The Earth and Beyond

1. The Earth and Beyond The Solar System The Universe

2. The Solar System - Our Sun The SOLAR SYSTEM is the SUN and all of its SATELLITES. The Sun is a STAR. It gives out LIGHT and HEAT due to NUCLEAR REACTIONS. Our Sun is made up mainly of the elements HYDROGEN and HELIUM, but not all stars are the same. There are many different types with varying SIZES, COLOURS and TEMPERATURES. The satellites of the Sun all ORBIT the Sun because of the Sun’s GRAVITY. The Sun is the MOST MASSIVE object in the Solar System. You should never LOOK at the Sun DIRECTLY as it could damage your eyesight permanently! There are many types of stars.

3. The System of Sol Pluto Can you name them? (Not to scale!) Uranus Neptune Jupiter Saturn Earth Mars Venus Mercury

4. The Planets There are NINE planets in our Solar System. The planets are kept in orbit by a combination of the SUN’S GRAVITY and their SPEED. The Earth takes 365.25 DAYS for one orbit of the Sun. Unlike the Sun, the planets are seen by REFLECTED LIGHT. They move around the Sun, not in circular orbits, but in slightly squashed orbits – ELLIPTICAL ORBITS. The first four planets, the INNER PLANETS, are SMALL and ROCKY: The next four planets, the OUTER PLANETS, are LARGE and GASEOUS: JUPITER MERCURY SATURN VENUS What about Pluto? EARTH URANUS MARS NEPTUNE

5. The Planets There are nine planets in the Solar System. The planets orbit (orbit means to move around in a path) the Sun in slightly elliptical orbits. The planets are similar in some ways, but in others are very different. By looking at each of the planets in turn you can build up a picture of the Solar System as a whole.

6. Mercury Mercury is the closest planet to the Sun. In appearance and size Mercury is very similar to the Moon. Mercury, like the Moon, has a cratered appearance. Mercury has an elliptical orbit and is the second smallest planet after Pluto. During the day the temperature on Mercury reaches 450°Celsius. During the night, due to the lack of atmosphere, the temperature falls to –180°Celsius. These harsh conditions mean that it is unlikely there is life on Mercury.

7. Venus Venus is the second planet moving out from the Sun. Venus is covered in thick clouds as seen from Earth. We have been able to study the surface of Venus using radar mapping. Venus would not be a nice place to visit. It has a surface temperature higher than that of Mercury. This is caused by the ‘Greenhouse Effect’ of the dense Venusian atmosphere which consists mainly of carbon dioxide. If you stood on the surface of Venus you would be incinerated by the high temperatures, corroded by the sulfuric acid found in the atmosphere, suffocated by the lack of oxygen and crushed by the dense atmosphere.

8. Earth The Earth is the third planet from the Sun. It has a surface covered 70% by liquid water and the rest by rock. It has an atmosphere that consists mainly of nitrogen and oxygen. It is also the only place in the Solar System where life is known to exist. The Earth spins once on its axis every 24 hours. This causes day and night on Earth. The Earth is tilted on its axis. It is this tilt that causes the Seasons. It takes the Earth 365.3 days to orbit the Sun once.

9. Mars Mars is the fourth planet from the Sun. Like Mercury, Venus and Earth, Mars is small and rocky. Together these four planets make up the four inner planets. Mars is often referred to as the ‘Red Planet’. This is because it is covered in red dust on the surface of the planet. It was once thought that there was life on Mars. Spacecraft have visited Mars but life has not yet been detected. There is evidence liquid water once flowed on Mars. Liquid water is a requirement for life as we know it. Even though there may be no life on Mars now, there may have been life on Mars in the past. Mars has two moons, Phobos and Deimos. They are thought to be captured asteroids.

10. Jupiter Jupiter is the largest planet in the Solar System. If Jupiter had been eight times more massive then it would not have formed a planet, it would have formed a star. Jupiter does not have a solid surface but is a gaseous planet. Jupiter is famous for its ‘Red Spot’; this is a large storm in Jupiter’s upper atmosphere that is three times bigger than Earth! Jupiter has 16 moons. The four largest are Io, Europa, Ganymede and Callisto. Europa is thought to possess liquid water and it is possible that it could support life.

11. Saturn Saturn is the sixth planet from the Sun and is gaseous in nature. Saturn is famous for its beautiful ring-system. The rings are not solid but are thought to consist of millions of particles of ice. Saturn, like Jupiter, consists mainly of the elements Hydrogen and Helium. Saturn has an overall density that is less than the density of water. This means that if you could find a sea large enough, then the planet Saturn would float. Will Hay, the famous British comedian, was a keen amateur astronomer who discovered a ‘White Spot’ upon the surface of Saturn.

12. Uranus Uranus is the seventh planet from the Sun and is gaseous in nature. Uranus also has a ring-system similar to Saturn. However, the rings of Uranus are thought to consist of dust from the break-up of a moon; perhaps caused by an asteroid collision. Uranus is barely visible to the naked eye and was unknown to ancient peoples. It is clearly visible with a small telescope and has 15 moons. Only five of the moons are visible from Earth – Miranda, Ariel, Umbriel, Titania and Oberon.

13. Neptune Neptune is the eighth planet from the Sun, although for part of its orbit Neptune is the furthest planet from the Sun. Neptune is the fourth gas giant (along with Jupiter, Saturn and Uranus). Neptune has a ring-system and an active cloud-system. The winds on Neptune are thought to reach up to 2 000 kilometres per hour – that is faster than a bullet! One of Neptune’s eight moons, Triton, is unusual. Triton is the only moon of a planet that orbits in a direction opposite to the direction of the planet’s rotation.

14. Pluto Pluto is the ninth planet from the Sun. It was only discovered in 1930 by Clyde Tombaugh. Indeed it was only in 1978 that it was discovered that Pluto has a solitary moon. The moon of Pluto is called Charon. Pluto does not fit the pattern of planets in the Solar System. It is thought to consist of rock and ice. Pluto also has a very elliptical orbit (which is why Neptune is sometimes the furthest planet from the Sun). Some astronomers do not think Pluto is a true planet and is more similar to an asteroid or comet.

15. Exercise 2: The Inner Solar System • Which two elements make up most of our local star? • Why should you never look directly at the Sun? • How many planets are small and rocky? • What do we call these small and rocky planets? • Which planet is closest to the Sun? • Which of these planets supports life? Hydrogen and helium. It could permanently damage your eyesight. Four – Mercury, Venus, Earth and Mars. The inner planets. Mercury. Earth.

16. Exercise 3: The Outer Solar System • Name the four outer planets. • Which is the largest of these four planets? • Name two differences between the inner planets and the outer planets? • Which outer planet has a spectacular ring system? • Which planet is furthest from the Sun for most of its orbit? Jupiter, Saturn, Uranus and Neptune. Jupiter. The inner planets are smaller, rocky, have shorter orbital times and are warmer than the outer planets which are larger, gaseous, have longer orbital times and are cooler. Saturn. Pluto.

17. Exercise 5: Temperatures • Look at the table and graph. What pattern do you notice? What is the exception?

18. Planet Temperatures As you MOVE FURTHER AWAY FROM THE SUN,THE TEMPERATURE OF THE PLANETS DECREASES. This is because they receive less heat energy from the Sun, the further away you get. Some planets have an ATMOSPHERE. This can affect the temperature of the planet. This is why VENUS is HOTTER than MERCURY even though Venus is FURTHER AWAY FROM THE SUN. Venus has an atmosphere that contains GREENHOUSE GASES, they let the Sun’s heat energy in, but will not let it escape; the planet gets warmer as a result. The GREENHOUSE EFFECT. The surface of Venus is hot enough to melt LEAD! The surface of Venus is shrouded in thick cloud

19. Exercise 6: Orbital Time • Use the data below to draw a graph showing how the orbital time of a planet varies with its distance from the Sun. What general pattern can you see?

20. Orbital Times As you MOVE FURTHER AWAY FROM THE SUN,THE ORBITAL TIME OF THE PLANETS INCREASES. This is because the further away a planet is, the greater the distance it must travel to complete one orbit. Remember, the planets’ orbits are ELLIPTICAL not CIRCULAR. An interesting point to note is that even though we say that PLUTO is the planet that is FURTHEST AWAY FROM THE SUN, this is not always TRUE. The orbit of NEPTUNE is partly outside that of Pluto. So, for part of its orbit, NEPTUNE IS THE PLANET FURTHEST AWAY FROM THE SUN. Neptune’s orbit Pluto’s orbit

21. Moons MOONS are the NATURAL SATELLITES of planets. The natural satellite of the Earth is THE MOON. Not all planets have moons. Some planets have one or two, and some planets have lots. Many moons have craters. Why? Our moon is barren and lifeless. Some moons in the Solar System are thought to hold the best chance of finding LIFE; even if it is in primitive form. EUROPA is a moon of JUPITER. Europa is thought to possess LIQUID WATER underneath its icy surface. Liquid water is a requirement for life as we know it, so many scientists feel the BEST CHANCE of finding life in our Solar System is on Europa.

22. Comets Comets are objects that orbit the Sun in HIGHLY-ELLIPTICAL orbits. They are only seen for a SHORT TIME when they are RELATIVELY CLOSE TO THE SUN. Like Planets and moons, comets are seen by REFLECTED LIGHT. Comets are thought to consist of ICE and DUST particles (like a dirty snowball). It was only recently that we discovered the truth about comets when several spacecraft flew close to approaching comets; one craft even passed through the tail of a comet. HALLEY’S COMET is a famous comet that has an orbital period of 76 YEARS. Very few people see Halley’s comet twice in their life and no one ever sees it three times. What is the tail of a comet? Evaporating ice particles as the comet approaches the Sun.

23. Asteroids Between the planets MARS and JUPITER thousands of lumps of rock are found. These lumps or rock are called ASTEROIDS. The region where they are found is known as the ASTEROID BELT. These asteroids have varying and eccentric orbital paths. Some have passed very close to the Earth; in the past some have hit the Earth. Some scientists believe that LARGE ASTEROIDS IMPACTING on EARTH have resulted in MASS EXTINCTIONS in the past. There are several large IMPACT CRATERS on the surface of the Earth thought to have been caused by impacting craters. The Moon has a lot more visible craters than the Earth because the Moon has NO ATMOSPHERE to protect it.

24. Exercise 7: Moons, Comets and Asteroids • What do we call the natural satellites of planets? • Why can we only see comets for a short period of their orbit? • What makes up the tail of a comet? • Where is the asteroid belt found? • How do we see comets, moons and asteroids? Moons. They have highly-elliptical orbits, so for much of their orbit they are in the outer Solar System and too far away to see. Evaporated ice particles as the comet approaches the Sun. Between Mars and Jupiter. By reflected light.

25. The Scale of Things We live on a PLANET called EARTH. The Earth and all the planets ORBIT the SUN. Our Sun is one of many STARS. MILLIONS OF STARS grouped together are called a GALAXY. Our Sun is part of a SPIRAL GALAXY called the MILKY WAY. There are MILLIONS OF GALAXIES, all the galaxies together make up the UNIVERSE. A spiral galaxy

26. Exercise 8: Scale of the Universe Our Sun is a _____. There are many different types of star. _______ of star grouped together are called a _______. Our local galaxy is the Milky Way. The distances between the stars in a galaxy are a lot bigger then the distances between the ______ in our Solar System. There are millions of galaxies; together they make up the ________. The distances between galaxies in the Universe is a lot bigger than the distances between stars in a galaxy. star Millions galaxy planets Universe galaxy Universe planets star millions

27. Exercise 10: Match the Names with the Body The Sun Europa Saturn The Milky Way A moon A spiral galaxy A star A planet

28. Exercise 9: Which… 1. For the following bodies answer the questions below. Galaxy Saturn Asteroid Comet Sun North Star • Which are seen by reflected light? • Which are light sources? • Which are part of our Solar System? • Which two are stars? Saturn, asteroid, comet Galaxy, Sun, North Star Saturn, asteroid, comet, Sun Sun, North Star