1. Unit 5: The Universe & Gravity
8th Grade

2. Electromagnetic Waves
What is a vacuum?
EM wave
This energy is called EM radiation
A place that is empty of all matter
Space is nearly a vacuum
Vibrating electric and magnetic fields
Can move through vacuum or matter
Move at the speed of light (300,000 km/s)
Sun’s energy arrives on Earth as EM radiation
Infrared, visible, and UV 62

3. Electromagnetic Spectrum
Radio waves
Microwaves
Infrared rays
Visible light
Radio signals, WiFi
Microwave ovens, cell phones, radar
“Heat rays”
Sun, heat lamps, thermogram
Smallest part of the EM spectrum
The only EM waves we can see
ROYGBIV 62

4. Electromagnetic Spectrum
Ultraviolet (UV) rays
X-rays
Gamma rays
Kills cells (sunburn, cancer)
Small amounts cause skin to make vitamin D
Can penetrate most matter
Bones/lead are dense and absorb x-rays
Examine internal organs
Very dangerous, but blocked from space by Earth’s atmosphere 62

5. Space Exploration How do we use radiation to explore space?
Telescopes, satellites, and laser devices all use parts of the EM spectrum to help us gather information about space 64

6. Space Exploration 64 Telescopes
Collect and focus forms of EM radiation coming from space
Optical telescopes – visible light
Radio telescopes – large, focus radio waves
Spitzer Space telescope – takes infrared pics of space
Chandra X-ray Observatory – in orbit, takes x-ray pics 64

7. Space Exploration 64 Satellites Hubble Space Telescope
Some take photographs of Earth’s surface
Made of pixels
Used for mapping
Some are used for global communication
In orbit, flies near planets to take pictures of them in different types of light 64

8. Scale of the Universe 66 Universe Astronomers
All of space and everything in it
Contains billions of galaxies, which contain billions of stars
Enormous beyond imagination
Scientists that study astronomical bodies in the universe and radiation
Study very large (galaxies) and very small (atoms) objects in space 66

9. Distance in Space 68 Scientific notation
How do I write a number in scientific notation?
Used to describe very large or very small numbers
Sizes or distances
Puts long numbers in a shorter form
Add a decimal to the number to make it between 1 and 10
Count how many numbers follow the decimal and make it a power of 10 68

10. Distance in Space Light-year The distance light travels in one year
9.5 trillion kilometers
Light is the fastest thing that exists
300,000 km/s 68

11. Astronomical Objects Nebula Galaxy
Large cloud of gas and dust particles
“Star nurseries” where new stars form
Huge group of single stars, solar systems, star clusters, gas, and dust
Held together by gravity 70

12. Astronomical Objects 70 Solar system Star Planet
Contains one star and all planets that revolve around it
Giant ball of gas
Nuclear fusion
Revolves around a star
Rounded by gravity
Some made of rock and metal, others made of liquids and gas 70

13. Astronomical Objects Moon Dwarf planet Orbits a planet AKA “satellite”
Small planet that is not gravitationally dominant 70

14. Gravity Orbit Why don’t planets orbiting the sun fly off into space?
The path of an object moving around another object in space
The force of gravity holds them in place
A force that attracts objects to each other 72

15. Gravity 72 Law of Universal Gravitation
What two factors control the strength of gravity?
Every object in the universe attracts every other object
Mass – amount of matter in an object
Distance – as distance increases, gravity decreases
Mass does not change, but weight can change depending on location 72

16. Gravity How do we measure the strength of gravity?
How does mass affect gravity?
Weight – measures the force of gravity on an object
Greater mass = greater gravitational pull = greater weight 72

17. Motion
If the sun pulls on Earth, why doesn’t Earth crash into the sun?
Why do objects stay in orbit?
Inertia – an object resisting a change in motion.
Greater mass = greater inertia = more difficult to start or stop
The force of gravity and inertia combined keeps objects in orbit 76

18. Formation of Planets, Stars, and Solar Systems
How do astronomical objects form?
Solar systems
Accretion – gravity brings materials together and slowly builds them up
Begin as clouds of hydrogen, helium, rock, ice
Gravity pulls the materials together
Cloud begins to rotate and forms a spinning disk 78

19. Formation of Planets, Stars, and Solar Systems
Material in spinning disk pulled toward center
Gasses tightly packed from accretion = greater temperature and pressure
Causes hydrogen atoms to fuse together to form helium (nuclear fusion) 78

20. Formation of Planets, Stars, and Solar Systems
What keeps solar systems together?
Other rock, ice, and gasses in the spinning disk begin to pull together
The gravity of the center star 78

21. Star Properties – Color, Temperature, and Size
How do stars produce electromagnetic energy?
How do astronomers classify stars?
Through the process of nuclear fusion
Using characteristics including color, temperature, size, composition, and brightness 82

22. Star Properties – Color, Temperature, and Size
How do scientists know the surface temperature of a star?
Using the color of the star
Red stars = coolest (3,200⁰C)
Yellow = medium (5,500⁰C)
Blue = hottest (over 20,000⁰C) 82

23. Star Properties – Color, Temperature, and Size
Size of stars
Giants or supergiants = very large stars, larger than our sun
White dwarfs = small, about the size of Earth
Neutron stars = very small, about 12.5 miles in diameter 82

24. Star Properties – Composition and Brightness
How do scientists know what stars are made of (composition)?
Using a spectrograph – breaks light into colors and produces an image of a spectrum
Each gas element in a star absorbs a specific wavelength of light
The wavelengths that were absorbed show up as thin lines on the spectrum
Lines create a unique pattern 84

25. Star Properties – Composition and Brightness
What are stars made of?
Which two factors do scientists use to determine the brightness of a star?
Most stars are about 73% hydrogen, 25% helium, and 2% other elements
Size and temperature
Apparent brightness = how bright a star appears from Earth
Absolute brightness = how bright stars would be if they were all the same distance from Earth
Apparent brightness + distance from Earth 84

26. The Sun 86 Does the sun have layers like the earth?
What features can you see on the sun?
Yes, but no solid surface
3 interior layers
3 atmospheric layers
Solar flares – powerful eruptions of gas from the sun into space
Solar prominences – huge loops of gas that connect two sunspot areas 86

27. The Sun What features can you see on the sun (cont.)?
Sunspots - dark areas “spots” on the sun’s surface
Caused by spots of gas that are cooler than the other gas around them
Cooler gas gives off less light, so the spots appear darker 86

28. The Sun How often do sunspots appear? Do sunspots move?
They appear in a cycle
Number of sunspots rises and falls every 11 years
Yes, we can track the movement of sunspots
Different sections of the sun rotate at different speeds 86