Transcript Slide 1

EARTH & SPACE
Celestial Objects
THE UNIVERSE
The universe includes everything that exists. This includes
celestial objects such as stars and planets, plus all the
matter and empty space surrounding them.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Our Solar System
The solar system is a system of planets, including Earth,
moons, and other objects, that orbit the Sun.
An orbit is the circular
(or elliptical) path of
one object around
another object.
The gravitational pull (a force of attraction between two
masses) between the Sun and the planets keeps the planets
revolving around the Sun.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Stars and Their Characteristics
A star is a massive ball of superheated gases that radiates
heat and light.
Characteristics
used to describe
stars include:
• size
• colour
• temperature
• and density
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Galaxies: Collections of Stars
A galaxy is a collection of billions of stars, plus gas and dust,
held together by gravity. There are billions of galaxies in
the universe.
Our solar system is located in a galaxy called the Milky Way.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Distances in Space
Distances in space are so large that well-known units such as
kilometres are almost meaningless.
To measure the immense distances in space, astronomers
have created a unit called the astronomical unit (AU).
1 AU is equal to
the distance
between Earth
and the Sun, which
is about
150,000,000 km.
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Distances Involving Galaxies
Distances involving galaxies are much larger than those
involving solar systems. Instead of using AUs, scientists use
a unit called a light-year, which is a measurement equal to
the distance that light travels in one year.
With light travelling at 300 000 km/s, one light-year is
equal to about 9 500 000 000 000 km (9.5 x 1012km).
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Classifying Galaxies
Galaxies come in many different sizes and shapes.
Bill Nye - Outer Space
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Topic 3.1 Review
Key Concepts to be reviewed:
• We see stars that we organize into patterns.
•We see celestial objects of the universe.
•We see objects separated by immense distances.
Copyright © 2010 McGraw-Hill Ryerson Ltd.