1. Stars, Constellations and Planets
4th Grade Science
Earth Science
Unit IV: Stars and Solar Systems
S4E1 & S4E2

2. stars

3. Activating video
m%20A%20Star%20The%20Stars%20Song%20by%20StoryBots.avi I’m Star video

4. If you went outside on a clear evening and brought along a blanket and were to lie down and look in the sky what would you see?

5. What is a star?
A star is a massive, bright, sphere of very hot gas called plasma which is held together by its own gravity.
Stars radiate energy created from nuclear fusion, which is a process that takes place in a star's core and involves hydrogen fusing (burning) to make helium.

6. How do stars form?
Stars form when enough dust and gas clump together because of gravitational forces. Nuclear reactions release energy to keep the star hot. Planets form when smaller amounts of dust and gas clump together because of gravitational forces.
Stable stars like the Sun change during their lifetime to form other types of stars, such as red giants, white dwarfs, neutron stars and black holes. The fate of a star depends upon how much matter it contains.

7. Star facts
The nearest star to Earth is the Sun, which is classified as a G2 yellow dwarf star.
There are approximately billion stars in our Milky Way Galaxy alone.
Each galaxy contains hundreds of billions of stars and there is estimated to be over 100 billion galaxies in the universe. So the total number of stars in the universe is mind boggling, estimated to be at least 70 sextillion and possibly as high as 300 sextillion, that's 300,000,000,000,000,000,000,000!!!!!
Stars are usually between 1 and 10 billion years old. Some stars may even be close to the age of the observed Universe at nearly billion years old.

8. What might you see in the night sky?

11. Astronomers classify stars according to their physical characteristics
Astronomers classify stars according to their physical characteristics. Characteristics used to classify stars include color, temperature, size, composition, and brightness.
What does composition mean?

12. One way scientists classify stars is by color
One way scientists classify stars is by color. Star colors range from blue, white, and yellow to orange and red. The color of a star is a clue to its surface temperature. Blue stars are the hottest, and red stars are the coolest. Our sun is between the hottest and the coolest stars.

13. The brightness of a star depends upon both its size and its temperature. How bright a star looks from Earth depends on both its distance from Earth and how bright the star actually is.
Distances on Earth’s surface are often measured in kilometers. However, distances to the stars are so large that kilometers are not very practical units. Astronomers use a unit called the light-year to measure distances between the stars.
A light-year is the distance that light travels in one year, about 9.5 million million kilometers.

14. The two most important characteristics of stars are temperature and absolute brightness.

15. Stars Grouped by Size
Supergiants are the largest stars, and may have diameters several hundred times the size of the Sun.
Giants are more common than Supergiants, and have diameters 10 to 100 times as large as the Sun. Red Giants have cooler temperatures than giants, and are thus less bright, but their size is still massive.
Medium-size or dwarf stars are about as large as the sun.
White dwarfs are small stars (smaller than the distance across Asia).

16. The Sun is a star!!!!
What do you see?

17. Constellations

18. History of Constellations
When ancient observers around the world looked up at the night sky, they imagined that groups of stars formed pictures of people or animals. Today, we call these imaginary patterns of stars constellations

19. When we talk about constellations, do you know what they are?  

20. The first thing you need to know is that constellations are not real!
The constellations are totally imaginary things that poets, farmers and astronomers have made up over the past 6,000 years (and probably even more!). The real purpose for the constellations is to help us tell which stars are which, nothing more. On a really dark night, you can see about 1000 to stars. Trying to tell which is which is hard. The constellations help by breaking up the sky into more managable bits. They are used as mnemonics, or memory aids.

21. What do you see?

22. Examples of constellations

24. Constellations vs. galaxies vs universe
These stars form a constellation, a group of stars that form an imaginary picture in the sky.
A galaxy is a huge system of gases, dust, and stars.
Galaxies contain billions of stars. 
The universe is everything that exists in space.

25. Compare stars to planets
What are some comparisons of planets and stars just by looking at this picture?

26. Video link
mparison%20of%20planets%20and%20stars.mov

27. Planets

28. A solar system is a group of objects in space that orbit a star in the center, plus the star itself. The sun is the star in the center of our solar system. Everything else in the solar system is small compared to the sun.
Our solar system contains a variety of objects. These include planets, “dwarf planA planet is a large object that revolves around a star in a clear orbit. ets,” moons, and asteroids. A “dwarf planet” also revolves around a star, but its path is not clear of other objects. A moon is a smaller object that revolves around a planet.

29. The Inner Planets
The inner planets are those closest to the sun. They are Mercury, Venus, Earth, and Mars. These planets are alike in many ways. They all have rocky surfaces and are smaller than most of the outer planets. 

30. The Outer Planets
Beyond Mars, on the far side of the asteroid belt, are the outer planets. They are Jupiter, Saturn, Uranus, and Neptune.
These four planets are huge and made mostly of gases. They have no known solid surface. Their atmospheres blend smoothly into the denser layers of their interiors, very deep beneath the outer layers. For this reason, these planets are often called the gas giants. 

31. In our solar system, there are eight planets
In our solar system, there are eight planets. Often, scientists group them as the inner planets and the outer planets.

32. The Earth and its Motion

33. What is the difference between rotating and revolving?
Think Question
What is the difference between rotating and revolving?

34. The changes of the seasons, as well as the changes of night and day, occur because of the ways Earth moves.
Earth moves in two ways. You have learned that Earth rotates on its axis. It takes about 24 hours for Earth to make one complete rotation.
In addition to rotating on its axis, Earth revolves, or travels in a path around the sun. An object’s path in space around another object is its orbit. Earth’s orbit takes about 365 days, or one year.

36. You may know that Earth is divided into Northern and Southern Hemispheres by the equator. The equator is an imaginary line going all the way around Earth halfway between the North and South Poles.

37. Think Question
Do we have summer because the Earth is closer to the Sun during the summer?

38. It’s the tilt of Earth’s axis that produces seasons.
As Earth revolves, one part is tilted toward the sun. That part of Earth takes in more energy from the sun in the form of heat. The part that is tilted away from the sun takes in less energy from the sun.

40. Moon Phases

41. The moon is a small planetlike body that revolves around Earth rather than the sun. As Earth revolves around the sun, the moon revolves around Earth.
The moon appears to shine, but the light you see is actually reflected light from the sun. As the moon revolves around Earth, different amounts of its lit surface can be seen. That’s why the moon seems to have different shapes, or phases.

42. Phases of the moon

43. During the first half of the moon’s cycle, the amount of the lit side of the moon seen from Earth waxes, or increases.
During the second half of the moon’s cycle, the amount of the lit side of the moon seen from Earth wanes, or decreases. Then the cycle begins again.