GALAXIES OF STARS & OUR UNIVERSE

OUR SOLAR SYSTEM SEE esrt PG 15 - 8 Planets - Meteors Asteroids - Kuiper Belt Inner terrestrial planets - Outer Gas giants

Asteroid Belt Rocky bodies that orbit the sun between Mars and Jupiter

Kuiper Belt and The Oort Cloud. Kuiper Belt – thick belt of debris left over from formation of outer planets. Oort Cloud - a vast shell of icy objects (i.e.comets) surrounding the solar system.

The Milky Way A galaxy is a huge body of stars and other matter in space. Milky Way shows: - Prominent spiral arms - Central galactic bulge - Location of Sun - A member of a small cluster of galaxies called the Local Group. - Andromeda is the nearest galaxy to us.

The Size of Our Universe Light year – distance light travels in one year. 10 trillion km Our universe is 25 billion light years in diameter and 13-15 billion years old. Closest star to us is Proxima Centauri – 4.22 light years away. When you look at very distant objects in the universe you are looking back in time. The speed of light travels so fast it could circle the Earth 7 x in 1 second. Light takes about 1.5 seconds to get to the moon. Scale l----------------------------------------------l ‹--------------100,000 light years ---------› Speed of light: 1,079,252,848.8 km/h = (299,792,458 m/s) = 186,282.397 miles/sec

Caption: Illustration showing the creation and expansion of the universe. Credit: NASA

The Big Bang Theory Proposed by George LeMaitre (a Roman Catholic priest) in 1927 Says the universe began from a primordial hot and dense state which exploded out into space. How do we know it is expanding? Evidence provided initially by Edwin Hubble in 1929. - Red Shift Also, Background (cosmic microwave) Radiation from space. (1964)

universe-review.ca/I02-08-redshift.gif

Light Spectra and the Doppler Effect A spectroscope is used to separate light into its component colors (ex. Prism) Dark lines within specific colors are characteristic of spectra of light given off by stars. A way to measure a stars motion is the Doppler effect. Waves of light (or sound) emitted by a moving object change their length according to whether the object is moving toward or away from the observer.

Light waves from an approaching star are shortened – they are shifted toward the blue end of the spectrum. Light from a receding star is shifted in the other direction – it is red-shifted. By measuring the amount of shift, the speed of the star can be calculated. Therefore the more distant the galaxy, the greater the red-shift shown. RED SHIFT – AWAY BLUE SHIFT - TOWARDS

So many questions… What is the fate of our universe? Scientists are trying to answer this and many other questions posed by our ever expanding wealth of knowledge. There is still so much to learn…