What Are Elliptical Galaxies

Galaxies are huge stellar cities and the oldest structures in the universe. They contain stars, clouds of gas and dust, planets, and other objects, including black holes. Most galaxies in the universe are spiral galaxies, much like our own Milky Way. Others, such as the Large and Small Magellanic Clouds, are known as irregular galaxies, due to their unusual and rather amorphous-looking shapes. However, a significant percentage, perhaps 15% or so, of galaxies are what astronomers term as ellipticals. General Characteristics of Elliptical Galaxies As the name suggests, elliptical galaxies  range from spherically shaped collections of stars to more elongated shapes similar to the outline of a U.S. football.  Some are only a fraction the size of the Milky Way while others are many times larger, and at least one elliptical called M87 has a visible jet of material streaming away from its core.  Elliptical galaxies also appear to have a large amount of dark matter, something that distinguishes even the  smallest dwarf ellipticals from simple star clusters. Globular star clusters, for example, are more tightly gravitationally bound than galaxies, and generally have fewer stars. Many globulars however, are as old as (or even older than) the galaxies where they orbit. They llikely formed around the same time as their galaxies. But, that doesnt mean theyre elliptical galaxies.   Star Types and Star Formation Elliptical galaxies are noticeably absent of gas, which is the key component of star-forming regions. Therefore the stars in these galaxies tend to be very old, and star formation regions are relatively rare in these objects. Furthermore, the old stars in ellipticals tend to be yellow and reddish; which according to our understanding of stellar evolution, means they are smaller, dimmer stars. Why no new stars? Its a good question.  Several answers come to mind. When many large stars are formed, they die quickly and redistribute much of their mass during a supernova event, leaving the seeds for new stars to be formed. But since smaller mass stars take tens of billions of years to evolve into planetary nebulae, the rate at which gas and dust is redistributed in the galaxy is very low. When the gas from a planetary nebula or a supernova explosion finally drifts into the intergalactic medium, there is usually not nearly enough to begin forming a new star. More material is needed.   Formation of Elliptical Galaxies Since star formation seems to have ceased in many ellipticals, astronomers suspect that a period of rapid formation must have happened early in the galaxys history.One theory is that elliptical galaxies may primarily form through the collision and merger of two spiral galaxies. The current stars of those galaxies would become intermixed, while the gas and dust would collide.The result would be a sudden burst of star formation, using up much of the available gas and dust. Simulations of these mergers also show that the resulting galaxy would have a formation much like that of elliptical galaxies. This also explains why spiral galaxies seem to dominate, while ellipticals are more rare. This would also explain why we dont see very many ellipticals when we survey the oldest galaxies we can detect. Most of these galaxies are, instead, quasars - a type of active galaxy. Elliptical Galaxies and Supermassive Black Holes Some physicists have theorized that at the center of every galaxy, almost regardless of type, lies a supermassive black hole. Our Milky Way certainly has one, and weve observed them in many others. While this is somewhat difficult to prove, even in galaxies where we dont directly see a black hole, that does not necessarily mean that one is not there. Its likely that at least all (non-dwarf) elliptical (and spiral) galaxies that we have observe contain these gravitational monsters. Astronomers are also currently studying these galaxies to see what effect the existence of the black hole has on their past star-formation rates.   Edited by Carolyn Collins Petersen

Literature Review Social Anxiety Disorder - 1149 Words

COLLEGE OF ARTS, VICTORIA UNIVERSITY MELBOURNE Literature Review Social Anxiety Disorder in Adolescent Unit Title: Research Methods in Counselling Unit Code: APT 6006 Unit Teacher: Renzo Vittorino Student Name: Mirza Khushnood Ayub Student ID: s4530334 05/10/2015 This literature review is conducted to explore the social anxiety disorder, its Etiology, prevalence and finally putting focus on the need of a special treatment for adolescent with social anxiety disorder. Anxiety problems are the most common and widespread mental issues and are an area of interest for the medical as well as psychology researchers. These disorders are related to excess fear and anxiety and associated behavioural problems, where an emotive reaction to an actual or urgent danger is called as fear, while anxiety is thinking about future threat (American Psychiatric Association, 2013). Anxiety is one of the major problems among mental issues since long ago and is common in children as well as adults. 6-20 percent children and adolescents usually face at least one type of anxiety disorder, if they are cautiously diagnosed and are counted merely when the problem interfere with the life of the subject then rate comes down to 6-10 percent (Co nnolly, 2006). Reportedly, more females face anxiety disorders than males all over the world (Stein Vythilingum, 2015). The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013) has divided theShow MoreRelatedLiterature Review : Social Anxiety Disorder1633 Words   |  7 PagesVICTORIA UNIVERSITY MELBOURNE Literature Review Social Anxiety Disorder in Adolescent Unit Title: Research Methods in Counselling Unit Code: APT 6006 Unit Teacher: Renzo Vittorino Student Name: Mirza Khushnood Ayub Student ID: s4530334 05/10/2015 â€Æ' This literature review is conducted to explore the social anxiety disorder, its Etiology, prevalence and finally putting focus on the need of a special treatment for adolescent with social anxiety disorder. 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These effects were larger in within-group interventions than in waiting-list interventions, and follow up studies done up to 12 months after treatment showed a retention of these effects. Generally, the use of cognitive restructuring and exposure was shown to have better results than the useRead MoreThe Average Age Of Onset Of Generalized Anxiety Disorder1310 Words   |  6 PagesThe average age of onset of generalized anxiety disorder is 31 years old. Generalized anxiety disorder affe cts about 6.8 million American adults. This disorder can develop at any point in the life cycle, but the highest risk is between childhood and middle age. Individuals who suffer from GAD can’t relax; they startle easily, and have difficulty concentrating. Often they have trouble falling asleep or staying asleep. Some physical symptoms include fatigue, headaches, muscle tension, muscle achesRead MoreAnxiety And Anxiety Of Anxiety1018 Words   |  5 PagesANXIETY Anxiety is an emotion distinguished by feelings of tension, uneasy thoughts and physical changes caused by anticipation of danger. Anxiety can also be defined as a critical developmental stage related to change, dispute, and perceived control of the environment (Potter and Perry, 2014). Encountering occasional anxiety is a normal lifestyle, as everyone feels anxious from stressful situations that might make him/her nervous or fearful. In fact, mild anxiety might help an individual be more

Ethnographic Methods Free Essays

Examine the advantages and disadvantages of using ethnographic methods for sociological research I am going to look at the advantages and disadvantages of using ethnographic methods for sociological research. Ethnography is in-depth research into people’s lives through the use of primary data such as Observations and Interviews, and also secondary data such as diaries, and official documents. The first method of research I am going to look at is a primary research method that is unstructured interviews. We will write a custom essay sample on Ethnographic Methods or any similar topic only for you Order Now There are a few advantages to unstructured interviews such as; if a researcher is going to conduct and unstructured interview then the participant is more likely to discuss sensitive information with them, this is because they may feel that the interviewer is sympathetic and understanding and so are more likely to open up towards them. Another advantage is that it allows people to explain their answers further if they need to, for example with questionnaires the person answering may not be able to explain why they put that answer, and so their point is not put across as they would like to have been. There are also some disadvantages to unstructured interviews such as it takes time and can cost a lot of money; although this method is very effective at finding out detailed information about a person and their life, it can take a lot of time to conduct an interview and even longer as it is unstructured so the interviewer can ask as many questions as they like; it could cost quite a lot as you might need to hire an office to do so, and if you need to interview a lot of people over a few days the cost could rise very quickly. Also interview bias is another disadvantage; this means that the interviewer can ask questions that can influence the answer, which then affects the outcome of the results. Interviewer bias can be illustrated through the use of leading questions for example â€Å"Do you get on well with your boss? † this question can make the interviewee question their relationship with their boss, and subtly raises the prospect that maybe they don’t get on with their boss. Another method of primary research covert observation, this involves the researcher joining the group that they are studying, and in covert observation the researcher does not tell them or allow them to find out their true identity. There are some advantages to covert observation such as it has high validity, as the researcher gets first-hand information about the people they are studying. This is a major advantage to covert observation because if this was done by someone else it may not be on the exact same topic and so not all the information they need is there. Another advantage of this method is that it avoids the observer effect, which is that people change their behaviour when they know they are being observed, and this would not show a true reflection of what they are really like. Some disadvantages to covert observation is that the participants are unaware of the experiment and so this is an ethical issue, as some people may not have wanted to be a part of the experiment, and if they find out that they are they could try and sue the researcher. Another disadvantage of this method is that the researcher could become influenced by the group and when writing their findings down it could be in favour or prejudiced against the group. How to cite Ethnographic Methods, Essay examples

Debut Albums and Child free essay sample

This is a small play depicting the importance of unity. Here is an old man in a village. He has 4 children. He is worried because his children are always fighting among themselves. Scene: All the children are fighting with each other. Child 1: Father, he (II) does not work at all. He Is very lazy. Child 2: You are lazy and cunning. I hate you. Father, I dont want to live with him, Child 3: Father, he always takes away my things.Child 4: Dont lie in front of father. Father, he is a liar. Father: Children II Enough. For God sake stop flitting. Come here. (They all come near him) Father: Each one of you go and get a stick from our backyard. (They all come back with a stick) Together: Father, we have the sticks. Father: Now, break them in to pieces. Children: Yes, we did. That was so easy. Father: Now, tie all those pieces together with a string. We will write a custom essay sample on Debut Albums and Child or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Children: Here it is ready. Father: Now try to break it. Children: Father!! Its not breaking. Its strong now. Father: All of you learn from this simple example. You could break them when they were single but could not even bend them when they were together.