User:Akolkar pruthviraj

The material that makes up the Earth did not exist in its current form[1] when the universe was formed. The hydrogen, helium, and lithiumwithin this blue-green ball was produced in the Big Bang. Helium and lithium are rare on Earth. The hydrogenis most prominent in the water that covers three-quarters of the Earth's surface. The rest of the Earth's surface is a mixture of carbon, silicon, iron, and other elements that emerge at their high points above the water. These elements were produced in the core ofa star, ejected into space during a supernova explosion, and incorporated into the Earth and its Sun when an interstellar cloud collapsed. Make enough carbon, silicon, and iron required several generations of stars to form and eventually end their lives --- Earth couldn't haveformed much earlier than it did. If you look out into space, this may make us seem lonely. However, there are 6 billion of us to share this speck of space dust. Aside from a lucky few of us that might get to take an interplanetary journey in thefuture (can you imagine sending more than, say 1000people on a 10,000 year journey to another star?), this is where we are going tobe our entire lives. This is where future generations willlive. We seem alone when you look up into space, but here on Earth, we are all in this together.In reality, this doesn't do justice to a on object the size of the solar system thatis millions of times the mass of the Sun, and that is devouring a hundred Suns every year. The light that emerges from the matter falling into the black hole maybe able to push yet more gasout of colliding galaxies. Therefore, galaxy collisions are thought to be an enormous factor in how a galaxy evolves. The difficult task for astrophysicists is understanding how often these collisions occur, and what the galaxy will look like when the collision is done. We have a rough idea, but the details require making complex computer observations, and comparingthe results to galaxies that we are lucky enough to see at various stages of their collisions.So much energy is produced that the white dwarf is blown apart. The explosion is seen by astronomers as a supernova. It always has thesame energy, because the white dwarf that produces it is always the same mass, 1.4times the mass of the sun. The image above is actually of one of these "Type Ia" (read, "type one a") supernova, the death of a white dwarf. The main thing astrophysicists don't understand is how nature adds mass to a white dwarf. There are two competing ideas, both of which rely on the fact that stars often come in pairs. One idea is that the explosion is produced when the white dwarfs that descend from a pair of stars merge. However, only a few of thesepairs of white dwarfs are known in our Galaxy, and they will take a very long time to merge. The mergers may not occur often enough to explain the number of Type Ia supernovae that areobserved. The other idea is that some white dwarfs manage to shred the second star in their pairs, and collect those stars' matter ontheir surfaces. Thousands ofthese bizarre pairs have been identified in our Galaxy (depending upon how they are found, they are called cataclysmic variables, dwarf novae, or classical novae). However, for these systems,there is controversy as to whether matter will collect onto the white dwarf, or whether smaller explosions will eject all the collected matter from the surface. In the end, astronomers are pretty certain that white dwarfs can explode, but don't know which white dwarfs end up exploding. Nonetheless, the supernova that result from exploding white dwarfs are a useful tool to astronomers, becausethey all put out about the same energy, and they can be seen from vast distances across the Universe. Astronomers use these supernova to measure distances. In the same way that one can tell how far away a ship is at night by the brightness of its running lights, one can tell how far a Type Ia supernova is by howbright it appears to Earth-bound astronomer.kapuakolkar.evission.com