1. Grade 9 Science: Unit 4
Chapter 11 Class Notes

2. The Sun We depend on the sun for many reasons: The food we eat
Our eyesight (light from the sun)
Gasoline in cars from fossilized plants that grew with energy from the sun.

3. The Sun Average sized star 300 000 times more mass than Earth
Approximately 5 billion years old, and has enough hydrogen to burn for another 5 billion!
It would take 110 Earths lined up side-by side to match the sun’s diameter.
99% of all mass in the solar system.
No solid surface

4. The Sun
Strong gravitational forces pull the Sun’s huge mass towards the centre of the sun.
This pressure and heat triggers Thermonuclear Reactions in which two or more atoms fuse (combine) to make a larger atom:
H (hydrogen)  He (helium) giving off Heat, Light and UV radiation in the process

5. The Sun
There is a “tug of war” going on inside any star, including our sun! The force of all the material trying to collapse the star is equally balanced by solar radiation moving out from the core of the star.
These forces are balanced and the star continues to shine for as long as its hydrogen fuel lasts.

6. The Sun
The Earth is located in the “Goldilocks Zone”, not too hot, not too cold, just right!
It is just the right distance away from the sun that it has allowed life to flourish!

7. The Sun At first, scientists used telescopes to observe the sun.
Today, technology has enabled scientists to monitor the sun from observatories in space!

8. The Sun
SUNSPOTS – dark patches of slightly cooler (3500°C) surface areas on the sun, they increase and decrease in number on an 11-yr cycle. They may be related to changes in the Earth’s climate .
SOLAR FLARES – eruptions of gas on the suns surface – can last a few hours, temperatures increase up to 11,000,000°C Creates Solar Winds

9. SOLAR WIND (page 393) Hot E bubbles “pop” on the surface of the sun and send high E particles rushing past Earth. Earth is protected from this solar wind by its magnetic field.
Some of the particles enter the Earth’s atmosphere at the poles where they collide with the gas in the atmosphere to create Auroras (Northern/Southern lights).

10. Northern/Southern Lights - Auroras

11. Northern Lights-Labrador

12. Luckily, Earth’s magnetic field deflects much of the solar wind around the planet.
However, some solar winds can disturb Earth’s magnetic field and disable satellites, knock out power lines, and expose astronauts to high levels of radiation!
Astronauts receive much more radiation in space then they do on Earth!

13. PHOTOSPHERE-the part of the sun most familiar to us!
Hot gas rises to the surface, cools, and then sinks back into deeper layers creating convection cells (gives sun a blotchy look).
Reaches 5800 °C

14. CORONA-the outermost part of the suns atmosphere.
A layer of gas that can reach °C

15. Labelling the Sun

16. New Technology More powerful telescopes were developed
Humans visited the moon
Uncrewed robotic space probes were sent to all the planets.
Probes used Radio communication return high quality pictures, much better than anything taken on Earth!
Robotic landers-landed on Venus and Mars and returned pictures of its surface!
Curiosity had landed, August 2012
“Water on Mars”
Curiosity “3 years on Mars”

17. Space Probe

18. Planets To be a planet you must… … orbit 1 or more stars
… be large enough so its gravity holds it in place
… be the only body in its orbital path

19. Planets are so far apart that kilometres are not a meaningful way of measuring distance, because the result is a huge number.
For this reason, astronomers use another unit of measure: the Astronomical Unit (AU), and it is equal to the average distance between the Sun and Earth, about 150 million km.
Earth is 1 AU from the Sun

20. Planet Profiles : Mercury
Closest and smallest planet to the sun
Extreme differences in night and day temperatures (400C during the day to -183C in the night)
Extreme heating and cooling causes Mercury to expand and contract, creating cracks in the surface.

21. Venus Earth’s sister planet (similar size and make-up of Earth)
Venus’ atmosphere is made up of carbon dioxide.
Large portions of Venus is flat. Other portions have volcanoes, lava flows, and cracks called rifts.

22. Earth
The only planet known to have water in 3 phases (liquid, solid, gas)
Water is ¾ of the Earth
Atmosphere is made up mostly of nitrogen and oxygen (essential to life)

23. Mars The Red Planet due to iron on its surface rocks.
Has a volcano that is 3x the size of Mount Everest and an 8 km deep Canyon that would stretch from Vancouver to Toronto!
Winds over 900km/h and dust storms that cover the planet

24. Jupiter Largest planet in our solar system
Its “great red spot” is visible from Earth
The spot is as large as 3 Earths, and is a raging storm of Hydrogen and Helium
Shortest day (turns once on its axis every 10 hours)

25. Saturn
Rings formed from ice particles (ranging in size from specks of dust to the size of houses)

26. Uranus Blue color from methane gas
Unusual rotation-flipped on its side
Rings made of ice and dust

27. Neptune
Outermost planet
Faint ring system

28. Moons All of the planets have moons except Mercury and Venus.
also called satellites
165 moons have been detected.
Earth’s Moon most likely formed early in Earth’s life. A body the size of Mars likely collided with Earth, sending debris into space in orbit around what was left of Earth.
Gravitational forces brought much of the debris back together to form Earth while other debris formed the Moon

29. Dwarf Planet
A dwarf planet is a celestial body orbiting the Sun that is generally smaller than a planet but massive enough for its own gravity to give it a round shape
Dwarf planets do not have enough mass or gravity, to clear their orbits of small debris left over from the formation of the solar system.
Pluto is the most famous, but Eris is the largest!
Others: Haumea, Makemake, Ceres

30. Asteroids
Asteroids are small bodies that are believed to be leftover remains of the formation of the solar system.
Most asteroids orbit the Sun in a band between Mars and Jupiter (Asteroid Belt)
The orbits of Near Earth Asteroids (NEAs) sometimes cross the orbit of Earth. The impact of an asteroid of 1 km in diameter on Earth would cause devastation

31. Trans-Neptunian Objects
Objects that circle the Sun beyond the orbit of Neptune are called trans-Neptunian objects.
The Kuiper Belt is a flat disk of millions of small bodies orbiting the Sun. It is thought to be composed of fragments of material left over from the formation of the solar system
A spherical cloud of small icy fragments of debris called the Oort Cloud is thought to be a source of comets. It is between and AU away from the Sun. (Earth is 1AU from the sun)!!!

32. Comets
Comets are often referred to as “dirty snowballs,” composed of ice, rock, and gas.
They hurtle through space, originating from the Kuiper Belt and the Oort Cloud.
Every once in a while they are bumped into the inner solar system.
They travel in a long, elliptical orbit around the Sun
Has a long dust tail that is a result of melting as it nears sunlight, leaving a streak of dust and gas.

33. Halley’s Comet
Halley’s Comet is the most famous comet because it is bright enough to see with the naked eye and appears more frequently than other comets (every 76 years).
The next time will be 2061

34. Meteoroids pieces of rock floating through space. They can be:
1. chunks of asteroids or planets broken by collisions with other asteroids or other bodies, or
2. they may even be debris left over from the formation of the solar system.
What some people call “shooting stars” are really meteors, which are meteoroids that burn up as they enter Earth’s atmosphere at high speed

35. Very occasionally, meteors are large enough to survive passing through the atmosphere, and they reach Earth’s surface. These chunks of rock are called meteorites
About once every 100 million years or so, extremely large meteorites strike Earth.

36. Meteor Terminology
Meteoroid – a rocky chunk, broken off an asteroid or planet, which floats through space
Meteor – a meteoroid that burns up as it passes through Earths atmosphere, seen as a shooting star
Meteorite – a meteoroid that does not burn up fully in the Earths atmosphere and hits the Earths surface