1. Unit 4: Astronomy

2. Astronomy The scientific study of what is beyond Earth
NOT to be confused with Astrology (The study of the movements of celestial objects as having an influence on human affairs)

3. Celestial Object Any object that exists in space. Examples Stars
Planets
Asteroids Celestial objects can be enormous!
Comets
Galaxies
Star systems
satellites

4. Universe
Everything that exists, including all energy, matter and space.

5. Star
A massive collection of gases, held together by its own gravity and emitting large amounts of energy.
Examples
The Sun
Polaris
Sirius
Betelgeuse
VY Canis Majoris

7. Luminous Producing or giving of light; Shining.
Examples of luminous celestial objects:
Stars
Star systems
Galaxies
If only stars are luminous, then how do we see other non-luminous celestial objects?

9. Planet A large, round celestial object that travels around a star.
Example:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Try to develop a mneumonic device that can help you remember the order of planets
Examples: My Very Elderly Mother Just Served Us Nachoes

10. Planet To be classified as a planet, a celestial object must:
Orbit a star and no other celestial object
Contain enough mass so that its gravity pulls it into a round or spherical shape, and
Be able to clear other celestial objects around it.

11. Planet
A planet may be classified as terrestrial (Earth-like and rocky) or as a gas giant (made primarily of gases, usually of low density)
Terrestrial Planets
Gas Giants
Mercury
Jupiter
Venus
Saturn
Earth
Uranus
Mars
Neptune

13. What makes Earth special?
Existence of liquid water in large amounts
High biodiversity (compared to other planets)
Plate tectonics
Highly active and heterogeneous atmosphere

14. Solar System The Sun and all the objects that travel around it.
Not necessarily all the objects under the influence of the Sun’s gravity.

15. Satellite
A celestial object that travels around a planet or a dwarf planet.
Example
The Moon around the Earth
Phobos around Mars
Europa around Jupiter

16. Orbit
The closed path of a celestial object or satellite as it travels around another celestial object.
Example:
Earth takes ~365 days to travel a full orbit around the Sun
Neptune takes ~165.8 Earth years to complete one full orbit around the Sun

18. Galaxy
A huge, rotating collection of gas, dust and billions of stars, planets, and other celestial objects.
Examples:
The Milky Way (our galaxy)
The Andromeda Galaxy

20. Homework Read section 8.1 and answer the following questions:
How much more massive and how much more voluminous is the Sun compared to Earth?
What is scientific notation? Provide an example and explain why using this notation is useful when studying astronomy.
How far is the next closest star to us after the Sun?
Which 5 planets can be seen with the unaided eye?
Put the following terms in order from smallest to largest: North America, Canada, Earth, Mississauga, Ontario, The Milky Way Galaxy, The Solar System, The Universe, John Fraser Secondary School
Answer questions 1-8 on page 308