Lesson 1

Introduction to the Universe

IB Physics Power Points

Option E

Astrophysics

www.pedagogics.ca

E.1.1 Outline the general structure of the solar system

8 planets orbiting the Sun

Orbital path around the Sun is not circular.

E.1.2 Distinguish between a stellar cluster and a constellationStar clusters or star clouds are groups of stars. A globular cluster is a tight group of hundreds of thousands of very old stars which are gravitationally bound. Stars in a cluster are relatively close to each other.

Omega Centauri is the most massive globular cluster in our Galaxy

E.1.2 Distinguish between a stellar cluster and a constellationConstellations are patterns formed by prominent stars in the night sky. Although they appear close to each other, stars in constellations can vary greatly in their distance from Earth.

Cassiopeia

E.1.3 Define the light year

A unit of distance equivalent to how far light travels through space in one year

Our Sun is part of a large collection of stars called a galaxy (ours is called the Milky Way and consists of over 100 billion stars). Get used to vast distances!

E.1.4 Compare the relative distances between the stars within a galaxy and between galaxies in terms of order of magnitude.

Nearest star to our Sun – Proxima Centauri 4.2 ly away. There are only 8 stars within 101 ly

Diameter of Milky Way galaxy is 105 ly

Andromeda is our nearest neighbor galaxy – about 2.9 x 106 ly from the Milky Way

E.1.5 Describe the apparent motion of the stars/constellations over a period of a night and over a period of a year, and explain these observations in terms of the rotation and the revolution of the Earth.

Diurnal motion - the apparent circular motion of stars around the Earth. This observation occurs because the Earth is rotating.

The apparent westward motion of constellation in the night sky over a period of a year is due to the revolution of the Earth around the Sun.