Our solar systems consists of a huge star we call the sun. The planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto are circling around the sun. The sun is the richest source of electromagnetic energy in the solar system. The sun’s nearest neighbour is a red dwarf star called Proxima Centauri, which is four and a half light years away. The whole solar system, together with the stars you can see on a clear night, is our home solar system. A spiral space of 200 billion stars we call the Milky Way. The Milky Way has two small galaxies nearby, which is visible from the southern hemisphere. They are called the Large Magellanic Cloud and the Small Magellanic Cloud. The nearest large galaxy is the Andromeda Galaxy. It is a spiral galaxy similar to the Milky Way, but it is four times as huge and is two million light years away.

The Sun contains 99.85% of all material in the solar system. The planets only have 0.135% of the material of the solar system. Jupiter contains more than twice the material of all the other planets together. Satellites of the planets, comets, asteroids, meteoroids make up the remaining 0.015%. Under you can see the material distribution in our Solar System.

SUN: 99.85%

PLANETS: 0.135%

COMETS: 0.01%

SATELLITES: 0.00005%

METEOROIDS: 0.00002%

The terrestrial planets are the four inner planets in the solar system is Mercury, Venus, Earth and Mars. They are called terrestrial because they have a compact, rocky, rough surface like the Earth’s. The planets, Venus, Earth and Mars have atmospheres. Mercury has none.

Jupiter, Saturn, Uranus and Neptune are known as the Jovian planets, because they are all gigantic compared with Earth, and a sparkling nature like Jupiter’s. The word Jovian means Jupiter-like. The Jovian planets are also known as the Gas Giants.

Space history

From our small world we have gazed upon the cosmic ocean, the sky, for thousands of years. Ancient astronomers observed spots of light that appeared to move among the stars. They called the objects planets, and named them after Roman deities- Mercury, the messenger of the gods. Venus, the goddess of love and beauty. Mars, the god of war. Jupiter, king of the gods. Saturn, god of agriculture. Uranus, king of the sky. Neptune, king of the ocean and Pluto, king of the netherworld. The stargazes also observed comets with sparking tails, and meteors or shooting stars falling from the sky.

Science grew fast during the European Renaissance. Fundamental physical laws leading planetary movement were discovered, and the orbits of the planets around the Sun, we were able to calculate. In the 17th century, astronomers develop a new kind of instrument which they called telescope. The new event made it easier for astronomers to observe the sky.

The years since 1959 the mankind have explored many things about our solar system that we didn’t knew the answer to. This time since 1959 is called “the golden age of our solar system exploration”. The advanced technology in rocketry after World War II made it possible for the machines to break through Earth’s gravity and travel to the Moon and other planets.

Because the advanced technology, our machines have orbited and landed on Venus and Mars, explored the Sun’s environment, observed comets, asteroids and scanned the surface of Mercury, Jupiter, Saturn, Uranus and Neptune.

These travellers have given scientists much more knowledge and understanding of the solar system. But it is still a lot of mysterious aspects we don’t know the answer to…

The Sun

The Sun is the most famous element in our solar system. It is the largest object and contains approximately 98% of the total solar system mass. One hundred and one Earths would fit across the Sun’s disk, and its centre could hold over 1.3 million Earths. The Sun’s outer visible cover is called the photosphere and has a temperature of 6000 Celsius.

Solar energy is created deep inside the centre of the Sun. The temperature here is 15,000,000 C and the pressure is 340 billion times Earth’s pressure at sea level. Because of the high temperature and the incredible intense pressure, nuclear reactions take place. This reaction causes four protons or hydrogen nuclear which together make up one single particle or helium nuclear. The energy created in the Sun’s core takes a million years to reach its surface. Every second, 700 million tons of hydrogen are transformed into helium ashes. In the process, 5 million tons of pure energy is released and this is the reason why the Sun is becoming lighter and lighter.

The chromosphere is above the photosphere. Solar energy passes through this section on its way out from the center of the Sun. Everywhere on the Sun you can see sunspots. Sunspots are dark spots on the photosphere with a typical temperature of 4000 C.

The corona is the outer part of the Sun’s atmosphere. It is in this region that prominence appears. Prominences are immense clouds of glowing gas that explode from the upper chromosphere. The outer region of the corona extends far into space and consists of particles travelling slowly away from the Sun. the corona can only be seen during total solar eclipses.

The Sun appears to have been active for 4,6 billion years and has enough fuel to go on for at least another five billion years. At the end of its life, the Sun will start to emit helium into heavier elements and begin to grow so large that it will swallow the Earth. After a billion years as a red giant, it will suddenly collapse into a white dwarf, similar to the final end of any star we can see on the sky. It may take a trillion years for the Sun to cool off completely.

Mercury

The Romans named Mercury after the fleet-footed messenger of the gods because it seemed to move more quickly than any other planet. It is the closest planet to the sun, 58 million kilometres, and second smallest planet in the solar system. Its diameter is 40% smaller than Earth and 40% larger than the Moon (4670 km). It is even smaller than Jupiter’s moon Ganymede and Saturn’s moon Titan. Mercury has only 88 earth days and no satellite.

The planet has very thin air which consists mostly of helium. The temperature on the surface at day is about 430 Celsius, at night -150 Celsius. The physical structure and the chemical composition of the surface are like the one on the Moon.

If an explorer walked onto the surface of Mercury, he would discover a world similar to lunar terrain. Mercury’s rolling, dust covered hills have been damaged from the constant shower of meteorites. The explorer would notice that the sun seemed to look two and a half times larger than on Earth. The sky on Mercury is always black because the planet has no atmosphere to spreading light. As the explorer look out into space, he would see two bright stars. One cream coloured, Venus, and the other as blue coloured, Earth.

Earth is the third planet from the sun at a distance of 150 million kilometres. It takes 365.256 days for the Earth to travel around the sun and 23.9345 hours for the Earth to rotate 360o .

It has a diameter of 12.756 kilometres. Our atmosphere is composed of 78% nitrogen, 21% oxygen and 1% other constituents.

Earth is the only planet in the solar system that got intelligent life. Our planet’s fast spin and the melted nickel-iron core, along with the atmosphere, protect us from dangerous radiation coming from the sun and other stars. Earths atmosphere defend us from meteors, most of them burn up in the atmosphere before they can strike the surface.

Saturn

Saturn is the sixth planet from the sun and it is the second largest planet in our solar system with an equatorial diameter of 120 kilometres. You can see that the poles of Saturn are flatted. This is a result of the very fast rotation of the planet on its axis. One day on this planet is about 10 hours and 40 minutes long, and it takes 30 Earth years for Saturn to travel around the sun. The atmosphere is basically composed of hydrogen with small doses of helium and methane. Saturn is the only planet, which is less dense than water, about 30 percent less.

The winds blow at high speeds on Saturn. Near the equator, it reaches speeds of 500 meters a second. The winds blow mostly in an easterly direction. The strongest winds are found near the equator and the speed falls of regularly at higher latitudes. At latitude greater than 35 degrees, the winds exchange east and west as latitude rises.

Saturn’s ring system makes the planet one of the most beautiful objects in the solar system. The rings are spitted into a number of different parts, which include the bright A and B rings and a weak, not so bright C ring. The rings have different gaps. The most important gap is the Cassini Division, which divides the A and B rings. The rings are divided after its brightness. The A ring is brightest. The rings composition is not known for certain, but it seems that the rings might contain or consists of water. They may be composed or icebergs or “snowballs” from a few centimetre to a few meters in size.

Saturn has 18 named satellites and more than 12 other unknown satellites that have been given provisional names. It appears that at least six of them are real satellites. This brings the total number of satellites up to 24 and will probably grow.

Mars is the fourth planet from the sun. Mars is called The Red Planet. The rocks, dirt and sky have a red or pink colour. The red colour was first discovered by stargazes many years ago. It was given its name by the Romans in honour of their god of war.

Before space exploration, astronomers thought that Mars was the best alternative to search for life. Astronomers thought that they saw straight lines were made at the surface. This led to a theory that it was canals that had been built by intelligent beings.

Another reason to expect life on Mars had to do with the seasonal colour change on the planet’s surface. This phenomenon led to speculations that the vegetations was flowering in the warmer months and stopped flowering during colder periods.

The lack of air and no water on the surface reduce the chance to find intelligent beings on Mars. The planet is very could and the temperature seldom get higher than zero. Scientists have a theory that Mars could have been warmer many years ago, if this is right, it would be water at the surface and simple forms for life lived there.

Uranus

Uranus is the seventh planet from the sun and is the third largest in the solar system. It was William Herschel who discovered it in 1781. It has an equatorial diameter of 52 kilometers and orbits the sun once every 84 Earth years. The length of a day on Uranus is 17 hours and 14 minutes. Uranus has at least 21 moons. The two largest moons are, Titania and Oberon. William Herschel discovered them in 1787.

The atmosphere of Uranus is composed of 83% hydrogen, 15% helium, 2% methane and small amount of acetylene and other hydrocarbons. It is the methane in the upper atmosphere that gives Uranus the blue-green colour. The atmosphere is arranged in to clouds that are running at constant latitudes.

Venus, “the jewel of the sky”, was once known by very old astronomers as the “morning star” and “evening star”. Ancient astronomers once thought that Venus had two separate bodies. Venus is named after the Roman goddess of love and beauty, and it is covered by thick swirling clouds.

Astronomers refer to Venus as Earth’s sister planet. Both are almost similar in sizes, mass, density and volume. But the kinship ends here. Venus is very different from the Earth. Venus has no oceans and is surrounded by a heavy atmosphere composed primarily of carbon dioxide with almost no water vapour. Its clouds are composed of sulphuric acid droplets. At the surface the pressure is 92 times stronger than on the Earth at sea level. The temperature is 482 Co. This high temperature is primarily due to the greenhouse effect caused by a heavy atmosphere of carbon dioxide.

A Venusian day is 243 Earth days. Mysteriously, Venus rotates from east to west. To an observer on Venus, the Sun would rise in the west, and set in the east.

Until just recently, Venus dense clouds cover has prevented scientists from exploring the geological nature of the surface. Today radar telescopes and radar systems orbiting the planet have made it possible to see through the thick clouds which cover Venus.

Venus’ surface is relatively young geological speaking. The exploring showed that the surface have been completely resurfaced 300-500 million years ago. The Venusian topography consists of vast plains covered by lava and mountains or highlands caused by deformation.

Venus is marked by numerous impact craters distributed evenly over its surface. Small craters less than 2 kilometres in diameter are almost non-existent due to the heavy atmosphere on Venus. The exception occurs when large meteorites explodes just before crashing. Volcanoes and volcanic types are even more numerous. At least 85% of the Venusian surface is covered with volcanic rocks. Huge lava flows, more than hundreds of kilometres in length, have flooded the lowlands creating vast plains. It is more than 100.000 volcanoes on Venus.

The mountains which is more than 2.5 kilometres are unusually bright. Liquid water does not exist on the surface and cannot account for the bright highlands. One theory proposes that the bright material might be composed by metallic compounds. Studies have shown that the material could be iron pyrite, also known as “fools gold”. This is the reason that Venus is called “The jewel of the sky”.

Neptune

Neptune is the farthest planet of the gas giants. It has an equatorial diameter of 19,500 kilometres. If Neptune were empty, it could contain nearly 60 Earths. Neptune orbits the sun every 165 years. It has eight satellites. A day on Neptune is about 16 hours. The planet was first discovered on September 23. 1846, by the German astrologer, Jahann Gottfried Galle, of the Berlin Observatory, and Louis d’Arrest, an astronomy student.

Two thirds of Neptune is composed of a mixture of melted rock, water, liquid ammonia and methane. The last third is a mixture of heated gases full of hydrogen, helium, water and methane. It is the gas, methane, which gives Neptune its blue colour.

Neptune is a dynamic planet with several large, dark spots important of Jupiter’s hurricane, which are like storms, alike the ones on Earth. The largest spot, known as the Great Dark Spot, is about the size of the Earth, and it is similar to the Great Red Spot on Jupiter. The long bright clouds in Neptune’s high atmosphere are almost like the clouds on Earth. The strongest winds on any planet were calculated on Neptune. Most of the winds there blow westward, and this is opposite to the rotation of the planet. Near the Great Dark Spot, some winds blow up to 2000 kilometres an hour.

Neptune has eight satellites and one day and night is 16 hour at Neptune. The planet has a set of four rings that are thin and very weak. The rings are made up of dust particles that have been made by tiny meteorites smashing into Neptune’s moons. In the rings, it turned out to be bright spots or clumps. The cause of the bright clumps is unknown.

The planet Pluto was first discovered in 1930. Today Pluto is the only planet that has not been visited by a spacecraft and therefore it is many questions we don’t know the answer to. We can’t even tell what kind of atmosphere it has.

Pluto is usually farther from the sun than any of the nine planets in our solar system. However, strangely enough, it is closer to the sun than Neptune for 20 years out of its 249 years orbit. Pluto crossed Neptune’s orbit January 21. 1979, Pluto comes near the orbit September 5. 1989, and it remain within the course of Neptune until February 11. 1999. This will not happen again until September 2226.

Pluto’s rotation period is 6.387 days, the same as its satellite Charon. The usual for a satellite to travel in a synchronous orbit with its planet, Pluto is the only planet to rotate synchronously whit the orbit of its satellite. This means that Pluto and Charon always face each other as they travel through space.

Unlike other planets, but similar to Uranus, Pluto rotates with its poles almost in its orbital plane. When Pluto was first discovered, it was the bright south polar section we could see from the Earth. But Pluto become visible to grow not bright as our viewpoint slowly changed from nearly pole-on in 1954 to nearly equator-on in 1973. Pluto’s equator is now the view seen from Earth.

During the period from 1985 through 1990, Earth was associated with the orbit of Charon around Pluto so we could see an eclipse every Pluto day.

The first eclipses began blocking the north polar section. Later eclipses blocked the equator section, and final eclipses blocked Pluto’s south polar section. The eclipses lasted as much as four hours and by carefully timing their beginning and ending, sizes for their diameter were taken.

Pluto’s icy surface consists of 98% nitrogen. Methane and traces of carbon monoxide are also present. The solid methane indicates that Pluto is colder than -240 C. this planet is the coldest on in our solar system. The atmospheric pressure assumed for Pluto’s surface is 1/100,000 that of Earth’s surface pressure.