ASTRONOMICAL A look at our solar system Emanuel Santos
THE SOLAR SYSTEM
The solar system is comprised of eight planets, plus billions of particles of rocky and icy debris. The four inner planets are small and made up of rock – these are the terrestrial planets. The four outer planets are, by contrast, gassy giants made up of substances such as hydrogen and helium. The formation of the planets is the result of debris, left over from the explosive birth of the sun, colliding into each other. Debris closest to the sun was heated to become particles of rock and metal, while those further out remained as frozen grains of water, methane and ammonia. Solar nebula, the gaseous substance left over from the sun’s birth, was pulled in by the gravity of the fast growing giant planets to form massive balls of gas. An asteroid belt is found in between Mars and Jupiter, while the icy Kuiper Belt Is found beyond Neptune. These particles are the remaining debris that did not coalesce into planets.
THE SUN
The Sun accounts for 99.8% of mass in the solar system, creating immense amounts of heat and light energy like a nuclear fusion reactor. It is mostly made up of hydrogen and helium, the two lightest elements in the Universe. The Sun also sends out electrically charged particles in solar storms, appearing on its surface as eruptions of light. Areas of magnetic disturbance are visible as dark sunspots where the temperature is cooled. Although its core converts 4 million tonnes of matter into pure energy every second, it takes 100,000 years for the energy to reach the surface and appear as light.
TERRESTRIAL PLANETS
MERCURY
Being the closest planet to the sun, Mercury is naturally very hot, with daytime temperatures reaching 430°C. Despite this, the planet’s atmosphere (so thin it’s called an exosphere) is incapable of trapping heat during the night, causing temperatures to drop to -180°C. Mercury is the only planet to have such extreme temperature swings. It is thought that Mercury may once have had a thick atmosphere, but its small size didn’t provide it with sufficient gravity to keep it from being blown away by solar winds.
VENUS
Despite being the second planet from the sun, Venus is the hottest, averaging a surface temperature of 470°C. Venus appears from space as a cloudy ball due to its incredibly thick atmosphere that blocks out 80% of all sunlight and is drenched with sulphuric acid that evaporates before it even reaches the ground. This extreme temperature is the result of a sort of runaway greenhouse effect, thanks to the atmosphere’s high CO² content. The planet rotates on its axis so slowly that one Venusian day is longer than one Venusian year.
EARTH
Our home world is the only planet in the solar system which allows water to exist in its three physical states: solid, liquid and gas. This is thanks to Earth’s distance from the sun, its gravitational pull and its insulating atmosphere. It is liquid water which allows for the development of life. Earth’s surface is constantly moving and changing due to the slow movement of tectonic plates. Earth’s continents have been sliding, colliding and changing shapes over millions of years. 175 million years ago, Earth was made up of one large super continent known as Pangaea.
MARS
Mars’ signature colour is provided by the large amounts of iron-rich dust on its surface. Though the red colour gives the planet a warm appearance, it is actually a bitterly cold desert land. Volcanoes and rift valleys suggest tectonic forces were once generated by a hot interior, but its core has now cooled and partially solidified. The low temperatures and atmospheric pressure mean that water only exists on Mars as vapour or ice, but dry riverbeds suggest the previous existence of liquid water - and potentially even life.
GIANT PLANETS
JUPITER
While the sun contains 99% of all matter in the solar system, Jupiter comprises nearly all the rest. Mostly composed of hydrogen, Jupiter is a gas giant with interior pressure so intense that 1000km beneath the surface, hydrogen gas is transformed into a liquid, while 20,000km deeper still it tears hydrogen atoms apart, causing it to behave like liquid metal. Jupiter’s defining features are its belts of clouds that run all around it, and the Great Red Spot: a hurricanelike weather system that has persisted for at least 348 years and is twice the size of Earth.
SATURN
Defined by its elaborate ring system, consisting of various icy fragments, Saturn hides a turbulent atmosphere with colossal electrical storms under a cloudy blanket of ammonia. Saturn’s rings are tens of meters thick, but when viewed edge on from far away they are invisible. The naturally reflective nature of the rings allows sunlight to bounce off of them and illuminate the planet’s night side. Saturn’s storms emit radio signals, but also tend to form seasonal ‘great white spots’. These occur roughly every 29 years - the time it takes for Saturn to orbit the Sun.
URANUS
Although it’s not the furthest planet from the Sun, Uranus’ atmospheric temperatures of -224°C make it the coldest planet in the solar system. Uranus is referred to as an ice giant as its main constituents, water, ammonia and methane are frozen this far from the Sun. It is also thought to have a sea of diamonds around its core, with diamond hailstones raining into it. Perhaps Uranus’ most peculiar feature however is the fact that it rotates on its side, evident by its dark, dusty rings.
NEPTUNE
Neptune has a violent weather system, with some of its wind storms exceeding 1,200kp/h. These winds manifest themselves as dark spots like Jupiter’s Red Spot, though the extremity of the winds make them short-lived. Its colour is caused by a deep methane atmosphere, though white clouds of frozen methane can also be found on its surface. Heat and pressure around Neptune’s core is so great that methane is thought to split into its constituent elements, carbon and hydrogen, to create an ocean of liquid diamond. The irregular shapes and orbits of Neptune’s moons make them likely to eventually spiral and collide into the planet.
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