Our Solar System

Our Solar System

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1. WE live on a planet called Earth, one of eight major planets orbiting a fairly average star called the Sun. The difference between a star and a planet is that a star is a hot body that gives out light of its own, whereas planets are cool and shine simply by reflecting sunlight. Together, the Sun and all the objects that orbit it make up the Solar System. The Solar System is the Sun’s system.

2. The sun is a hub of a huge rotating system of eight planets, their satellites and other small bodies.

3. Eight major planets circle the Sun. These are divided into two groups:The inner Solar System-the small rocky planets (Mercury, Venus, Earth and Mars).

4. The outer Solar System-Sthe massive gas giants beyond the asteroid belt (Jupiter, Saturn, Uranus and Neptune).

5. Apart from Mercury and Venus, all the planets have moons. 

6. In addition, there are dwarf planets, like Pluto, and countless numbers of smaller bodies, including asteroids and comets. 

7. Mercury takes just 88 Earth days to orbit the Sun, but it rotates very slowly-a “day” on Mercury is 58 Earth days long.

8. Mercury has no atmosphere and its arid (dry) surface is scarred by countless asteroid, meteor and comet impacts.

9. Venus is the hottest planet in the Solar System with surface temperatures reaching 462°C.

10. A “year” on Venus is 225 Earth days long, but the planet spins so slowly (and in the opposite direction to the spin of most of the other planets) that it takes 243 Earth days to complete one rotation. This means that one Venus day (rotation) is longer than its year (orbit time).

11. Venus has been called “Earth’s Twin,” because it is so similar to Earth in size, density, mass and location in the Solar System.

12. Earth is the largest of the “terrestrial”, or rocky, planets (12,742 km in diameter), and has the greatest density of any planet in the Solar System. Earth is the only world in the universe where life is currently known to exist. 

13. Our planet only has one moon, with a radius about one quarter of the Earth’s, making it the largest moon compared to its parent planet. 

4. A day on Mars is about 40 minutes longer than an Earth day, and it takes 687 days to orbit the Sun.

15. A day on Mars is about 40 minutes longer than an Earth day, and it takes 687 days to orbit the Sun.

16. Mars has seasons, like the Earth, and polar caps composed of carbon dioxide ice and water ice. 

17. Mars boasts the largest volcano in the Solar System, Olympus Mons, which is 25 km tall (almost three times the height of Mt Everest). 

18. Mars has two tiny moons, Phobos and Diemos, which were discovered in 1877 and appear to be captured asteroids.

19. The largest planet in the Solar System (with an equatorial diameter of 141,000 km), Jupiter is a “gas giant” -a huge ball of hydrogen and helium gas with possibly a small rocky or icy core. 

20. One thousand Earths could fit inside Jupiter. 

2. A day on Jupiter is just 10 hours long, but it takes 12 Earth years to circle the Sun.

22. Jupiter has a ring system consisting of four rings.

23. Sixty-seven moons have been discovered around Jupiter so far. Its four largest moons, which were first seen by Galileo in 1610, are fascinating worlds in their own right. These moons are called Ganymede (which is larger than Mercury), Callisto (a ball of rock and ice) lo (a boiling world of active volcanoes and lava lakes) and Europa (with a cracked, icy shell believed to cover an ocean of liquid water which may possibly harbour life).

24. Jupiter’s most striking feature is the Great Red Spot in its southern hemisphere. This appears to be a huge cyclone which has been raging for at least the past 400 years.

25. Had Jupiter been 10 times larger, it would have evolved into a small star.

26. At least two earths could fit into the Great Red Spot.

27. Saturn takes 10 hours 39 minutes to complete one rotation and 29.45 Earth years to orbit the Sun.

28. Saturn is most well-known for its glorious and complex ring system, which is made up of billions of pieces of water ice ranging in size from a centimetre to chunks the size of icebergs. The rings are very wide (about 100,000 km across), but not very deep, being less than a kilometre thick. 

29. Saturn has 62 known moons, some of which play an important part in shaping the structure of the ring system. 

30. Saturn’s largest moon, Titan, is the second largest in the Solar System and has a dense atmosphere made up of nitrogen and methane.

31. Uranus was the first planet to be discovered using a telescope. It was found by Sir William Herschel in 1781. It is an unusual world, tipped on its side by an ancient impact. 

32. Uranus is unique in that it rotates “on its side.” Its axis of rotation is lies nearly parallel with the plane of its orbit.

33. With an equatorial diameter of 50,000 km, Uranus rotates every 17 and a quarter hours (in a counter-clockwise direction, like Venus) and takes 84 Earth years to complete its orbit of the Sun. 

34. Uranus has a smoggy atmosphere of hydrogen, helium and methane over an icy interior. It has the coldest planetary atmosphere in the Solar System, with a minimum temperature of -224.2°C.

35. Uranus has 13 known rings, made of much darker particles than the rings of Jupiter and Saturn, perhaps the result of the destruction of an ancient moon by an impact.

37. Uranus has 27 known moons. Titania, less than half the size of our Moon, is the largest, but Miranda is the most interesting, with its tortured surface of deep fault canyons, terraced layers, and a chaotic variation in surface ages and features.

38. Neptune, the outermost of the major planets, was discovered by telescope (in 1846, by Urbain Le Verrier and Johann Galle) as the result of mathematical calculations.

39. It is a little smaller than Uranus (equatorial diameter 49,528 km) and similar in  composition, but its atmosphere is wracked by fierce winds (measured at travelling 600m 
per second) and giant storms.

40. Neptune takes 164.8 years to complete an orbit about the Sun, but its day lasts just over 16 hours.

41. Neptune has a thin system of five rings, composed of ice particles and dust grains, and 14 known moons. Triton, the largest moon, has geysers spewing out nitrogen and dust from below the surface.

42. Winds exceeding 1000 km per hour encircle Neptune, making it one of the windiest places in the solar system.

43. Neptune has a “Great Dark Spot” similar to Jupiter’s Great Red Spot. Scientists believe that it is also a cyclone, about the size of the earth.

44. The (dwarf) planet furthest from the Sun is Pluto. It has the slowest orbital speed as well as the longest period of revolution.

45. Like Neptune, Pluto was also discovered mathematically (by Clyde Tombaugh), but not 
until 1930.

46. Pluto has five known moons.

47. Pluto was finally explored in 2015. Amazing images of Pluto and its large moon Charon have revealed two very different icy worlds, with complex and unexpected geology, demonstrating that we still have much to learn about our Solar System.

48. Pluto lies at the edge of the Solar System, more than 40 times farther from the sun than Earth.

49. Pluto takes about 248 earth-years to orbit the sun. 

50. Pluto’s orbit is highly eccentric, and the planet sometimes travels inside the orbit of Neptune.

51.   The planet closest to the Sun is Mercury. It’s the smallest of the eight planets, not a lot bigger than our own Moon, and like the Moon it’s a rocky body without air or water.