1. Astronomy
Earth Science

2. Astronomy Astronomy – Study of the Universe MAJOR PLAYERS (Greeks)
Aristotle – The Earth is round
Eratosthenes – Size of the Earth
Angle of sunlight differed by 7 degrees between Aswan and Alexandria
7 degrees = 1/50 of a circle
C = 39,400 km (actual = 40,075 km)
Hipparchus – Catalogued 850 stars

3. Astronomy Models of the Universe Geocentric (Early Greeks)
Geo – earth centric – center – Earth centered
Moon, Sun, Mercury, Venus, and Jupiter orbit Earth
All other stars remained in the same position
Known as the celestial sphere

4. Astronomy Models Heliocentric (Aristarchus)
Helio—sun centric—center  Sun centered
Earth and other planets orbit the Sun
Aristarchus used geometry to calculate the distance to the Sun and moon
Earth centered theory dominated Western thought for nearly 2,000 years.

5. Isaac Newton English physicist Developed the Laws of Motion
1st Law of Motion
An object in motion stays in motion unless acted upon by an outside force. An object at rest stays at rest unless acted upon by an outside force.

6. 2nd Law of Motion 3rd Law of Motion
The acceleration of an object is in the same direction as the net force on the object
F = ma
3rd Law of Motion
For every action there is an equal and opposite reaction

7. Johannes Kepler Kepler developed the Laws of Planetary Motion
The orbit of every planet is an ellipse.
A line joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit.
Longer orbits have longer periods, and the speed of a planet in a larger orbit is lower than in a smaller orbit.
D3 = T2 D= distance in AU T= period in years
1 Astronomical Unit = 93 million miles!
Distance from the Earth to Sun

8. Practice Problem
Calculate the period of Mercury if it is 0.39 AU away from the Sun.
D=0.39 AU
T=?
D3=T = T2
T = 0.24 years

9. Practice Problem
Calculate the distance Mercury is from the Sun if its period is 0.24 years.
D=?
T=0.24 years
D3=T2 D3 = 0.242
T = 0.39 AU

10. Formation of the Universe
It is believed that the Universe started 13.7 billion years ago as a massive explosion
The entire Universe was confined to a dense, hot, supermassive ball
But how do we know this?
All galaxies appear to be moving away from the Earth
Data indicates the universe is still expanding
Cosmic background radiation

11. Formation of a Galaxy
Astronomers have come up with multiple theories as to the formation of galaxies
One theory suggests that after the Big Bang millions of gas clouds (nebulae) and star clusters merged together
Note: Deep Field Image was taken in a spot of sky near the Big Dipper about the width of a dime 75 ft away.

12. We are here

14. Center of Galaxy
Milky Way galaxy is 100,000 light years across and 3,000 light years thick
Light travels 10,000,000,000,000 kilometers in one year

15. Star Formation
Stars are born in dark, cool interstellar clouds called a nebula.
These clouds begin to contract and gravity begins to pull every particle to the center
A protostar is in the beginning stages of formation and lasts around 1 million years
Once the internal temperature reaches 10 million Kelvin, nuclear fusion begins

16. Star Formation Main Sequence Red Giants
A hot blue star will deplete their hydrogen fuel in a few million years
A yellow star (our Sun) may last for 10 billion years
Red Giants
The star expands, the outer atmosphere expands and the core shrinks

17. Star Formation White Dwarfs
Once the star has depleted all of its fuel it collapses under its own gravity
AKA a supernova
Sometimes a star will release its outer layer of gas creating a planetary nebula

18. Star Formation Supernovas and Neutron Stars
A neutron star is a small, massive star that remains after a supernova
A supernova occurs when the outer layer of the star is ejected and the star collapses

19. Hertzsprung-Russell Diagram
A star’s brightness as it appears from Earth is the apparent magnitude.
Three factors:
How big it is
How hot it is
How far away it is
The absolute magnitude is how bright the star actually is
Two stars of the same absolute magnitude usually do not have the same apparent magnitude because one may be much farther from us than the other

20. Hertzsprung-Russell Diagram
Astronomers determine what magnitude the stars would have if they were at a standard distance of 32.6 light-years.
A light year is the distance light travels in one year
The Sun: apparent magnitude of __-26.7__, absolute magnitude of __5.0_.
The more negative, the brighter; the more positive, the dimmer.

22. Solar System Formation
Current theory suggests the solar system was formed from a rotating disk of dust and gases
Called the Nebular Theory
A nebula is a collection of gas and dust
Most matter in the nebula collected at the center

24. Solar System Formation
The first bodies of the solar system were planetesimals
Eventually built up enough mass to exert a gravitational pull
Animation: (View on your own)

25. Terrestrial Planets The inner planets are small and rocky Mercury
Absorbs 94% of the sunlight
Many craters
Venus
Thick clouds help reflect sunlight
Surface temp. = 475 degrees Celsius
Atmosphere is 97% Carbon dioxide

26. Terrestrial Planets Mars Surface is mostly Iron oxide (rust)
Atmosphere is mostly carbon dioxide
Some evidence of water

27. Jovian Planets
The outer planets are large…many times the diameter of earth
Composed of a variety of gases
Most have a rocky core
All have ring systems
Jupiter, Saturn, Uranus, Neptune

28. Galileo
Discovered four moons orbiting Jupiter

29. Galileo Planets are circular disks and not just points of light
Venus has phases just like the moon

30. Galileo
The moon’s surface is not smooth

31. Galileo
The Sun has sunspots (areas of the sun with “cooler” temperatures)

32. Asteroid Belts Two belts Belt between Mars and Jupiter (failed planet)
Kuiper Belt (International Astronomical Union)
Region of the Solar System beyond Neptune
Pluto resides in this belt
Irregular orbit
Many thousands of objects

35. Refracting Telescopes
Galileo’s first telescope (30x)
Uses lenses to bend or refract light

36. Reflecting Telescope Newton built the first reflecting telescope
Use a concave mirror that focuses light in front of the mirror

37. Radio Telescopes Detect radio waves from distant objects
Can use during the daytime or inclement weather
Detect collisions of galaxies, black holes, binary stars, etc…