unit astronomy
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Astronomy
The Solar System
The Solar System is a collection of
A star
Planets
Satellites
Asteroids
Comets
Grouping
1. Inferior planets vs. Superior planets
I: Closer to the Sun than the Earth –
S: The distance from the Sun is greater
2. Terrestrial planets vs. Giant Planets
T: Small, rocky ones
G: Made of gas and very large
Pluto: odd one out, the former satellite of Neptune
The Planets travel round the central star
(=the SUN)
Signs
Terrestrial planets
Giant planets
Satellites:
Smaller rock bodies
All the planets have satellites (at least one each)
with the exception of Mercury and Venus
Earth: 1, Mars: 2
Jupiter: 16, Saturn: 23, Uranus:15, Neptune:8
Asteroids
Is a body orbiting the Sun which is
smaller than a planet.
1000s
The range in size between 1000km
across – 100-200 m across
The so-called ASTEROID BELT: most of
them are between the orbits of Mars and
Jupiter
Asteroids
Comets
Are bodies of gas, dust and rock which move on a long,
elliptical orbit around the Sun
They become very spectacular:
1. When they are close to the Sun
2. they warm up
3. gas and dust escape
4. they form a tail
5. the gases become ionised – give off light of their own
Comets
The Universe
The UNIVERSE – finite or infinite?
In the structure of expansion, this state began with the BIG
BANG
= A huge explosion which set the material of the Universe
in motion
1. The Solar System is situated in the
2. Milky Way - spiral galaxy – contains roughly 200 billion
stars
3. In the Local Group
4. In the Universe
The Milky Way
(side view, from above)
The structure of the Milky Way
The Universe - Exercises
1. Where is our Solar System located?
2. How far is the Sun from the centre of our galaxy?
Finish the sentences:
1. The Sun orbits once around the Milky Way in ……
2. Its velocity is ……
3. The Milky Way galaxy is moving ………
Flat? Geocentric? Heliocentric?
Ptolemy – Geocentric model
The Earth was the centre of the world and all the
planets went around it.
It was widely accepted until
the 17th century (!)
Copernicus – Heliocentric model (1543)
The centre of Universe was the Sun, and all the planets
orbited around it – the Earth as well as any other
Was not widely accepted
Became the accepted system
only after the work of Galilei and Kepler
Home assignment
The theories of Galilei and Kepler
