ASTROPHYSICS: That branch of astronomy which treats of the physical or chemical properties of the celestial bodies. Hence astrophysicist, a student of astronomical physics. ASTRONOMY: The science which treats of the constitution, relative positions, and motions of the heavenly bodies; that is, of all the bodies in the material universe outside of the earth, as well as of the earth itself in its relations to them.
Our Universe What it is like, how it started, how it evolved to its current state, and how it will end Today we will talk about:
First, lets look at some of the objects we might find if we explored our Universe
Stellar Facts A star is a big ball of burning gas Our Sun is a very average star When we look out into the night sky, many of the stars we see are very similar to our own sun In fact some of these stars also have planets, just like our own Solar System
We live on the Earth The Earth is a planet in the Solar System, orbiting our star which we call the Sun The Sun is part of a galaxy When we look out into the sky at night, all of the stars we see are in our galaxy But our galaxy is just one of many…..
The Big Bang Not really an explosion Universe expanded rapidly as a whole (Universe is still expanding today as a result of the Big Bang) Matter was created in the form of tiny particles (protons, neutrons, electrons) Too hot for normal stuff to form (eg atoms, molecules)
Gravitational Collapse We started with a uniform gas Small regions became more dense The denser regions had larger gravity and started to pull other particles towards them The gaseous Universe began to look clumpy
Future? The Universe is still expanding All galaxies are moving apart The explosion of the big bang is still happening! It may contine expanding forever Or is may stop expanding, and fall inwards in a big CRUNCH!
What have we learnt? The Universe started with a BIG BANG Gradually the particles were drawn together under GRAVITY to form STARS and GALAXIES Many stars have planets around them The fate of the Universe is uncertain…