All About Nebulas Clouds of Gas and Dust in Space

A nebula (the Latin word for cloud) is a cloud of gas and dust in space and many can be found in our galaxy as well as in galaxies across the universe. Because nebulas are involved in the birth and death of stars, these regions of space are important to astronomers seeking to understand how stars form and expire. Key Takeaways: Nebulas Nebula refers to clouds of gas and dust in space.The most familiar nebulas are the Orion Nebula, the Ring Nebula, and the Carina Nebula.Astronomers have found nebulas in other galaxies in addition to the ones in the Milky Way.Some nebulas are involved in star formation while others are the result of star death. Not only are nebulas a crucial part of astronomy for astronomers, but they make interesting targets for backyard observers. Theyre not as bright as stars or planets, but they are incredibly beautiful and are a favorite subject of astrophotographers.  Some of the most intricate and detailed images of these regions come from orbiting observatories like the Hubble Space Telescope. A star-forming region called Mystic Mountain in the Carina Nebula. Its many peaks and fingers hide newly forming stars. NASA/ESA/STScI Types of Nebulas Astronomers divide nebulas into several major groups. One of these is the H II regions, also known as large diffuse nebulas. H II refers to their most common element, hydrogen, the main component of stars. The term diffuse is used to describe the large and irregular shapes associated with such nebulas. Nebulas and the Births of Stars H II regions are star-forming regions, places where stars are being born. It is very common to see such a nebula with flocks of hot, young stars within it. Those nebulas may be referred to as reflection nebulas since their clouds of gas and dust are illuminated by—or reflect—the light given off by these bright stars. These clouds of gas and dust may also absorb radiation from stars and emit it as heat. When that happens, they can be referred to as absorption nebulas and emission nebulas.   The Trifid Nebula, a star-forming region in the constellation Sagittarius, is shown here in full glorious color provided by the European Southern Observatory. Smaller telescopes will not show these colors, but a long-exposure photograph will.   European Southern Observatory There are also cold, dark nebulas that may or may not have starbirth occurring inside them. These clouds of gas and dust contain hydrogen and dust. So-called dark nebulas are sometimes referred to as Bok globules, after the astronomer Bart Bok who first observed them in the early 1940s. They are so dense that astronomers need specialized instruments to detect any heat coming from them that may indicate the births of stars.   The Horsehead Nebula is part of a dense cloud of gas in front of an active star-forming nebula known as IC434. The nebulosity of the Horsehead is believed to be excited by the nearby bright star Sigma Orionis. The streaks in the nebulosity that extend above the Horsehead are likely due to magnetic fields within the nebula. National Optical Astronomy Observatories/Travis Rector. Used by permission. Nebulas and the Death of Stars Depending on the size of the star, two classes of nebulas are created as stars die. The first includes supernova remnants, the most famous of which is the Crab Nebula remnant in the direction of the constellation Taurus. Thousands of years ago, a giant, high-mass star exploded in a catastrophic event called a supernova. It died when it began to fuse iron in its core, which stopped the stars nuclear furnace from working. In a short time, the core collapsed, as did all the layers above it. When the outer layers reached the core they rebounded (that is, bounced) back and that blew the star apart. The outer layers rushed out to space, creating a crab-shaped nebula that is still speeding outward. Whats left behind is a rapidly spinning neutron star, created from the remains of the core.   Hubble Space Telescopes view of the Crab Nebula supernova remnant. NASA/ESA/STScI Stars smaller than the Crab Nebulas progenitor star (that is, the star that blew up), dont die quite the same way. They do, however, send masses of material into space in the millennia before their final death throes. That material forms a shell of gas and dust around the star. After it gently blows its outer layers to space, whats left shrinks down to become a hot, white dwarf. The light and heat from that white dwarf illuminate the cloud of gas and dust, causing it to glow. Such a nebula is called a planetary nebula, so named because early observers like William Herschel thought they resembled planets.   The planetary nebula NGC 6781 as photographed through one of the telescopes of the European Southern Observatory in Chile. This nebula lies in Aquila and can be spotted with a good backyard-type telescope. ESO   How Are Nebulas Detected? Nebulas of all kinds are best detected using telescopes. The best-known exception to this is the Orion Nebula, which is barely visible to the naked eye. Its much easier to observe a nebula using magnification, which also helps the observer see more of the light coming from the object. Planetary nebulas are among the dimmest ones, and theyre also the shortest-lived. Astronomers suspect they only last perhaps only ten thousand years or so after they form. H II regions last as long as theres enough material to continue forming stars. Theyre easier to see because of the bright starlight that causes them to glow.   The star Eta Carinae is a hypergiant in the southern hemisphere skies. Its the bright star (left), embedded in the Carina Nebula, which is a star-forming region in the southern hemisphere sky. European Southern Observatory Best-known Nebulas As well as the Orion Nebula and the Crab Nebula, skygazers keep to observe these clouds of gas and dust should get to know the Carina Nebula (in the Southern Hemisphere Sky), Horsehead Nebula, and the Ring Nebula in Lyra (which is a planetary nebula). The Messier list of objects also contains many nebulas for stargazers to search out.   Sources NASA, NASA, spaceplace.nasa.gov/nebula/en/.â€Å"Nebulae - The Dust of Stars.† Windows to the Universe, www.windows2universe.org/the_universe/Nebula.html.â€Å"Planetary Nebulae.† The Hubble Constant, 3 Dec. 2013, www.cfa.harvard.edu/research/oir/planetary-nebulae.http://skyserver.sdss.org/dr1/en/astro/stars/stars.asp

Propaganda in American Media Essay - 805 Words

Propaganda in American Media One of the greatest revolutions in the twentieth century was not political in nature, however, it aided in many different political revolutions. This revolution was the communications revolution. The twentieth century has experienced one of the greatest changes in means of communication including technologies such as radio, motion pictures, the Internet, advanced communications and most importantly the television. Sadly, political leaders and the government to convince or persuade the masses that their ideas supercede those of others have utilized these technologies. Television, more so than any other form of communication, has been the ultimate tool of the propaganda effort. It is the trustworthiest†¦show more content†¦Therefore, what we mostly see on the screen is what the sponsors promote, which are usually mechanisms to keep society stable. This exactly what American media was doing from the muckrakers of the 20s to the war in Kosovo in the 90s. Let us now look at so me examples of the use of TV as a mean of control over society. Before January 1991, public opinion polls showed that the American public was split into two groups, 50% each, about whether the U.S. should attack Iraq or not. Historians say however, if any anti-war voices had been heard in the mass media at this time, the outcome could have been completely different. The second example turns out to be a tragic one, when we talk about the freedom of speech. After the bombing of Hiroshima and Nagasaki, the pictures of the irradiated Japanese were not made available to the American public until the 1980s. In both cases we see the control of society through TV, by those who control it, and directing society toward a certain destination, which is found to be the way forward for the humanity, and keeping the system together by creating a popular culture based on consumerism; turns out to be a modern way of practicing authority in our lives. 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Pros and Cons of Nuclear Power Free Essays

As a result of the current global warming issues and the ever growing scarcity of our current energy resources we may be forced to resort to nuclear energy. The Department of Energy has already given its support to energy companies who have decided to construct nuclear power plants. It appears that nuclear power is the right course to take, but before this decision is finalised it is important to weigh the multiple advantages and disadvantages of nuclear power. We will write a custom essay sample on Pros and Cons of Nuclear Power or any similar topic only for you Order Now There are many pros and cons, but they weigh up almost equally which makes it a hard decision to choose the right course of action, nuclear power or non-nuclear power. The first step to deciding on the use of nuclear power entails looking at its pros. These advantages include its low carbon emissions, its containable waste products, its low cost technological research, and its abundant supply of energy. Abundant supply of electrical energy at lower costs. Uranium can be used instead of oil to produce electrical energy. A ton of uranium can release significant amounts of energy once it undergoes the process of nuclear fission. By nuclear fission, the mere splitting of atomic nuclei can go into a series of chain reactions that can produce great amounts of energy to be converted into electricity. Coal heated power plants require millions times more fuel to create an equal amount of energy as one ton of uranium. A very low amount of carbon emissions are created from nuclear power. Since there is no fuel burning process involved in a nuclear reactor, the amount of carbon emission released from nuclear power plants is less than a hundredth of the carbon emissions released by the fuel burning power plants such as coal heated power plants. Nuclear wastes can be contained and controlled. This is unlike carbon and other greenhouse gas emissions which are released in the atmosphere beyond human control. Carbon dioxide emissions have been the biggest factor that affect global warming conditions. Nuclear technology entails low cost. The nuclear technology of fission is a natural occurrence that does not require further development or research to produce energy that can be converted into electricity. The splitting of a large nucleus causes a chain reaction of splitting other nuclei and releasing shooting neutrons that can continuously split more atomic nuclei creating energy in the process. The next step includes comparing these pros with cons. These include the possible accidents or disasters, the possible creation of nuclear weapons, the expensive price of creating the nuclear power plant, The disposal and safe storage solution of nuclear waste, and the possible terrorist threat to nuclear power plants and waste disposal sites. Nuclear accidents or disasters have happened and taken place on different occasions in different locations in the past. Two of the most widely known nuclear disasters that occurred are the Three Mile Island reactor in the US and the Chernobyl reactor in Russia. Even the countries of France and Japan have had leakages and accidents. Japan experienced a partial meltdown of uranium core in Ottawa in 1952 and several other accidents afterwards including the well-known Tokaimura incident in 1999. France experienced its first major nuclear disaster in 1992 while the most recent was in July 2008. The latest involved a plant malfunction which caused 30,000 litres of uranium enriched solution to leak into two of France’s rivers. The possible creation of nuclear weapons. The Nuclear Non-Proliferation Treaty provides that every country has a right to undertake nuclear development for peaceful purposes. Many nations have taken its context as including the development of nuclear weapons because they feel threatened by other world powers. India feels threatened by Pakistan, while North Korea feels the same way about South Korea. Even developing countries will consider nuclear weapons to protect itself from possible threats of invasion. The setting up of nuclear power plants is expensive. Based on historical records, the actual costs incurred in building nuclear power plants have always exceeded the initial estimates. A report released by the US Congressional Budget Office in May 2008 disclosed that the actual costs incurred to build 75 existing nuclear power plants reached $144. 6 billion dollars. The estimated average cost of was $45. 2 billion. Nuclear waste disposal and storage solutions still have to be perfected. Nuclear waste is also known as Spent Nuclear Fuel or SNF. At the moment the only ideal system of treating SNF involves keeping them in temporary storage in deep disposal sites in the ground. However, SNF or nuclear waste disposal is still considered unresolved by many because there are no countries involved in deep ground SNF storage. Instead the nuclear waste is stored in dry-cask storages in steel lined silos with no definite disposal destination. Also uranium and plutonium have very long half lives and will take many years in storage to decay. The nuclear waste products are still considered radioactive for at least one thousand years. This could threaten homes and there residents if they have the radiation emissions enter their homes. Nuclear power plants and SNF storage silos are possible targets of terrorist attacks. Similar attacks like those launched by the 9/11 terrorists are likely possibilities which cannot be dismissed. This may seem unlikely but so did the attack on the twin towers. There are equal amounts of pros and cons for nuclear power usage and the decision to switch to it in the future is still uncertain. Although there are advantages such as the low carbon emissions and the large amount of energy produce from one ton of uranium the are still disadvantages including the possible nuclear disasters in the reactors and the possible terrorist threat. Either way it is necessary the choice is made soon otherwise our resources will be used up and we will be in a lot of strife. How to cite Pros and Cons of Nuclear Power, Papers