1. Greek Word Origins astron chroma geo helios kentron photo sphaira star
Meaning
Key Terms
astron
chroma
geo
helios
kentron
photo
sphaira
star
color
Earth
sun
near the center; central
light
sphere
astronomy, asteroid
chromosphere
geocentric, geology
heliocentric
geocentric, heliocentric
photosphere
photosphere, chromosphere

2. Section 1: Observing the Solar System
What are the geocentric and heliocentric systems?
How did Copernicus, Galileo, and Kepler contribute to our knowledge of the solar system?
What objects make up the solar system?

3. Greek Observations of the Sky
The Greeks noticed how patterns of stars, called constellations, kept the same shapes from night to night and year to year. Meanwhile, the planets seemed to wander among them. . .
Questions to class: Where’s the Big Dipper?
Answer: It’s Ursa Major (Great Bear). They might guess Ursa Minor (Little Dipper or Small Bear).
Show class how to locate Little Dipper and the North Star in the night sky using the Big Dipper.
Constellation figures Some common constellations

4. Geocentric System
Early Greek astronomers believed in a geocentric system which has the Earth at the center of the revolving planets and stars.
About A.D. 140, the Greek astronomer Ptolemy further developed the geocentric model. His model of the universe was widely accepted for the next 1,500 years until . . .

5. Ptolemy’s Complicated Model

6. The Copernican Revolution!
Most people, including scientists, at this time couldn’t accept that Earth was not the center of the universe. However, in 1543, the Polish astronomer Nicolaus Copernicus worked out the arrangement of the known planets and how they move around the sun. His findings revolutionized the science of astronomy.

7. The Copernican Revolution

8. Heliocentric System
In a heliocentric system, Earth and the other planets revolve around the sun.
In the 1600’s, Galileo Galilei used the newly invented telescope to make discoveries that supported the heliocentric model.

9. Galileo’s Evidence
Galileo found moons revolving around Jupiter and saw that Venus has phases like the moon. These findings further proved the heliocentric theory. However, due to his controversial teachings and books, he was found guilty of heresy, and was placed under house arrest by the Pope.

10. Galileo’s Discoveries

11. Motions of the Planets
For more than 20 years in the late 1500’s, Danish astronomer Tyco Brahe observed and recorded the positions of the planets. After Brahe’s death in 1601, his assistant, Johannes Kepler, used this data to develop three laws that describe the motions of the planets.

12. Tyco Bites the Dust

13. Kepler’s Three Laws of Planet Motion
First Law: The orbit of each planet in the solar system is an ellipse, an elongated circle (not a perfect circle as previously thought).
Second Law: Each planet moves faster
when it is closer to the sun and slower when
it is farther away.
Third Law: Planets closer to the sun orbit
faster than planets that are farther from the Sun. OR
“The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.”

14. Modern View of the Solar System
The planets vary greatly in size and appearance. They also differ in terms of mass, composition, axis tilt, and distance from the Sun. To measure the great distances in the solar system, scientists use astronomical units (AU). One AU equals Earth’s average distance from the sun (about 150 million km).

15. The Sun and Planets
Shown below are the average distances of the planets and Pluto (a dwarf planet) from the sun. The solar system also includes smaller objects, such as comets and asteroids.

16. Section 2: The Sun How does the sun produce energy?
What are the layers of the sun’s interior and the sun’s atmosphere?
What features form on or above the sun’s surface?

17. The Sun The sun is a huge ball of ionized gas
(or plasma) that accounts for 99.8%
of the solar system’s total mass.
It is about ¾ hyrdogen and ¼ helium, plus small amounts of other elements.
Due to its mass, its gravity is strong
enough the hold all the planets and
other distant objects in orbit.
Is the sun a planet? A moon? If not, then what is it?
It is a star!

18. Nuclear Fusion
The sun’s energy is produced through nuclear fusion. This is when two atomic nuclei collide and combine, forming a larger nucleus and releasing energy in the process. What elements do we start and end with?
Hydrogen & Helium

19. The Layers of the Sun
The sun has an interior and an atmosphere, each of which consists of three layers.

20. The Sun’s Interior
The sun’s interior consist of the core, the radiation zone, and the convection zone. Core: The sun’s energy is produced here by fusion since temperature and pressure are so high. Radiation Zone: Middle layer of sun’s interior where energy is transferred by radiation through tightly packed gases. Convection Zone: Outermost layer of sun’s interior where hot gases rise to surface and cooler gases sink by convection.

21. The Sun’s Atmosphere
The sun’s atmosphere includes the photosphere, the chromosphere and the corona.
Photosphere: The inner layer of the
sun’s atmosphere. It is the visible
surface of the sun (i.e. what you see).
Chromosphere: Thin, reddish layer of
sun’s atmosphere just outside of the
photosphere.
Corona: Outermost layer of the sun’s
atmosphere which appears as a white
halo around the sun. It means “crown”
in Latin.
When can we see the corona?
During a solar eclipse

22. Features on the Sun Prominences: Huge loops of reddish gas which
Sunspots: Areas of gas on the sun’s surface that are cooler than the surrounding gases. They seem to move across the surface, showing that the sun rotates just like the Earth. The number of sunspots varies in 11 year cycles.
Prominences: Huge loops of reddish gas which
often link sunspot regions. In the picture on the left,
the Earth is about the size of this dot  .
Solar Flares: Eruptions which send hot gases
and millions of joules of energy streaming out
into space at about ½ the speed of light.

23. Solar Wind
The corona extends out into space millions of kilometers until it thins into streams of electrically charged particles known as solar wind.
Solar flares can cause great increases
in the number of these particles that reach
Earth. They can damage satellites,
disrupting radio, TV and telephone signals.
However, at the poles, these particles can
enter our atmosphere, exciting gas particles
to create auroras.
Earth’s magnetosphere protects
us from these particles.

24. Aurora Explanation

25. Section 3: The Inner Planets
What characteristics do the inner planets have in common?
What are the main characteristics that distinguish each of the inner planets?

26. The Inner Planets
The four inner planets—Mercury, Venus, Earth and Mars—are similar in that they are small and dense and have rocky surfaces. They are often called the terrestrial planets, from the Latin word terra, which means “Earth.”
Mercury, Venus, Earth & Moon, and Mars
These are to scale regarding size, but not distances

27. The Inner Planets
The inner planets take up only a small part of the solar system. Notice the differences in rotation and revolution times.
Sizes and distances are not drawn to scale.

28. Earth’s Layers
Earth is unique in our solar system in having liquid water at its surface (about 70% of the Earth’s surface).
Earth has three main layers—a crust, a mantle, and a core.
Earth has enough gravity to hold on to most gases, like nitrogen and oxygen.
These gas make up our atmosphere
which extends more than 100 km above its surface.
Other planets have atmospheres too, but only Earth’s is rich in oxygen (necessary to support most life).

29. Mercury
Mercury is the smallest terrestrial planet and the planet closest to the sun. It is covered with impact craters.
Since it so small, it doesn’t have enough gravity to hold an atmosphere. Therefore, its temperature varies greatly, from 430 degrees C to -170 degrees C.

30. Venus
Venus’s density and internal structure are similar to Earth’s, but they are still quite different.
The atmosphere is mostly carbon dioxide with clouds of sulfuric acid.
Atmospheric pressure is 90 times greater than Earth’s.
Its average surface temperature is 460° C, hot enough to melt lead.

31. Venus
This figure combines images of Venus taken from space with a camera (left) and radar (right). The camera image shows Venus’s thick atmosphere. Radar is able to penetrate Venus’s clouds to reveal the surface. Both images use false color.

32. Mars—The Red Planet
Mars is red because of the iron-rich dust that covers its surface. The thin atmosphere of Mars is more than 95% carbon dioxide. It’s surface temperatures range from -140°C to 20°C. It’s surface is rugged and rocky, with evidence of ancient volcanoes and lava flows. Mars has two tiny moons, Phobos (27km) and Deimos (15km). It’s tilted axis means it must have what phenomenon?
Mars
Seasons

33. Mars—Is there water?
Mars has ice caps at both poles. The ice is made up of water and carbon dioxide (dry ice).
Surface features that look like ancient streambeds and river canyons make scientists think that a large amount of liquid water once flowed on Mars's surface.
There may even be a large amount of water frozen underground.

34. Section 4: The Outer Planets
What characteristics do the gas giants have in common?
What characteristics distinguish each of the outer planets?

35. Gas Giants and Pluto
The four outer planets–Jupiter, Saturn, Uranus, and Neptune–are much larger and more massive than Earth, and they do not have solid surfaces. Pluto is small and rocky.

36. Jupiter’s Structure
Jupiter is composed mainly of the elements hydrogen and helium.

37. Jupiter
Has a core of rock and iron surrounded by liquid hyrdogen and helium. It has four large moons but dozens of smaller ones.
The Giant Red Spot on Jupiter is huge storm that is larger than Earth!
It is the largest and most massive planet in our solar system.

38. Saturn
Saturn has the most spectacular rings of any planet. It has a very thick atmosphere made of hydrogen and helium with visible clouds and even storms.
Rings: made of small particles of ice and dust.

39. Uranus
Although the gas giant Uranus is about four times the diameter of Earth, it is still much smaller than Jupiter and Saturn. It is very cold with clouds likely made of methane.
It has at least 27 moons.

40. Uranus
Uranus’s axis of rotation is tilted at an angle of about 90 degrees from the vertical.

41. Neptune
Neptune is a cold, blue planet. Its atmosphere contains visible clouds. It is very cold and often stormy.
It was discovered because it was predicted by a mathematical calculation. It was affecting the orbital pattern of Uranus.

42. Pluto
Pluto has a solid surface and is much smaller and denser than any of the outer planets. It is now considered to be a dwarf planet (or exoplanet).

43. Section 5: Comets, Asteroids, and Meteors
What are the characteristics of comets?
Where are most asteroids found?
What are meteoroids and how do they form?

44. Comets
A comet is a loose collection of ice, dust and small rocky particles orbiting around the sun. The most famous comet is probably Halley’s Comet, named after astronomer, Edmond Halley.

45. Structure of a Comet
The main parts of a comet are the nucleus, the coma, and the tail. The nucleus is deep within the coma. Most comets have two tails—a bluish gas tail and a white dust tail.

46. Comet Orbits
Most comets revolve around the sun in very long, narrow elliptical orbits.
Gas and dust tails form as the comet approaches the sun. The gas tail always points away from the sun due to the solar wind.

47. Origin of Comets
Most comets originate from one of two places: --The Kuiper Belt: a doughnut-shaped region of small icy bodies on the outer edges of Neptune’s orbit --The Oort Cloud: a large, spherical region of comets that surrounds the solar system

48. The Asteroid Belt
Most asteroids revolve around the sun in fairly circular orbits between the orbits of Mars and Jupiter.
This region of the solar system is called the asteroid belt.

49. Meteors
A meteoroid is a chunk of rock or dust in space. They are created when comets or asteroids collide or break up. When meteoroid enter Earth’s atmosphere, friction with the atmosphere creates a streak of light in the sky—a meteor (also known as a shooting star). If is it large enough, the meteoroid may not disintegrate and will strike Earth’s surface as a meteorite. Meteorites created the craters on the moon and likely wiped out the dinosaurs 65 mya.

50. Section 6: Is There Life Beyond Earth?
What conditions do living things need to exist on Earth?
Why do scientists think Mars and Europa are good places to look for signs of life?

51. Life On Earth
Earth has liquid water and a suitable temperature range and atmosphere for living things to survive. This is called the “Goldilocks” conditions (“just right”). Thought most organisms need these things to live, some extremophiles (organisms in extreme conditions) have been found to survive in a wide range of conditions (boiling water, frozen in ice, deep in the ocean, etc.)

52. Life on Mars?
Since life as we know it requires water, scientists hypothesize that Mars may have once had the conditions needed for life to exist.

53. Life on Europa?
Many scientists think the one of Jupiter’s moons, Europa, may have conditions necessary for life. They hypothesize that there might be liquid water under its smooth, icy crust.

54. Searching for Life in Space