed sphere.
Rotation is around Polaris on
24 h cycle.
Sun/planets wander through
stellar backdrop.
From Earth Stars Appear to be
embedded in sphere.
Stars rotate around Polaris
24 hr cycle rise east set west
Stars appear fixed on sphere relative to
each other.
http://www.youtube.com/watch?v=JCr_Pz4h2Bw
Planetary Motion Wanderer &
Retrograde
Hwk Sheet: Intro to
Astrophysics