Our solar system as we know it is a very mysterious place. Even as we learn about our solar system, the planets that make it up, and all of the stars and other matter that make it up, it is still very hard to come to the reality of what all this actually means. Very few people have the privilege to really understand our solar system and what makes it what it is, these people are astronauts who actually can see it and begin to understand first-hand what is going on beyond our world.
Mercury.
As you travel outward from the Sun, Mercury is the closest planet. It orbits the Sun at an average distance of 58 million km. Mercury is airless, and so without any significant atmosphere to hold in the heat, it has dramatic temperature differences. Mercury is also the smallest planet in the Solar System, measuring just 4879 km across at its equator.
Venus.
Venus is the second planet in the Solar System, and it’s an almost virtual twin of Earth in terms of size and mass. Venus orbits at an average distance of 108 million km, and completes an orbit around the Sun every 224 days. Apart from the size, though, Venus is very different from Earth. It has an extremely thick atmosphere made almost entirely of carbon dioxide that cloaks the planet and helps heat it up to 460 °C. If you could stand on the surface of Venus, you would experience 92 times the pressure of Earth’s atmosphere, with incredibly high temperatures, and poisonous clouds of carbon dioxide and sulfuric acid rain.
Earth
Earth is our home; the third planet from the Sun. It orbits the Sun at an average distance of 150 million km. Earth is the only planet in the Solar System known to support life. This is because our atmosphere keeps the planet warm from the vacuum of space, but it’s not so thick that we have a runaway greenhouse effect. The Earth has a solid core of iron surrounded by a liquid outer core that generates a magnetic field that also helps protect life on Earth from the radiation of space.
Mars
The 4th planet from the Sun is Mars, the second smallest planet in the Solar System. It orbits the Sun at an distance of 228 million km. You might think Mars is large, but it’s a tiny world, with about half the diameter of Earth, and just 1/10th the Mass. If you could stand on the surface of Mars, you’d experience about 1/3rd Earth’s gravity. Mars has almost no atmosphere to help trap heat from the Sun, and so temperatures can plunge below -140 °C in the Martian winter. Even at the height of summer, temperatures can get up to 20 °C in the day – just barely shirt sleeve weather. Mars has two tiny asteroid-sized moons: Phobos and Deimos.
Jupiter
Mighty Jupiter is the biggest planet in our Solar System. It’s so large, in fact, that it has 2.5 times the mass of all the rest of the planets in the Solar System combined. Jupiter orbits from the Sun at an average distance of 779 million km. Its diameter at the equator is 142,984 km across; you could fit 11 Earths side by side and still have a little room. Jupiter is almost entirely made up of hydrogen and helium, with trace amounts of other elements. Jupiter has the most moons in the Solar System – it has 63 moons at last count.
Saturn
Saturn is the 6th planet from the Sun, and the 2nd largest planet in the Solar System. It orbits the Sun at an average distance of 1.4 billion km. Saturn measures 120,000 km across; only a little less than Jupiter. But Saturn has much less mass, and does it have a low density. In fact, if you had a pool large enough, Saturn would float! Of course, the most amazing feature of Saturn is its rings. These are made of particles of ice ranging in size from a grain of sand to the size of a car. Some scientists think the rings are only a few hundred million years old, while others think they could be as old as the Solar System itself. And speaking of moons, Saturn has a total of 60 moons discovered (so far).
Uranus
Next comes Uranus, the 7th planet from the Sun. It orbits the Sun at an average distance of 2.9 billion km. Uranus measures 51,000 km across, and is the 3rd largest planet in the Solar System. While all of the planets are tilted on their axes, Uranus is tilted over almost on its side. It has an axial tilt of 98°. Uranus was the first planet to be discovered with a telescope; it was first recognized as a planet in 1781 by William Herschel. Uranus has 27 known moons.
Neptune
Neptune is the 8th and final planet in the Solar System, orbiting at an average distance of 4.5 billion km from the Sun. It’s the 4th largest planet, measuring about 49,000 km across. It might not be as big as Jupiter, but it’s still 3.8 times larger than Earth – you could fit 57 Earths inside Neptune. Neptune is the second planet discovered in modern times. Neptune has 13 known moons.
And those are the planets in the Solar System. Unfortunately, Pluto isn’t a planet any more. But still, it is very wonderful.
