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Galaxy

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The Sombrero Galaxy

A galaxy is a large group of stars and interstellar gas and dust moving around a common center of gravity. The term galaxy comes from the Greek root γαλακτ, galakt, which means "milk" (as in our own Milky Way). There are probably more than one hundred billion (1011) galaxies in the observable universe, which average near one hundred billion stars each. Galaxies range in size from dwarfs with as few as ten million (107) stars up to giants with one trillion (1012) stars.[1]

Contents

Galaxy Structures

There are four known types or structures of galaxies in the universe. Astrophysicists speculate about the existence of unobserved and unexplained dark matter and dark energy in their attempts to explain the nature and function of galaxies.) These celestial bodies are unbelievably ordered and structured as well as the most beautiful looking objects in space.

Barred Spiral Galaxy NGC 1300

Spiral

One of the more common types of galaxies are the spiral or pinwheel shape. These are readily identifiable because of their flat, large disk shapes often with a lot of interstellar matter and recently born star clusters shooting off from the center. The active star formations of the outstretching arms of a spiral galaxy contain many hot, young, blue and blue-white stars making them extremely visible. The young stars in the disk are classified as stellar population I while the older protruding stars as population II. [2]

Although that is a general description of spiral galaxy structures there are also several spiral sub-structure types which can be classified as;

S0 galaxies

These usually are the bridge between ellipsoidals and spirals in that they share properties and characteristics of both. This structure was defined long after the classification system was already established. Usually these types of galaxies have a bright nucleus that is surrounded by a smooth, featureless bulge and a faint outer covering.

Sa galaxies

These normal types of spirals are wound tightly making the arms much closer to the center.

Sb galaxies

The spirals are further spread out and less smooth in appearance with a medium-sized nucleus. Very few observed systems actually exhibit random or chaotic patterns of interstellar dust upon the tightly wound spiral arms. Some actually are smooth with thick spiral arms yet less bright.

Sc galaxies

Sc characteristics include a small center bulge with multiple spiral arms coming from the center very spread out from one another. The arms are more lumpy with bigger pieces of matter almost thicker looking because of the distributed star clouds, star clusters, and gas clouds known as emission nebulae.

Allan Sandage has cited six subdivisions of Sc galaxies that include:

  1. thinly branched arms that wind outward from a tiny nucleus and branch into multiple segments,
  2. multiple arms that start at a bright ring centered on the nucleus,
  3. spiral arms that are poorly defined and that span the entire image of the galaxy,
  4. spiral patterns that cannot easily be traced to the point of origin,
  5. those with thick, loose arms that are not well defined,
  6. and transition types, which are almost so lacking in order that they could be considered irregular galaxies. [3]

Lenticular

Galaxy NGC 5866 (Lenticular)

Lenticular galaxies are also disk shaped. But evolutionists conclude that they represent a more older type of galaxy due to the lack of off-shooting arms which are visible through young, hot stars. Others conclude that the prominent arms are not there because neighboring objects do not posses enough gravity to pull the interstellar matter away from the disk shaped center. Lenticular galaxies' stellar contents (e.g., spectral type) look more like those of ellipticals rather than spirals and have often been misclassified as such.[2]

Elliptical

Elliptical galaxy structures are actually ellipsoidal in shape and from direct scientific observations it is safe to assume that there is actually no global angular momentum. In other words these types of galaxies do not rotate as a whole. The stars still orbit the center but are statistically oriented so that there is little net gain of total angular momentum. Rare observations of disk-like shapes are also seen by scientists, so perhaps ellipticals are at one end of the overarching disk shaped galaxies.[2]

Centaurus A (Elliptical Galaxy)

Irregular

It is thought that since there are no neighboring bodies with enough mass to shape these galaxies due to pull of gravity then they remain irregular in shape. They do not show any disks or ellipsoidal shapes, however a sub-class of disk-shaped galaxies are starting to occur through observations. Irregulars are very important to the study of how galaxies form, in not only the context of creation cosmologies but also through the Big Bang theory. The abundance of nearby examples enables detailed study of their movements. Other such measurements gleaned are occurrences of galactic winds. With their high gas content evolutionists assume that they are similar to younger, more primordial galaxy conditions.[2]

Groups and Clusters

Groups and clusters may contain from ten to thousands of galaxies. The clusters themselves are often associated with larger groups called superclusters.

Groups

This is the smallest form of galaxy aggregation and usually consists of fewer than 10 to 50 galaxies of mixed types spanning roughly 5,000,000 light-years. The group which contains our own galaxy, the Milky Way, is called the Local Group. Groups are assumed to have been formed relatively recently under the creationism model. Following evolutionary cosmology they are only about 10 billion years old.

Clusters

Clusters are larger than groups of galaxies however no clear line between the two can really be established. When observed, clusters appear to be collections of galaxies held together by mutual gravitational attraction, yet velocities are far too great for them to remain gravitationally bound. Other observations through X-ray have shown that galaxy clusters actually contain large amounts of intergalactic gas known as the intracluster medium. This is a very hot gas between 107K and 108K. This gas emits X-rays in the form of bremsstrahlung (electromagnetic) and atomic line emission.

Galaxy clusters usually show these characteristics:

  • 50 to 100 galaxies, very hot gasses emitting X-ray and assumed dark matter.
  • Even distribution of these components throughout the cluster.
  • They have a total 1014 to 1015 solar masses. [4]

Superclusters

Superclusters were not really known until the 1980s when new types of telescopes and sensors were created that let scientists look ever further into the ages-old (according to evolutionists) universe and create three-dimensional images of it. These are groupings of galaxy clusters and were once thought to be the largest structures in nature. However these are now understood as subordinate to the enormous walls or sheets (supercluster complexes) that span more than 5% of the observable universe. [5]

Superclusters are typically seen to be long and rather thin strands of many galaxy clusters, intracluster gases and as evolutionary cosmologists would assume, dark matter as well. [5]

Origin

Assumptions

As recently as 2004 a team of astronomers that included Dr. Povilas Palunas, Dr. Paul Francis, Dr. Harry Teplitz, Dr. Gerard Williger, and Dr. Bruce E. Woodgate used a 158 inch telescope in Chile to peer at the distant edge of the universe. They effectively saw 11 billion years into the past assuming the Big Bang theory is indeed correct. Assumptions implied with such origins science are clear as they would assume they are observing what resulted just 2 billion years after the Big Bang happened.

According to Dr. Woodgate,

... we are looking back four-fifths of the way to the beginning of the universe as a result of the Big Bang.[6]

Observations

What was seen initially at the Siding Springs Observatory in Australia confirmed that indeed the galaxy cluster they saw was real. They were assuming to see groupings of hydrogen, essentially young galaxies that are just beginning to form. Instead what they saw was a magnificent mature galaxy cluster. [7] This cluster is actually in a string formation that is at least 300 million light-years long and 50 million light-years wide. Because of the immense size the astronomers were able to identify 37 unique galaxies and one quasar in the string, but "there are almost certainly far more than this." Dr. Povilas Palunas also said that the "string probably contains many thousands of galaxies."

The real power of this observation, however, is that the team of scientists compared what they found against a supercomputer simulation of the early universe, and that simulation could not produce consistent data to back-up their scientific observations. According to Dr. Francis, "The simulations tell us that you cannot take the matter in the early universe and line it up in strings this large." He also stated that "there simply hasn't been enough time since the Big Bang for it to form structures this colossal."[6]

Conclusion

It can be said that either the universe is vastly older than what was originally predicted by the evolutionary timescale, which is probably the path most of science will follow as naturalistic evolution is supported by the majority of scientists. Or, galaxies actually form more quickly than first predicted and within the context of creationism due to mature galaxies being seen the further we go into space the more we discover that indeed galaxies form much faster than previously thought, and that it is a young universe.

Gallery

See Also

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References

  1. Galaxy by Wikipedia
  2. 2.0 2.1 2.2 2.3 Galaxy by SEDS (Students for the Exploration and Development of Space)
  3. Galaxy Encyclopedia Britannica 2007, Ultimate Reference Suite
  4. Galaxies, Groups and Clusters by Answers.com
  5. 5.0 5.1 Superclusters
  6. 6.0 6.1 Giant Galaxy String Defies Model of How Universe Evolved University of Texas McDonald Observatory
  7. Young galaxies too old for the big bang by Andrew Rigg. Creation 26(3):15, June 2004.

External Links

Creationist

Secular

  • Galaxies University of Cambridge Cosmology
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