1. Astronomers, Theories, and Galaxies!
Whirlpool Galaxy, M51
Sketch: 1845 (ground telescope)
Whirlpool Galaxy, M51
Hubble Telescope: 2001

2. History of Astronomy Ancient Greek philosopher named Aristotle
wrote about several scientific ideas
His ideas were accepted by Western Civilization
Believed the Universe was “Earth-centered” or “Geocentric”

3. The “Geocentric” Model
Earth Centered
States that everything in the universe orbited around Earth
Supporters : Aristotle, Ptolemy, the catholic church

4. Ptolemy (150 AD) Roman citizen that lived in Egypt
Worked as an astronomer
and a mathematician
Used mathematics to develop
models of the structure of the
Universe
His model was also Earth
centered or “Geocentric”

5. Nicolaus Copernicus (February 19, 1473 – May 24, 1543)
Religious man who was also an astronomer
First astronomer to formulate a Heliocentric model
“Heliocentric” model places the Sun as the center of the Universe.
Collected data when he made
observations of the sky

6. Copernicus’ Discoveries
1.Earth moved with a daily motion on its axis
2. Also moved with a yearly motion around a stationary sun.
Heliocentric (Greek)
Helios = Sun Centric= Center

7. The Heliocentric Model
Sun centered
Supporters: Copernicus, Galileo, Newton

8. Ptolemy’s Universe
Copernicus’ Universe

9. Galileo Galilei
Made improvements to the telescope which led to better observations
Galileo’s Model
Ptolemy’s Model
Beginning in 1610, Galileo began making observations of Venus and its phases.
The observations gave further evidence to support the heliocentric model by Copernicus. (100 yrs later)

10. Inner Planet Comparison (w/ Pluto – the former planet!)

11. Outer and Inner Planets

12. Our Star!

13. What goes up, must come down
The origin of the Big Bang theory can be credited to Edwin Hubble. Hubble made the observation that the universe is continuously expanding.
Therefore, if the universe is expanding… going back in time suggests that all matter came from one source!

14. THE BIG BANG THEORY 1. The universe may have began billions
of years ago with a big explosion.
2. The explosion of the big bang sent all matter moving apart.
3. Within fractions of a second, the universe grew from the size of a pin to 2000 times the size of the sun.

15. 4. After the explosion the universe would have been a dense swirling mass of elementary particles……
As matter cooled, hydrogen and helium gas formed.

16. 5. Matter began collecting in clumps and eventually formed into protostars.
6. Over one billion years after the initial explosion, the first stars would have been born.

17. According to the Big Bang model, the universe expanded from an extremely dense, hot state and continues to expand today.

18. Oscillating Theory
universe has gone through periods of expansion and contraction
the universe is currently in a period of expansion!

19. The oscillatory universe, originally derived by Alexander Friedman in 1922
suggests that the universe undergoes a series of oscillations
Each beginning with a big bang and ending with a big crunch.
After the big bang, the universe expands for a while before the gravitational attraction of matter causes it to collapse back in

20. Steady State Theory
Scientists first thought the universe was static and that its appearance has never changed.
This is called the Steady State Theory
In this theory, galaxies are not moving away from one another
New stars are being made from energy in the center of galaxies

21. What will happen to the universe in the future?
Open Universe Theory:
The universe will keep expanding forever.
Closed Universe or Big Crunch
Theory:
Gravity will pull the universe back together again into one object and start the process over again.

22. What is the main piece of evidence that supports the big bang theory?
Most of the stars and galaxies seen from Earth are showing a red shift in the spectrum of light being given off.

23. Edwin Hubble
Hubble noticed redshifts in the light from the galaxies, and concluded that galaxies are moving away from each other.
The Universe is expanding! 1929

24. Galaxies… Group of stars, dust, and gas held together by gravity
There are over 100 billion galaxies in the universe
We live in the Milky Way Galaxy
NGC 7331 is often referred to as "the Milky Way's twin."

25. Galaxies can be found in large groups called clusters

26. How Galaxies Are Classified?
In part by their shapes.
3 main types: Spiral, Irregular, Elliptical
Sombrero Galaxy: Spiral
Irregular: Magellanic Cloud
Elliptical: Most Common Type

27. Spiral Galaxies Looks like a pinwheel Lots of stars
Examples: Milky Way,
Andromeda

28. Sombrero Galaxy: Spiral

31. Elliptical Galaxy
Vary in shape from ball or ovals to flat disks – No arms!
Contains little dust and gas
Most common galaxy type

32. Irregular Galaxy Have no definite shape Made of mostly dust and gas
Are newer
galaxies….always
making lots of new
stars
Rare

33. Galaxies…

34. What kind of galaxy is this?

35. What kind of galaxy are these…?

36. What kind of galaxy is this?

37. What kind of galaxy are these?

38. 2. 5 million light-years away is the galaxy Andromeda
2.5 million light-years away is the galaxy Andromeda. It is the nearest galaxy to our own, the Milky Way.
The Andromeda Galaxy, M31

39. Light-Years Light-year = the distance light travels in one year
For example, Andromeda travels for 2 million years before it is visible to us on Earth.
Light travels at a speed of 186,000 miles/second (6 trillion miles/year)