There is no evidence when universe was born Initially . However, According to Big Bang theory (most commonly accepted theory among scientist community), An infinitely small and dense hot ball appeared, which gave rise to space, matter and energy. This happened around 13.7 billion years ago .
British Astronomer Fred Hoyle suggested the name "Big Bang" when discussing it on radio programme in 1949 . But he did not agree with the theory !
Stars were a mystery to humans for a long time . They are enormous spheres of plasma , mostly hydrogen and with a small portion of helium . Based on light they emit , experts can ascertain their brightness, colour and tempereature . Due to huge distance from earth , they can only be seen as dots of light , even with the most powerful telescopes .
Stars are born in nebulae-enormous gas clouds,mainly consisting of hydrogen and dust, that float in space . Stars can live millions even billions of years. their size can provide clues about their age : smaller stars tend to be younger, while larger stars are older and closer to perishing, soon to cool down or explode as supernovas !
The explosion of a massive star towards the end of its life is extraordinary. There is a sudden increase in its brightness and enormous release of energy. This is called a SUPERNOVA and it releases, in just 10 seconds, ten times more power than the SUN will release in its entire life .
it is estimated that two supernovas explode each century in the milky way, but last one which was visible with the naked eye occurred in 1604 !
The final stage in the evolution of star's core is the formation of a very compact object, the nature of which depends on the mass that collapses. More massive stars end up as black holes ; these strange objects have such intense gravity that not even light can escape.
The planets, satellites, asteroids, other rocky objects and the vast number of comets that circle the sun comprise the Solar System; Its diameter is often considered to be in the region of two light-years . The elliptical paths of the planets moving around the Sun are known as "orbits". Astronomers have confirmed over 1000 extra solar planets and there are doubtless many more waiting to discovered .
The word "planet" comes from the Greek for 'wandering star" because ancient astronomers watched these bodies moving around in the night sky .
The SUN is almost a perfect sphere, and its mass makes up about 99.86 % of the total mass of the solar system .
Galileo's observations of the phases of Venus, which are only possible because it orbits the sun, were among his proofs that the earth is not the centre of the universe .
The diameter of mars is 6794 km , making it almost half the size of earth and second smallest planet in the solar system .
Triton is the only large moon in the solar system that orbits in the opposite direction to the rotation of its planet .
Scientists have concluded that Pluto forms part of Kuiper Belt, made up of material left over from the formation of the Solar System .
Since the time the Solar System began to form , the fusion , collision and break-up of different materials has played an essential role in the formation of the planets . These "small " rocks are remnants of this process . They are witnesses that provide data to help us understand the extraordinary phenomena that began 4.6 billion years ego . On earth these objects are associated with episodes that would later influence evolutionary processes.
Fragments of rock and metal in are found in a variety of shapes and sizes orbits the Sun .
A 17-m (55ft) wide meteorite entered Earth's atmosphere on 15th February 2013 . Chelyabinsk , Russia, in a 500- kiloton fireball.
Comets are small , irregularly shaped objects, measuring less than a few kilometers in diameter, that are usually frozen and dark in color . Comets are made of dust , rock gases and organic molecules rich in carbon , and can be found orbiting in the Kuiper Belt or the so-called Oort cloud. However , many comets deviate towards the inner part of the Solar System , assuming new paths. When they warm up , their formations sublimate forming their heads and long tails of gas and dust.
Halley's Comet takes approximately 76 years to complete its orbit around the sun , so it will next be visible from earth in 2061 !
The Moon was created when a Mars-sized body crashed into Earth while it was still in formation . The expelled material scattered around Earth and over time , it joined together to form the Moon . It is our planet's only natural satellite , and its gravitational pull influences the tides on Earth . The Moon's influence on bodies of water varies depending on its position .
The body of the water closet to the Moon feels its gravitational pull more strongly , while opposite side of earth is less affected .
The far side of the moon is covered in craters and has only a few small lava seas . It looks very different from the side we can see from earth !
At least four times in a year , the centers of the Moon , the Sun and the Earth fully align , resulting in one of the most attractive astronomical events to the casual observer : an eclipse . Solar eclipses also provide astronomers with an amazing opportunity for scientific investigation and research.
The space exploration started in 1957 with the launch of first artificial satellite . Now days , advances & technology in astronautics have helped develop the autonomous navigation system , by which a ship may orbit a planet by itself. 'Mars Express 'launched in 2003 was powered by solar energy . It explored a number of objectives and took pictures in Mars .
Astronautics came about in the late nineteenth century , when Russian Konstantin Tsiolkovsky (1857-1935)fore saw a rocket to overcome the force of gravity . But the space race began between world powers in 1957 with the launch of first Soviet artificial satellite , SPUTNIK I in 1957.
Rockets are needed to send any device into space , They have enough power to lift their load off the ground and soon acquire the speed needed to escape the effects of gravity and reach outer space . Rockets developed in the first half of the 20th century . Rockets must travel to high altitudes before reaching maximum speed , to escape the drag and overheating caused by atmospheric resistance .
Unlike conventional rockets , the Space shuttle could be used over and over again to launch and repair satellite and as an astronomical laboratory . The US fleet had five (5) space shuttle naming Challenger, Columbia , Discovery , Atlantis and Endeavour . In future NASA planned to carried shuttle functions through 'Space Launch System'.
The space available for broadcast satellites is finite .Satellites works as communications tolls and their position are regulated by the International Telecommunication Union ( ITU) . Geostationary satellites (GEO) maintain a fixed position relative to earth . In contrast , those in low (LEO) and medium Earth orbit (MEO) require monitoring from ground stations . The use of geostationary satellites for telecommunications was predicted by the British science fiction writer , Arthur C. Clarke in 1945 .
Space probes are solar powered unnamed machines equipped with sophisticated instruments that make it possible to study planets, moons , comets, asteroids and sun in detail One renowned probe is the Mars Reconnaissance Orbiter ( MRO) launched to study Mars from close up in 2005. .
The Voyager 1 and 2 space probes were launched by NASA to study outer Solar System in 1977. They reached Saturn in 1980 and Neptune in 1989 respectively. Both are currently continuing on their journey beyond the Solar System. Both probes have become the farthest -reaching artificial instruments launched by humankind into space . New Horizons was launched by NASA in 2006 to study Pluto and the Kuiper Belt , and is expected to become the fifth interstellar probe .
Life on space stations makes it possible to study the effects of remaining in outer space for longer period of time .These stations are equipped with system ,robots instruments , machines , computers, telecommunication devices , oxygen and various life support systems. These stations provide the crew with oxygen and filter their exhaled carbon dioxide.
After the launch of first satellite in 1957 the space around Earth become littered by huge amount of debris. Used Satellite batteries , parts of rockets and space craft orbit around Earth . The danger of these items presence is the possibility of a collision . Surprise to know that these debris travel at speeds ranging from 30000 to 75000 km/h (18600-43000mph).
Space telescopes are artificial satellites sent into orbit to explore and monitor different areas of the Universe. Hubble put in to orbit on 25th April 1990 by NASA ( (USA) and ESA ( European Space Agency) , is managed by remote control . Hubble is operated by astronomers of various countries . The telescope is named in honour of Edwin Hubble , who showed that there were other galaxies beyond the Milky way and that the universe is expanding .
The VLT - Very Large Telescope is most advanced astronomical observatory in the world . it consist 4 telescopes that make it possible . It is operated by a scientific consortium from 15 countries . Its objectives are to find new worlds around other stars. The VLT has enabled astronomers to study violent flares bursting from the supermassive black hole at the centre of the Milky way galaxy.