The Solar System and our Universe

Additional Information

The Solar System contains the following parts

• Star (Sun) • Planets• Dwarf planets• Natural satellites• Comets• Meteors• Asteroids• Moons

P9 – Describe the composition of the solar system.

Sun

• This is a star at the centre of the solar system.

• The heat & light from the sun is caused by nuclear reactions in its centre.

• It is one of may billions of stars which form the Milky Way galaxy.

• Gravity is the force that keeps the stars together in the galaxy.

Planets• They are large balls of

rock / gas that travel around the Sun in ellipses.

• There are 8 planets in the solar system

• They reflect sunlight

• Inner planets (closet to the sun) – Mercury, Venus, Earth & Mars.

• Outer planets (further away) – Jupiter, Saturn, Uranus, Neptune.

• Planets orbit around the stars.

• Pluto is not strictly a planet.

• They often have moons orbiting them. They are much smaller than their planets.

• Planets are held in orbits by the gravitational pull of the Sun.

Dwarf planets

• Orbit the Sun, smaller than planets.

• Less effect on their surroundings than planets.

• Pluto is a dwarf planet.

Natural satellites

Comets• Orbit the Sun in elongated elliptical orbits.

Taking them very far away & then back in close.

• Made of balls of ice & dust.• Orbit different planes from the planets.• When the comet approaches the sun , its ice

melts, leaving a bright tail of gas & debris.• The comet speeds up as its approaches the

sun. The pull of the Sun’s gravity is stronger the closer you are to the Sun.

Comets

• Travel through space

• When close, the comet appears to have a tail streaking out from behind it.

• May be left-overs from when the solar system was formed

Meteors

• They are also called – ‘Shooting Stars’.

• They occur when rocks burn up as they pass through the Earth’s atmosphere.

Asteroids

• Similar to planets & dwarf planets.• Much smaller• Found orbiting between Mars and Jupiter.

Orbit the Sun in the asteroid belt.• Fragments of rock, up to 1000km in

diameter.• Formed at the same time as the solar

system.

Moons

• Smaller than their planets, found close to the planet.

• Made up of smaller lumps of rock that travel around planets

• Some planets have several moons

Identify evidence that shows how the universe is changing.

P10

• Red Shift (galaxies moving away from each other)

• Cosmic background radiation,

• Star galaxies

Red Shift• This is the light from far-away galaxies, the

lines in the spectra were redder than expected.

• The red shift is bigger when a galaxy is further away from Earth.

• All galaxies were moving away from Earth, the most distant galaxies are moving faster.

• The universe is expanding!• More distant galaxies have greater red-shifts

than near ones.

Cosmic Background Radiation

• 40 years ago faint radiation was detached coming from all directions of space.

• This is called : Cosmic background radiation.

• Confirmed the theory that the universe began as a ‘big bang.’

Star Galaxies

• Telescopes (Hubble Space Telescope) take photos of stellar explosions & nebulae.

• Provided evidence that throughout the universe stars are dying, and new stars & galaxies are constantly forming.

Big Bang (M5)

• Everything from the universe originated from the same point & then exploded apart.

• Since the explosion the universe has been expanding & cooling.

• The big bang occurred – 11 – 18 billion years ago.

Big Bang (M5)

• This theory, suggests that all the matter & energy in the Universe must have compressed into a very small space.

• Then it exploded & started expanding.• The expansion is still occurring. • The current rare of expansion of the Universe to

estimate its age• The estimate might not be very accurate, it’s hard

to tell how much the expansion has slowed down.

Big Bang (M5)

• The rate of which the expansion is slowing down is an important factor in deciding the future of the Universe.

• Without gravity the Universe would expand the same rate forever.

• All the masses in the Universe attract each other & tend to slow the expansion down.

The ‘Steady State’ Theory (M5)

• This states that the universe has always existed as it is now, & it always will do.

• The Universe appears pretty much the same everywhere.

• It explains the apparent expansion by suggesting that matter is being created in the space as the Universe expands

How was the solar system formed? (M5)

• Stars form from swirling clouds of dust & gases in space – Nebulae.

• Gravity makes the centre of the cloud clump together.

• The clump is so massive that gravity crushes the particles very, very tightly.

• The centre heats up to million of degrees.• This is hot enough for nuclear fusion

reactions to ignite• The star starts to shine & gives out heat.

• As the star forms, the outer edges of the cloud are still swirling around the centre.

• The particles of dust & gas may clump together, attracting other particles.

• The gravity is not strong enough for nuclear reactions to ignite.

• Strong enough to hold the particles together.

• This is how planets are formed.

• Their movement means that the orbit the star, and the solar system is complete.

• The Universe is the whole of space & includes billons of groups of stars – Galaxies.

• Galaxies – each with billion of stars, many with a solar system.

• Our galaxy is called Milky Way.• In a stars lifetime, it changes size & colour as

different reactions take place in its core.• Some stars explode, flinging out elements that

have formed in the nuclear reactions in their core.• These particles form new Nebulae – Where new

stars will form.

What does the evidence tell us about the origin of the Universe?

(M5 & M6)

• Scientists believe that the red shift evidence tells us that at some point in time, billions of years ago, all the mater & energy in the Universe was concentrated in the same place.

• A massive explosion tool place – Big Bang.• It flung all the matter & energy apart• As the new Universe cooled, particles formed &

clumped together, making star & galaxies• The Universe has been expanding & cooling

down.

Is the theory right? (D5 & D6)

• The discoveries of the red shift of distant galaxies & the cosmic background radiation suggest that the Big Bang theory is right.

• There is no strong counter-evidence to say it is wrong.

• It cannot be proved, but most scientists believe the Big Bang took place.

• We will never know what happened before the Big Bang or what caused it.

• The evidence that the Universe is still changing is strong.

• Photos can record the changes clearly.• They can not tell us what is happening now, but

what happened in the past.• Light from stars takes years to reach us & we have

even detected light from stars formed soon after the Big Bang that has taken 14 billion years to reach us.

Is the theory right? (D5 & D6)

The Future of the Universe (D5 & D6)

• The fate of the Universe depends on how fast the galaxies are moving apart & how much total mass there is in it.

• There are 2 ways the Universe could go:

1. Big Crunch

2. Oblivion

Big Crunch• Mass everywhere is attracted together by gravity.• This could slow the Universe’s expansion.• If there is enough mass compared to how fast the

galaxies are currently moving, the Universe will eventually stop expanding & then begin to contract

• This would end in a BIG CRUNCH.• The Big Crunch could be followed by another Big

Bang & then endless cycles of expansion & contraction

• This is called the Oscillating Universe theory.

Oblivion

• Too little mass in the Universe to stop the expansion, it could expand forever with the Universe becoming more & more spread out into eternity.

What does the evidence tell u

How the universe is changing (D5 & D6)

• The universe will keep on expanding - The galaxies move fast enough to overcome the forces of gravity acting between them.

• The expansion will slow down & stop – The galaxies will remain in a fixed position, The gravitational forces will exactly balance the ‘expansion forces.

• The universe will start to contract – The force of gravity acting between the galaxies will overcome the forces causing expansion & pull them back together again.