Introduction to Astronomy SNC1P Findlay

Learning Goals Students will: Learn about the objects visible in the night sky. Learn how to locate objects in the night sky. Learn about distances used for the larger scales of the universe.

What do we see when we look at the night sky?

We see stars that we organize into patterns. The sky is shaped like an upside-down bowl with the rim of the bowl being the horizon. This model is called the celestial sphere.

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

We see stars that we organize into patterns. The stars in the sky appear to move from east to west. In the northern hemisphere, they seem to rotate around a fixed point in the sky, which is the north star (Polaris). Why do the stars appear to move from east to west?

Navigating the night sky with Polaris Polaris is useful because it can help people in the northern hemisphere find north at night. Polaris is the last star in the handle of a constellation called Ursa Minor (Little Bear) or the Little Dipper. A constellation is a shape or pattern of stars in the night sky made by imagining that stars are joined together by make-believe lines.

Navigating the night sky with Polaris The constellations that travel around the pole star (Polaris) are called the circumpolar constellations. The circumpolar constellations are visible all year long in Canada. Which of these constellations have you seen before?

Locating Stars in the Night Sky

Star Clusters A group of stars in our galaxy that all orbit each other Open cluster – a few stars to a few thousand stars – no distinct shape Globular cluster – A few thousand stars up to a million stars – spherical shape

We see celestial objects in 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.

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.

Birthplace of Stars A nebula is a large cloud of gas and dust in our galaxy. Horsehead Nebula Crab nebula Eagle nebula

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.

The Milky Way Contains over 200 billion stars!

Andromeda Galaxy Our neighbour contains twice as many stars as the milky way.

Galaxies come in many different sizes and shapes. Classifying Galaxies Galaxies come in many different sizes and shapes. How could you classify galaxies based on their similarities and differences?

Clusters of Galaxies Largest structures in the universe.

Moon Watching Assignment

We see objects separated by immense distances 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.

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).