Universe, the whole cosmic system of matter and energy of which Earth, and therefore the human race, is a part. Humanity has traveled a long road since societies imagined Earth, the Sun, and the Moon as the main objects of creation, with the rest of the universe being formed almost as an afterthought. Today it is known that Earth is only a small ball of rock in a space of unimaginable vastness and that the birth of the solar system was probably only one event among many that occurred against the backdrop of an already mature universe. This humbling lesson has unveiled a remarkable fact, one that endows the minutest particle in the universe with a rich and noble heritage: events that occurred in the first few minutes of the creation of the universe 13.7 billion years ago turn out to have had a profound influence on the birth, life, and death of galaxies, stars, and planets. Indeed, a line can be drawn from the forging of the matter of the universe in a primal “big bang” to the gathering on Earth of atoms versatile enough to serve as the basis of life. The intrinsic harmony of such a worldview has great philosophical and aesthetic appeal, and it may explain why public interest in the universe has always endured.
Milky Way
The term Milky Way is used to describe the whole of our galaxy. which is made up of about 100,000 million stars.-The galaxy of the Milky Way includes the Earth, the other planets, and the Sun. the Milky Way is also used to describe the band of light, which stretches across the night sky containing millions of stars. The stars in the Milky Way seem to be close together because we see it from the side.
Galaxy
The Galaxy, with the capital G, is the way scientists refer to the galaxy to which the Sun belongs. This Galaxy can be seen at night as the Milky Way. It is a spiral galaxy and there may be about 2000 billion stars in it. The Sun and the Solar System lie about 28,000 light-years from the galactic center. The Sun takes about 220 million years to orbit once around the center of the Galaxy.
Star
A star is a luminous ball of gas. It very hot, making energy through thermonuclear reaction. A star stays in a stable state by balancing the outward pressure of gas with the inward force of gravity. Scientists think that the stars are born in clusters, formed from clouds of gas and dust. The star will burn for thousands of millions of years until its fuel is exhausted. Then, it may become a Red Giant, a White Dwarf, or it may explode as a supernova, leaving behind a neutron stars pulsar, or a black hole. The nearest star to the Earth is the Sun.
Comet
A comet is 'a minor member of the Solar System. It travels around the Sun in an elliptical orbit that is often very drawn out, or elongated. Most comets have three parts: the nucleus, coma, and tail. The gas and dust tail point away from the Sun. Comets are called short period or long period, depending on how long they take to orbit.
Satellite
A Satellite is a body which orbits round a large body. There are two kinds of satellites. Natural satellites, or moons, have been found orbiting many, many planets. The moon is a satellite of the Earth. Artificial satellites have been placed in orbit delibarately.
THE SOLAR SYSTEM
The Solar System is made up of the Sun, the nine Planets and other objects, like large chunks or rocks called Asteroids, balls of ice called Comets and dust particles All of these things are tied to the Sun by the Sun's gravitational or pulling force.
The Sun The Sun is a giant ball of gas with a core temperature of 15 mil- lion C (27 million °F). Without it, there would be no life on Earth. It is so huge that more than 1.3 million Earth's could fit inside it! The Sun is just one of the billions of Stars in space. It is around 4.6 billion years old. In about another 5 billions years, it will use up all of its fuel and swell up to become a red giant Star, 100 times bigger than its present size. After millions of years, this giant Sun will shrink and become a white dwarf Star. As it cools down, it will loose its shine.
Planets
1. Mercury
Mercury is the closest planet to the Sun. it has extreme hot and cold temperatures that can reach 427°C (800 F) during its long day and -173°C (-280°F) during its long night. Almost the entire planet is covered with craters. It has water and almost no atmosphere, only gases. Scientists sat that life cannot exist on Mercury and that there are no moons.
2. Venus
Venus is the second Planet from the Sun with a surface temperature of 482°C (900°F). It is so hot because its atmosphere works like a greenhouse. Venus atmosphere is primarily made up of Carbon Dioxide with some Nitrogen, traces of water vapour, acids and heavy metals. The sky is like a grand display of constant lightning and thunder. The surface is a great hot desert with no water, but it does have mountains, craters and some active volcanoes. There are no Moons on Venus.
3. Earth
Earth is the third Planet from the Sun and the fifth largest Planet in the Solar System. It is the only Planet that is known to have life. We live on Earth. Energy from the Sun is vital to life on Earth, The Earth is a mass of land, air and sea. It takes 365.25 days for the Earth to orbit the Sun. Earth has only one moon.
4. Mars
Mars is the fourth Planet from the Sun and it has a pink sky, due to the tiny pieces of dust floating in the atmosphere. In 1979, two Viking spacecraft visited Mars, but no sign of life was found. Even though Mars has freezing temperatures, little air and no surface water, it is believed that the Planet could have and can hold life Mars has two Moons.
5. Jupiter
Jupiter is the fifth Planet from the Sun. it is also the largest Planet in the Solar System. It is 1300 times bigger than Earth. Jupiter has at least 16 Moons. It also has the biggest Moons and its biggest Moon is even bigger than the Planet Mercury! Jupiter is a huge ball of liquid with a rocky core. There are many wild wind- storms raging in Jupiter's thick atmosphere. It also has a strong magnetic field, which is five times greater than the Sun's.
6. Saturn
Saturn is the sixth Planet from the Sun and the second largest in the Solar System. It is about 95 times bigger than Earth. Saturn has at least 18 Moons and is well known for its bright rings. Its atmosphere consists of about 97% hydrogen, 3% helium and traces of methane and ammonia.
7. Uranus
Uranus is the seventh Planet from the Sun. it has a magnetic field similar in strength to those around Earth and Saturn. It has 15 Moons and 11. rings. The atmosphere consists of 83% hydro- gen and 15% helium, as well as small amounts of methane and hydrocarbons.
8. Neptune
Neptune is the eighth Planet from the Sun. it is 17 times bigger than earth. It is thought that Neptune consists largely of hydrogen and helium with no apparent solid surface. However, it may have a core that comprises of ice and rocky material. In 1989, the space probe Voyager 2 flew by Neptune, gathering invaluable information about this Planet. Neptune also has an internal heat like Jupiter and Saturn. The Planet's temperature is -213°C (- 352 F). There are eight Moons in Neptune.
9. Pluto
Pluto is the coldest Planet in the Solar System because it is the most distant Planet from the Sun. it is also the smallest Planet in the Solar System. The surface temperature is between-212 C 350 F) and -228 C (380 F). There is only one Moon. Little is known about Pluto.
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