The Solar System and our Universe

1. The Solar System and our Universe Additional Information

2. P9 – Describe the composition of the solar system. The Solar System contains the following parts • Star (Sun) • Planets • Dwarf planets • Natural satellites • Comets • Meteors • Asteroids • Moons

3. 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.

4. 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. Planets

5. Dwarf planets • Orbit the Sun, smaller than planets. • Less effect on their surroundings than planets. • Pluto is a dwarf planet.

6. Natural satellites

7. 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.

8. 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

9. Meteors • They are also called – ‘Shooting Stars’. • They occur when rocks burn up as they pass through the Earth’s atmosphere.

10. 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.

11. 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

12. Identify evidence that shows how the universe is changing. P10 • Red Shift (galaxies moving away from each other) • Cosmic background radiation, • Star galaxies

13. 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.

14. 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.’

15. 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.

16. 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.

17. 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.

18. 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.

19. 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

20. 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.

21. 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.

22. 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.

23. 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.

24. 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.

25. Is the theory right? (D5 & D6) • 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.

26. 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: • Big Crunch • Oblivion

27. 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.

28. 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.

29. What does the evidence tell u

30. 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.