Our Smaller Friends- Asteroids and Comets

Asteroids and Comets are the leftovers from the formation of our Solar System. When we think of the Solar System, we tend to think of the Sun, its eight planets, and their moons. But there is much more going on here than meets the eye. The empty spaces of our solar system are littered with small objects known as asteroids and comets. These objects can be thought of as the leftovers of the Solar System. There are chunks of rock, ice, or both that are believed to have formed from the primordial matter that originally created the Solar System. Comets have been known since ancient times. This is because they tend to announce their arrival in grand style. As the Sun heats their cores, their long, glowing tails can be seen for weeks as the circle the Sun. These objects were once thought to be omens of disaster. And for good reason, at some point in the future, one of the chunky rocks or icy mud balls may slam into Earth and alter the course of history. Such an impact 65 million years ago is widely believed to have killed off the dinosaurs. 

Comets are essentially large balls of rock and ice. Many astronomers refer to them as "dirty snowballs" or "icy mud balls"  because that is exactly what they look like. The ice that forms a comet can consist of both water as ice and frozen gases. Astronomers believe that comets may be formed from the very material that created the early solar system. Several missions are in the works to return samples from a comet in hopes that they will help us to better understand the history of our solar system. We all think of comets as having a tail. But this tail only forms when a comet gets close to the Sun. As the comet heats up, dust and gas is expelled through cracks and fissures in its surface. This material trails behind the comet where it is illuminated by the Sun. This causes it to glow, forming the tail that comets are famous for. 

While there are perhaps trillions of comets ringing the outer fringes of the solar system, bright comets appear in Earth's visible night sky about once per decade. Short-period comets such as Halley's were perturbed from beyond the orbit of Neptune and pass through the inner solar system once or twice in a human lifetime. Long-period comets which rings the outer reaches of the solar system, and pass near the sun once every hundreds or thousands of years.

Asteroids are essentially gigantic chunks of rock floating in space. They range in size from a few feet to several miles in diameter. Many asteroids orbit the Sun. Most are located in an area between the orbits of Mars and Jupiter known as the asteroid belt. There are at least 30,000 of these giant boulders in this area, each in it own individual orbit around the Sun. The asteroid belt is somewhat of a mystery. It seems there should be a planet here in this large gap instead of asteroids. Many astronomers believe that billions of years ago a large, rocky planet may have existed here. It may have been blasted apart by some type of cataclysmic event, such as a collision with a large planetoid or even another planet. Another theory states that these asteroids may have formed from the primordial material left over from the formation of the Solar System. The intense gravity of Jupiter may have prevented this material from coalescing into a planet. The asteroids in the asteroid belt range in size form just a few hundred feet to several miles.

 Occasionally, some of these particles may come close enough to the Earth to get caught by its gravity. They may enter the atmosphere as meteors. If they survive the heat of entry and strike the ground, the will be referred to as meteorites. One such meteorite struck Russia injuring more than a thousand by it's shockwaves, the meteorite on the other hand broke to shambles Occasionally, some of these particles may come close enough to the Earth to get caught by its gravity. They may enter the atmosphere as meteors. If they survive the heat of entry and strike the ground, the will be referred to as meteorites. One such meteorite struck Russia injuring more than a thousand by it's shockwaves, the meteorite on the other hand broke to shambles

A Neighborhood Constructed - The Solar System

Throughout the Milky Way, there are clouds of cold gas and dust, just sitting there, doing nothing. At some point in the distant past, this cloud was disturbed; either through the collision of another galaxy, or the explosion of a massive star. The explosion would have sent waves through space that squeezed the gas and dust together. The clumping material was able to attract more material with its gravity, and started to collect into the solar nebula. Just like a dancer that spins faster as she pulls in her arms, the cloud began to spin as it collapsed. The mutual movement of all the atoms in the cloud gave the solar nebula a direction to spin.

 

Eventually, the cloud grew hotter and denser in the center, with a disk of gas and dust surrounding it that was hot in the center but cool at the edges. The Sun formed out of this largest collection of mass at the center of the solar nebula which continued to fall in, the center eventually got so hot that it became a star. As the disk got thinner and thinner, particles began to stick together and form clumps. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planets or moons .

The planets started out as tiny specks of dust that clumped together. As they continued to gather together, they became pebbles, rocks, boulders and eventually planetoids. These planetoids violently collided together to become the planets we know today.

By studying the decay of radioactive elements in meteorites,which are thought to be left over from this early phase of the solar system, astronomers have been able to determine that the Solar System formed about 4.6 billion years ago.

When astronomers look out into the Universe, they see other Solar Systems forming at different stages. Some are large clouds of cold dust, others are starting to collapse. Others have accretion disks, and some might even have planets clearing out paths in the dust of the disk. We can’t see the formation of our own Solar System, but we can see it happening everywhere we look, so we assume our Solar System formed in the same way......!!!

Supporters of life- Stars

Stars are bright celestial objects which give out light of their own. A star is formed  from a giant, slowly rotating cloud called nebula which is made up entirely or almost entirely of hydrogen and helium. Due to its own gravitational pull, the cloud begins to collapse inward, and begins to shrink. As it shrinks, it spins more and more quickly, with the outer parts becoming a disk while the innermost parts become a roughly spherical clump. This collapsing material grows hotter and denser, forming a ball-shaped ' Protostar '.When the heat and pressure in the Protostar reaches about 1.8 million  degrees F (1 million degrees C), the atomic nuclei that normally repel each other start fusing together, and the star ignites. Nuclear fusion converts a small amount of the mass of these atoms into extraordinary amounts of energy — for instance, 1 gram of mass converted entirely to energy would be equal to an explosion of roughly 22,000 tons of TNT.

This is like an atom bomb explosion, the difference is that in these weapons the atomic nucleus splits to release energy whereas in stars the nuclei fuse to form energy. Nuclear fusion is much more powerful than nuclear fission.

The reaction happening in a star has immense power, if measured in watts, our sun's luminosity is 400 trillion trillion watts, the luminosity of a star is usually measured in terms of the luminosity of the sun. For example, Alpha Centauri - the closest star after sun - is about 1.3 times as luminous as the sun.

The size of a star is very huge and cannot be measured in meters or even kilometers, therefore they are measured relative to the size of our sun. Stars range in size from neutron stars, which can be only 12 miles (20 kilometers) wide, to supergiants roughly 1,000 times the diameter of the sun.

The sun and other stars are the supporters and giver of life. The life that thrives on planet earth is pretty much because of the existence of sun. The heat from the sun is essential for our survival. All  kinds of sources of energy - food, fossil fuels, wind energy, tidal energy, etc. - are primarly derived from sun. The constituents of our body like proteins, carbohydrate, amino acids cannot be formed without sunlight. It is the sun's gravitational pull that supports the solar system. In the end it would be fair to say that if sun dies (its expected life is more 5.5 million years, so don't be afraid) we all will be killed too.

Birth Of A Mystery

The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10^-34 of a second or so old — that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age — it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light.

Edwin Hubble discovered this phenomenon of the expanding universe by observing a distant galaxy. He observed that the galaxy is constantly moving away from us. His discovery7 is so significant that the world's most powerful space telescope is named after him.

During this inflation period, the universe doubled in size at least 90 times, going from subatomic-sized to golf-ball-sized almost instantaneously. Before the Big bang, the universe was smaller than the size of an atom and made up entirely of energy. This energy during big bang got converted into mass which continued expanding under it's immense energy. This unlikely conversion was proved by Albert Einstein in his energy-mass conversion theory which is also the base of formation of atomic bombs.

After inflation, the growth of the universe continued, but at a slower rate. As space expanded, the universe cooled and matter formed. One second after the Big Bang, the universe was filled with neutrons, protons, electrons, anti-electrons, photons and neutrinos. Which are the base of almost everything we see in this world.