At the end of this unit you should:

2. At the end of this unit you should: 1. Be able to distinguish between the different celestial bodies. 2. Be able to describe how stars, moons and planets behave in relation to each other and more widely in their planetary systems. 3. Be able to recall the differences between each of the eight planets of our solar system. 4. Be able to differentiate between comets, asteroids, meteors, meteorites and meteoroids.

3. astronomy asteroid celestial bodies comet Earth exoplanets galaxies gravitationally independent habitable zone Halley’s Comet heliocentric system high mass stars intermediate – long period comet Kuiper Belt low mass stars luminosity Main Belt meteor meteorite meteoroid moon natural satellites nuclear fusion planetary system primary protostars short period comet solar nebula solar system spectral type spiral galaxy sun sun-like stars tidally locked

4. LIGHTBULB QUESTION Did you use terms such as water, atmosphere, air, oxygen and temperature?

5. Individually or in pairs, list as many celestial bodies as you can, and where possible, give an example (e.g. a planet is an example of a celestial body, and Earth is an example of a planet).

6. (a) Which planet has the greatest mass? Jupiter. (b) What planet has the longest day? Venus. (c) Name two or three elements that are common to nearly all. Iron, hydrogen and helium.

7. (d) Suggest a reason why Mercury is the hottest planet in the solar system and why Neptune is the coldest planet (remember: Pluto is not a planet!). Mercury is the closest planet to the sun while Neptune is the furthest planet from our sun.

8. (e) In the spaces given at the end of Table 15.02.01, add in two moons from any of the planets listed and complete all the details.

9. (f) Develop your own mnemonic device to remember the order of the planets from the sun. For example: My Very Elegant Mother Just Served Us Noodles!

10. Stars: Enormous gaseous celestial bodies which generate energy by nuclear fusion. Emit light and heat energy because of this generation of energy.

11. Investigation 15.02.01: Measuring the diameter of the sun and the moon Equipment: Cardboard, aluminium foil, pin, white paper, clear view of the sun and the moon.

12. Investigation 15.01.01: Modelling the expansion of the universe Instructions: 1. Cut a square about 2 x 2 centimetres out of the centre of the cardboard. 2. Place the piece of aluminium foil over the opening and tape it in place at the edges. 3. Using the pin or another sharp point, puncture the foil to produce a small hole. You now have a pinhole viewer. 4. Hold the pinhole viewer so that the light from the sun passes through the hole and falls on a sheet of white paper held behind the hole. Try to make the distance between the pinhole and the paper as large as possible.

13. Investigation 15.01.01: Modelling the expansion of the universe Instructions: 5. Using your ruler, measure: a. The diameter of the image of the sun on the paper. b. The distance from the pinhole to the paper. 6. Calculate the diameter of the sun with this formula:

14. How did you know when to measure the distance of the image on the paper? When a clear, focused image was formed on the white paper.

15. Investigation 15.02.02: Examining the detail of the sun Equipment: Binoculars, clear view of the sun, projector screen/paper, mirror.

16. Investigation 15.01.01: Modelling the expansion of the universe Instructions: 1. Place the binoculars (large lens-side) down on the cardboard and trace the outline. 2. Cut out the traced outline. 3. Mount the binoculars outside on a tripod, aim the large lens end towards the sun and secure with duct tape. 4. Move the binoculars around until the image formed on the ground is as small as possible. 5. Place the cardboard over the top of the binoculars so you have a shadow behind the binoculars and the image. Cover up one of the eyepieces. 6. Using another piece of cardboard, place it behind the binoculars. You should see the image of the sun.

17. 1. How did you ensure that only the image of the sun was produced onto the screen? Binoculars were focused on the sun only.

18. 2. What safety precautions did you take to ensure you did not look directly at the sun? By not looking into the binoculars. Only confirming the image of the sun as displayed on the ground/cardboard. Wearing sunglasses as an extra precaution.

19. 3. Draw a diagram of what details you were able to see of the sun. Remember, you are investigating the finer details of the sun so focus on those rather than just looking at the obvious.

20. Write a paragraph describing the life and death of a star. Be sure to include how a star remains stable. Stars are formed by the condensing of solar nebula into a tight cluster. This creates high pressure and temperature at its centre, which starts a nuclear fusion reaction. The main reaction undergone by the star is the conversion of hydrogen to helium (nuclear fusion). The energy generated from the fusion of hydrogen and helium is then pushed out of the core and radiates into space in the form of an electromagnetic wave. This causes massive pressure to be exerted outwards from the core, meaning that if no equal force is exerted inwards towards the core of the star, the star would continue to grow outwards. To stop a star from continuously growing, gravity is exerting an equal force inwards towards the core of the star. This allows the star to remain stable.

21. Moons: Celestial bodies that orbit another body, called its ‘primary’, e.g. a planet. Also known as satellites.

22. Copy and Complete In this unit I learned that there are many celestial bodies in our universe. All of these celestial bodies can be found in giant gravitationally bound systems called galaxies. These contain planets, stars, dark matter and much more. I also learned that there are three defining characteristics of a planet. First, it must be massive enough to be rounded by its own gravity. Second, it must not be massive enough to cause fusion, and finally it must be gravitationally independentof its neighbours. There are eight planets in our solar system. Starting with the closest to the sun we have Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto was considered a planet, but is now considered a dwarf planet. The creation of all celestial bodies in our solar system can be attributed to solar nebula.

23. Copy and Complete In the search for an understanding of our universe we have discovered other planets similar to Earth called exoplanets. These planets lie within the habitable zoneof its nearest star, which is important as it means liquid water could be present on the planet, which is necessary for lifeto exist. Other celestial bodies that exist in the universe include asteroidsand comets. There are three classes of asteroids. These are: Carbonaceous (C-Type), Silicaceous(S-Type) and Metallic (M-Type). Asteroids are the remnants of a failed attempt to form a planet and are mainly found in the main belt between Mars and Jupiter. Comets are small bodies of icewhich produce bright clouds of dust and gaseswhen they get close to the sun. Comets only have two classes, short period comets and intermediate–long period comets such as Halley’s Comet.

24. 1. From what are our stars and planets made? Solar nebula.

25. 2. What is the name of the zone around a star in which it is possible that liquid water can exist on a planet? The habitable zone.

26. 3. Our galaxy, the Milky Way, is an example of what? A spiral galaxy.

27. 4. What is the biggest asteroid in our solar system called? Ceres.

28. 5. In what belt can you find the majority of asteroids? The Main Belt.

29. 6. Pluto is the largest celestial body in what belt? The Kuiper Belt.

30. 7. In your own words, explain how a star is formed, and how it maintains its size. Stars are formed by the condensing of solar nebula into a tight cluster. This creates high pressure and temperature at its centre, which starts a nuclear fusion reaction. The main reaction undergone by the star is the conversion of hydrogen to helium (nuclear fusion). The energy generated from the fusion of hydrogen and helium is then pushed out of the core and radiates into space in the form of an electromagnetic wave. This causes massive pressure to be exerted outwards from the core, meaning that if no equal force is exerted inwards towards the core of the star, the star would continue to grow outwards. To stop a star from continuously growing, gravity exerts an equal force inwards towards the core of the star. This allows the star to remain stable.

31. 8. Write a paragraph explaining how a star dies. When a star has exhausted the hydrogen in its core, it will start to fuse the heavier elements in its outer layers. Depending on the size of the star, the outcomes will be very different. When a star with a mass of less than half that of the sun has used up all its hydrogen, it will begin to convert its hydrogen in its atmosphere into helium. But the star does not have enough pressure or temperature for fusion to continue and eventually it will just cool and fade into a small black dwarf. When the hydrogen is exhausted, these stars fuse the elements found in their outer shells and eventually become a red giant with some planetary nebula. These stars do have enough pressure and temperature to fuse the helium core and begin expanding again before finally collapsing into a white dwarf star. (Cont.)

32. 8. Write a paragraph explaining how a star dies. High mass stars will undergo contraction and expansion many times depending on their mass. They can produce supergiant stars that have an iron core. If this giant’s mass is still over 1.4 times greater than the mass of the sun, it will collapse to become a neutron star. If the mass of the supergiant is over three solar masses, it will collapse to become a black hole.