Quasars and Distant Galaxies Term Paper
- Length: 5 pages
- Subject: Astronomy
- Type: Term Paper
- Paper: #67648279
Excerpt from Term Paper :
Quasars and Distant Galaxies
How primeval matter cast with uniformity in all directions by an assumed violent explosion, called the Big Bang, gathered together into vast groups of starts and galaxies that evolved into the universe remains a mystery (Peterson 1990). There have been speculations about its origins, pieced together and offering new standards against which theories could be tested and measured. Some of these speculations involved cosmic strings, global textures and late-time phase transitions, notions too strange to merit acceptance. Cosmologists have to reconcile separate and contradictory observations in explaining the origins of galaxies and the structure of the universe, such as the receding of galaxies from one another and the astonishingly uniform glow of invisible radiation in the universe known as the cosmic microwave background, the left-over heat from the creation of the universe. These observations and the abundance of hydrogen, helium and lithium resulting from the initial explosion give credence to a symmetric, homogeneous, expanding universe and the generally accepted theory that a violent cosmic explosion marked the creation or start of the universe 10 to 20 billion years ago (Peterson).
This theory on the symmetric, homogeneous and uniform evolution is inconsistent with observable clumping of matter into galaxies, clusters of galaxies and "walls" and "bubbles" and the detection of very distant quasars, which indicate that some galaxies already existed when the universe was just less than a billion years old (Peterson 1990). The Big Bang assumption does not fit in, in that it does not allow enough time for the force of gravity to gather ordinary matter, such as neutrons, protons and electrons, into the patterns we see today. But the Big Bang theory has remained unchallenged for want of a viable and acceptable alternative. The cold-dark-matter of the universe theory postulates that a second after the Big Bang, the universe underwent a cosmic burp of rapid "inflation" when it expanded much faster than the normal Big Bang observed today. It has remained the easiest to study, the simplest and most capable of providing strong and concrete predictions. Scientists believe that this standard model will stay until overwhelming evidence builds up against it and they say that this has not been occurred.
I. Galaxies and Quasars
A quasar is an extremely distance, thus old, celestial object, whose power output is several thousand times that of our entire galaxy (Lexico Publishing 2005). A galaxy is any of the numerous large-scale aggregates of stars, gas and dust that constitute the universe. Since the time of Galileo, who first investigated the Milky Way by telescope, the galaxy is composed of stars and has its own "stars island," with the sun as just one of the 100,000 million stars comprising the Milky Way galaxy (Henbert 1984). Many years of detailed study reveal that there are thousands of millions of other galaxies beyond the limit of observable universe. These galaxies are classified into spirals, irregulars and ellipticals. Ours is a spiral galaxy. Most of its matter is not in the form of stars, gas and dust, but in some invisible material filling within and surrounding the galaxy.
Astronomers recognize two different kinds of active galaxy: the "starburst galaxies," which were discovered only in 1983 (Henbert 1984); and the strongest active galaxies with a central "powerhouse," that produces energy equivalent to that of a million millions suns and can also send the energy into space. Most astronomers agree that the only possible source for the concentrated power is the gravitational field around a black hole. As gas goes down into the black hole, up to 40% of its mass can be changed into energy. The theory is that it is possible that all spiral galaxies have a central black hole, but these galaxies are fuelled only 10% of the time.
Exciting news reports poured in that a large number of galaxies grew up quickly even when the universe was still young and that these galaxies were as large as the largest galaxies in the universe today (Cowen 2003). They also said that the oldest and most distant known galaxy and that it was among those, which have been in place and forming stars at a rapid rate when the universe was only 800 million years old. Another great event occurred during the meeting of the American Astronomical Society in Seattle with the discovery of the farthest known quasar. The quasar is so distant that the light it emitted 13 billion years ago -- when the universe was young and galactic structures were still forming -- has now reached the earth. Quasars shine brightly because of the super-massive black hole. The January 23 Nature research provided evidence that these black holes have formed early in the history of the universe and have already eaten up matter only a billion years after the occurrence of the Big Bang. And the following month, a study on cosmic microwave background revealed that the radiation left over from the Big Bang indicated that the universe had already produced stars with enough stars to ionize all the hydrogen in the cosmos only 200 million years after the Big Bang (Cowen).
III. The Modern Infrared Camera and its Findings
The development and use of larger infrared detectors enabled astronomers to see through infrared wavelengths objects previously invisible to human eye (Cowen 2003). These detectors were vital to the observations cosmologists want in studying what lies billons of light years from Earth. Using them, astronomers discovered data that suggested the universe was only 2 billion years old and that some galaxies were already unexpectedly large, with some of them imaging spiral structures similar to ours. The results demonstrate the significance of near-infrared observations in obtaining proper and more accurate data on the earliest phases of the universe. Astronomers say that almost of these surveyed galaxies would have been missed if not for these infrared detectors. The occurrence of a number of large galaxies with spiral structure poses the biggest challenge to the standard model of galaxy formation. Astronomers believe that spiral galaxies formed from a simple process. The standard theory states that each galaxy is surrounded by a halo of slow-moving, invisible cold dark matter.
III. In the Beginning, the Dark Matter?
Cosmologists reported that they had gathered convincing evidence that massive galaxies were already in place when the universe was less than a billion years old and that these had pulled in enough material to produce the cosmos' first massive black holes and fuel the first quasars (Cowen 2003). These cosmologists were quite successful in finding distant quasars with light hundreds of times brighter than the galaxies they were first believed to have resided in. They believe that the brightest quasars are fueled by super-massive black holes, which reside in galaxies a trillion times as massive as the sun. The prevailing cosmological model suggests that galaxies have formed soon after the Big Bang if dark matter makes up most of the mass of the universe. If this were true, huge vast dark-matter halos surrounding each ancient galaxy would have pulled in vast amounts of hydrogen needed to form those super-massive black holes and to fuel quasars. Two cosmologists held that two of the most distant and, therefore, earliest, known quasars strongly suggest this. When confirmed, it will serve as the first observational evidence that quasars are embedded in great halos of dark matter, according to Laura Ferrarese of Rutgers University in Piscataway, New Jersey (Cowen).
With 3,000 of recently discovered quasars used as searchlight on the distant universe, astronomers have been able to study the distribution of the diffuse gas between galaxies with unprecedented accuracy (Cowen 2004). The measurements they have been able to make combine with observations gathered through the faint microwave glow of radiation from the Big Bang and other cosmological findings provide the basis for…