Dark Matter: a Basic Understanding

Introduction

Many people, from the inquisitive, to those involved in the astronomical sciences have questioned the existence of Dark Matter. While it is called many things today, I will continue to refer to this unseen substance by its original name, Dark Matter. As it is still a theory being researched today to validate its existence and make-up, the discovery of dark matter was first presented to the world some time ago by two very intelligent astronomers. In coming to understand this matter, some of the most common questions we find ourselves asking are: What is it?

And, How was it discovered? The most difficult question we all seem to face is “Does it really exist? ” While quite tricky, this question is one that each of us have to conclude an answer to on our own. Therefore to start, I will address the more common questions first, and then I will provide my own answer to the question of its existence. Dark Matter: What is it? When first being introduced to Dark Matter, the first question we find ourselves asking is what is it? In and out of the scientific community dark matter is commonly referred to as “the source of extra gravity,” or the “mysterious form of matter that is unseen. A more refined scientific definition for dark matter is “a nonluminous, undetectable, invisible material in the universe that makes up about 70%-80% of its mass. ” In short, dark matter is an unseen form of material that contains its own gravity which affects its surrounding materials; i. e. gases, stellar, and celestial bodies. With truly dedicated astronomers and cosmologists focused on the structure and composition of the cosmos, this brings me to explaining how this invisible matter called “dark matter” was discovered. Dark Matter: How Was It Discovered?

In 1932 and 1933, astronomers Jan Hendrick Oort and Fritz Zwicky were the first to postulate the idea of the existence of dark matter. In studying the stellar motions of stars within the galactic plane of the Milky Way galaxy, Astronomer Jan Oort observed that the rotational velocity of stars on this outermost part of the galaxy (galactic plane) was actually increasing versus decreasing. This in itself presented a reason to question this stellar movement further since, based on Newton’s law of gravity, the rotational velocity of stars should steadily decrease the further they are from the galactic center.

Oort continued his observations on stellar motions, while astronomer Fritz Zwicky carried out his studies and observations on galactic clusters and how they remained gravitationally bound. During Zwicky’s observations, here is where dark matter was discovered on a much more massive scale. Through Zwicky’s research, he found that there needed to be 10 times as much mass as observed in the form of visible light in order to keep galaxies clustered together. This observation was clear to Zwicky, as it had been to Oort, that there was a large sum of mass existing within the cosmos that was simply “non-visible. At this point, astronomers simply referred to this material as “missing mass. ” Being that the peculiar stellar movement counters Newton’s law of gravity, and occurs in the outermost part of the galaxy known as “galaxy halo’s,” both Oort and Zwicky hypothesized that this “dark matter” must exist in a spherical form that enshrouds the outermost part of galaxies, thus keeping them from flying apart. In understanding how this matter was discovered, this brings me to the final and most important question, and that is determining if it really exists.

Dark Matter: Does It Really Exist? The evidence supporting the existence of dark matter today is very convincing, yet in the scientific community, it is still a theory. Giving a definite answer as to whether it exists is solely up to the individual. Despite this, astronomers are continuing to find more convincing information that supports the dark matter theory. For instance, an August 2012 article published in “Science News Today,” discussed evidence of dark matter filaments (fibers or threads of dark matter) discovered by astronomer Jorg Dietrich and his colleagues.

Dietrich and his colleague’s x-ray observations of a pair galaxy clusters called Abell 222/223, revealed a ribbon of hot gas between the clusters. This, along with the galaxies distorted shapes and how light was bent was the first hint of the presence of dark matter. Continued observation of the galaxy clusters revealed a thick cord of invisible matter with a mass comparable to that of a small galaxy cluster. Dietrich states that gas can account for only about 9 percent of that mass, dark matter appears to make up the rest. Conclusion:

In understanding that dark matter is an unseen material which contains its own gravity, the theory alone provides a unique way of understanding the structure of our universe. Most importantly, the work of astronomer’s Jan Oort and Fran Zwicky set the stage for astronomers to seek out and understand possible unseen forces at work within our cosmos. This is exactly what astronomer J. Deitrich and his colleague’s did. While there is a host of significant evidence supporting the theory of dark matter, Deitrich and his colleague’s evidence was eye-opening.

In concluding if it actually exists, in my opinion its presence is already confirmed. Works Cited Jones, Andrew, and Daniel Robbins. “The Universe’s Dark Matter and Dark Energy, String theory for dummies.

Reference

• ” Dummies. com. Dummies. biz. 2012. Web. 14 Nov. 2012. NASA. What is Dark Matter?
• Washington: Institute for Global Environmental Strategies, 23 Feb. 2012. Web. 14 Nov. 2012.
• Powell, Devin. “Dark Matter Filament Illuminated. ” Science News Magazine 11 Aug. 2012: 9+.
• Print. White, Mark. “Rotation Curves. ” Berkeley Astronomy Department. University of California at Berkeley. 2011. Web. 15 Nov. 2012.