Unit 4: Astronomy

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)

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

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

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

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?

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

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.

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

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

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.

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

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

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

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