The Earth and Beyond

There are nine planets in our solar system: Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

We see planets and the moon because they reflect sunlight: The sun is different – it produces its own light.

The Earth orbits the sun every… …year (365 1/4 days)

This orbit is actually a “slightly squashed” circle (ellipse)

The Earth is kept in orbit by the force of… Gravity …and by the fact that is is moving at a high velocity

Gravity also keeps the moon in orbit around the Earth Gravity also keeps the moon in orbit around the Earth. The moon orbits the Earth every… …month (28 days)

Gravity is ________ if the planet has more mass: Jupiter Earth

How much of the moon we see depends on where the moon is in its orbit: Appearance:

Appearance:

Appearance:

The Earth is divided up into the northern hemisphere and the southern hemisphere: Equator

The Earth is tilted on an axis North pole South pole

The Earth spins on its axis every ___ (__ hours)

While the Earth is spinning the side that faces the sun is in ________

Because of this spin the sun rises in the ______ and sets in the ______

The tilt of the Earth on its axis is also responsible for the seasons: What date is it here? What date is it here? June 21st December 21st

The sun appears lower in the _______ than it does in the ______: Summer Winter Longer shadows in winter

Two things happen because of this tilt: The days are longer during the summer The weather is warmer during the summer (due to the hemisphere being closer to the Sun)

Comets Comets are balls of dust and frozen gas. They have very elliptical orbits: As the comet approaches the sun gases evaporate from it, forming a “tail”. This tail always faces AWAY from the sun

Solar systems, galaxies and the Universe (Basically, everything in the universe orbits around something else) OUR SUN is one of millions of stars that orbit the centre of… THE MILKY WAY, which is one of a billion galaxies that orbit AND move away from the centre of… THE UNIVERSE

Quiz.. What is the sixth planet in the solar system? What is the biggest planet in the solar system? Name 2 differences between stars and planets How long does the Earth take to orbit the sun? What force keeps the Earth from flying away from the sun? Where does this force point towards when it acts on the Earth? How long does the moon take to orbit the Earth? Would the acceleration due to gravity on Mars be bigger or smaller than on the Earth? Which hemisphere is Britain in?

Quiz.. What is the name of the line that divides the two hemispheres? How long does the Earth take to rotate? Where does the sun rise and set? What does the tilt of the Earth’s axis cause? What is the date when the northern hemisphere is tilted towards the sun as far as possible? How would you describe the shape of a comet’s orbit? What is a comet made up of? What point do different galaxies orbit around and move away from? What keeps these galaxies in their orbits?

Evidence about the origins of the universe…

Source of light “Spectra”

If you pass the light through a gas something different is seen… helium Some wavelengths of light are absorbed by the gas.

These patterns are called absorption spectra… …because they show which wavelengths of light are absorbed by the gas (this is how we know the sun is made of helium).

If the light starts to move away…

Before helium After The results look a little different…

The absorption lines have all been “shifted” towards the longer wavelength end (red end)… This is called red shift. The faster the light source moves the further its light will be “shifted”

This is the BIG BANG theory Light from different stars and from the edge of the universe also shows this “red-shift”. This suggests that everything in the universe is moving away from a single point. This is the BIG BANG theory

Red shift summary White light is made up of the colours of the visible _______. Each colour has a different __________. When this light is passed through a gas certain wavelengths are _________ - the patterns produced are called _________ ________: If the light source is moving ___ from us we would find that the absorption lines are all _______ towards the ___ end of the spectrum (the longer wavelength end). The ________ the light source is moving the further its pattern is shifted. Light from the edge of the ______ also shows this pattern, so we assume that the edges of the universe are all moving away from a single point. This is called the ___ _____ theory. Words to use – shifted, red, spectrum, Big Bang, absorbed, wavelength, absorption spectra, away, universe, faster

The Life Cycle of a Star

Stage 1: NEBULAE A nebulae is a collection of dust, gas and rock. Some examples of nebulae… A NEBULA is a collection of gas, dust and ice.

(No need to know these names) Dark nebula

(No need to know these names) Emission nebula

(No need to know these names) Planetary nebula

(No need to know these names) Reflection nebula

Stage 2: PROTOSTAR Gravity will slowly pull these particles together… The force of gravity makes the dust particles come spiralling in together. As they do so their gravitational potential energy is converted into heat energy and the temperature rises… As they move inwards their gravitational potential energy is converted into heat and a PROTOSTAR is formed

Stage 3: MAIN SEQUENCE STAR In a main sequence star the forces of attraction pulling the particles inwards are BALANCED by forces acting outwards due to the huge temperatures inside the star. Stars are basically nuclear reactors that use hydrogen as a fuel. During its main sequence a star will release energy by converting hydrogen and helium (light elements) into heavier elements. Eventually the temperature rises enough for the hydrogen gas to undergo nuclear fusion. A massive amount of heat and light are given out and the star is stable for around 10,000 million years. Our sun is an example of a main sequence star – it’s in the middle of a 10 billion year life span

Stage 4: RED GIANT Eventually the hydrogen and helium will run out. When this happens the star will become colder and redder and start to swell, forming a RED GIANT. Eventually the hydrogen begins to run out and the star swells into a red giant. (At this point our sun will suck in Earth and the planets around it)

Stage 5: THE DEATH What happens at this point depends on the size of the star… 1) For SMALL stars the red giant will collapse under its own gravity and form a very dense white dwarf: Red giant For small stars the star will shrink into a WHITE DWARF and then it cools and fades to a BLACK DWARF (like a dying fire) White dwarf Black dwarf

This explosion is called a SUPERNOVA 2) If the red giant is VERY BIG it will shrink and then EXPLODE, releasing massive amounts of energy, dust and gas. When a big star runs out of fuel it would collapse and blow off its outer layer in an enormous explosion called a SUPERNOVA (click to show picture) Before After This explosion is called a SUPERNOVA

If the star is big enough it could become a BLACK HOLE. The dust and gas on the outside of the supernova are thrown away by the explosion and the remaining core turns into a NEUTRON STAR. If the star is big enough it could become a BLACK HOLE. The dust and gas on the outside of the supernova are thrown away by the explosion and the remaining core turns into a NEUTRON STAR. If the star is big enough it will become a BLACK HOLE. (The picture shows a black hole after forming in the middle of other stars)

Stage 6: Second generation stars The dust and gas thrown out by a supernova can be used to form a new star… Our sun is believed to be a “second generation star” – this is because it contains some heavier elements along with hydrogen and helium. These heavier elements would have been the products of a previous star that have been thrown out by a supernova. These heavier elements are also found on planets, indicating that they might have been made from remains of previous stars as well. The dust and gas thrown off by the supernova will form SECOND GENERATION stars (like our sun) and a new solar system