2. What do you know about the solar system? Have you come across the idea that there are many solar systems in the universe? Our solar system is the one we know the most about. However in 1995, astronomers found a planet orbiting a distant star like our sun. Since then, they have found other solar systems. Astronomers now think that there are many solar systems in the universe. Nevertheless, they do not know whether or not there is life in any of these solar systems. In this module, you will study the solar system as a group of celestial bodies. After the discussion, you will have a short review and an online quiz to evaluate how far you have learned about our solar system.

3. WHAT IS A SOLAR SYSTEM? It is the collection of eight planets and their moons in orbit around the sun, together with smaller bodies in the form of asteroids, meteoroids, and comets.

4. THE SUN The sun is the biggest, brightest, and hottest object in our solar system. The Sun’s diameter is 1,392,000 kilometres or 865,000 miles; that’s 109 times the diameter of the Earth. The sun is made of about 70% hydrogen and 28% helium. Click here for more information about the sun

5. MERCURY Mercury is solid and is covered with craters. Mercury has almost no atmosphere. Because the planet is so close to the sun, Mercury’s surface temperature can reach a scorching 840 degrees Fahrenheit (450 degrees Celsius). Click here for more information about Mercury

6. VENUS Venus is the sixth largest planet. It’s about three-fourths the size of earth. Venus is the hottest world in the solar system. There is no liquid water on its surface today because the scorching heat created by its ozone-filled atmosphere would cause any to boil away. Click here for more information about Venus

7. EARTH Earth is the fifth largest planet and the third from the sun. Liquid covers 71 percent of the Earth’s surface. The Earth has one moon. Click here for more information about the Earth

8. MOON The moon is Earth's only natural satellite The Moon is thought to have formed nearly 4.5 billion years ago Click here for more information about the Moon

9. MARS Mars is the fourth planet from the Sun named after the Roman god of war. Mars has a thin atmosphere that contains mostly carbon dioxide. Mars has two small moons: Phobos and Deimos Click here for more information about Mars

10. JUPITER Jupiter is the fifth planet from the Sun and by far the largest. The Great Red Spot is an oval about 12,000 by 25,000 km, big enough to hold two Earths. Click here for more information about the Jupiter

11. MOONS OF JUPITER Jupiter has four large moons and dozens of smaller ones (there are about 67 known moons so far). Galileo first discovered the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto in 1610, using a 20-power telescope; these moons are known as the Galilean moons.

12. IO IO is a large, rocky, volcanically active moon of Jupiter. Its volcanoes spew out molten sulfur, making Io a very colorful moon. It has a diameter of 1,942 miles (3,636 km), very close in size to our moon. Click here for more information about the Jupiter’s moons

13. EUROPA Europa is a large, dense, icy moon of Jupiter. It is the smoothest object in our Solar System It is slightly smaller than the Earth’s moon. Europa is one of the five known moons in the solar system to have an atmosphere. Click here for more information about the Jupiter’s moons

14. GANYMEDE Ganymede is the largest moon of Jupiter, a large, icy, outer moon that is scarred with impact craters and many parallel faults. Ganymede is the largest moon in the solar system; it is also larger than Mercury It was discovered by Galileo and S. Marius (independently) in 1610 Click here for more information about the Jupiter’s moons

15. CALLISTO Callisto has the oldest, most cratered surface of any body yet observed in the solar system. It has a diameter of about 3,000 miles (4800 km), the second-largest moon of Jupiter; it is roughly the size of Mercury. It was discovered by Galileo and S. Marius (independently) in 1610 Click here for more information about the Jupiter’s moons

16. SATURN Saturn is the sixth planet from the sun and the second largest planet in the solar system. Saturn is made of materials that are lighter than water. If you could fit Saturn in a lake, it would float! Saturn is a gas giant made up mostly of hydrogen and helium. Saturn is big enough to hold more than 760 Earths. Click here for more information about Saturn

17. RINGS OF SATURN Saturn’s ring consist of countless small particles, ranging in size from micrometers to meters. The rings are very thin. Though they’re 250,000km or more in diameter, they’re less than one kilometer thick. Click here for more information about Saturn

18. URANUS Uranus is the third largest planet and the seventh from the sun. Uranus is blue-green because of the methane in its atmosphere. Uranus is one of the giant gas planets. Click here for more information about Uranus

19. NEPTUNE Like Uranus, the methane gives Neptune its color. Neptune's blue color is largely the result of absorption of red light by methane in the atmosphere Neptune's winds are the fastest in the solar system, reaching 2000 km/hour. Click here for more information about Neptune

20. REVIEW AND PRACTICE Now that you have learned the different planets and their moons in our solar system, it is time to have a short evaluation. ARE YOU READY? Yes, let’s start! No, let me go back from the beginning.

21. REVIEW AND PRACTICE If you think you are ready, please click on the selection to see if you got the correct answer. LET’S START!

22. REVIEW AND PRACTICE Question no. 1 Question no. 2 Question no. 3 Question no. 4 Question no. 5

23. QUESTION NO. 1 It is the biggest, brightest, and hottest object in our solar system. a.NeptuneNeptune b.SaturnSaturn c.SunSun d.JupiterJupiter Go back to selections

24. QUESTION NO. 2 It is the fifth largest planet and the third from the sun. a.MarsMars b.EarthEarth c.UranusUranus d.VenusVenus Go back to selections

25. QUESTION NO. 3 It is made of materials that are lighter than water. If you could fit Saturn in a lake, it would float! a.NeptuneNeptune b.SaturnSaturn c.EarthEarth d.JupiterJupiter Go back to selections

26. QUESTION NO. 4 Where can you find the Great Red Spot? a.NeptuneNeptune b.SaturnSaturn c.MercuryMercury d.JupiterJupiter Go back to selections

27. QUESTION NO. 5 On what planet can you find the moons phobos and deimos? a.EarthEarth b.VenusVenus c.MercuryMercury d.MarsMars Go back to selections

29. SORRY TRY AGAIN! CLICK HERE TO GO BACK

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39. DO YOU LIKE TO TRY AGAIN? YES, DO IT AGAIN! NO, THANKS.

40. SEE YOU NEXT TIME