Galaxies are one of the most interesting things to study because they hold answers to some of the biggest questions in our universe. But just like any science course, galaxies have their own unique set of obstacles that often prevent people from learning about them. How are rotation curves of spiral galaxies determined beyond radii where starlight can be detected? Does galaxy morphology change in the same way regardless of how far or how close galaxies are to us? How do star clusters form and attain such high masses? Are there any correlations between linear momentum and gravitational lensing? What is the history of the formation of galaxies?
There are many questions that can be answered by studying galaxies, but they remain unanswered due to a lack of data. This is where I come in. I am currently writing a paper on galaxy formation, as part and parcel with my research at NASA as an undergraduate student at The Ohio State University. My goal is to use NASA data from the Spitzer Space Telescope to understand how galaxies formed during their earliest stages through today.
1. Galaxies are beyond our reach.
Galaxies are simply too far away for us to have an understanding of them. The light we receive from these galaxies spans billions of years, and that’s not even the entire life-time of the galaxy (as mentioned in the preface). Our most modern telescopes at present, such as the Hubble Space Telescope, are designed to be able to see objects as close as 5,000 light years away because they were originally designed in the 1970s. Our Hubble is only able to view objects out to about 8,000 light years because it was not built with a direct focus on galactic distances.
In comparison, the Andromeda Galaxy is at least 230,000 light years away (1) which means that we are only able to view it as it was 230,000 years ago. If galaxies were closer than 5,000 light years away, we could get a better understanding of their morphology and the nature of their formation. One attempt to overcome this obstacle was using the Chandra X-ray Observatory in part with an all-sky survey for bright X-ray sources in order to look for “super clusters” as far as 12 billion light years away. Because X-rays are able to travel through gas and dust, this allowed for viewing a large amount of distance between galaxies. However, there are many obstacles that prevent us from getting a good look at the universe, but it just means that we have to try harder in our future endeavors in order to overcome these obstacles.
2. We need more data from which to draw conclusions from.
There are many galaxy surveys that have been conducted in the past 20 years, but they all have their shortcomings. This is because we cannot view every aspect of galaxies, due to limitations with our telescopes and equipment. For example, we are only able to view objects of a certain brightness. Some galaxies may be less active than others, but because we cannot detect them due to limitations in brightness, many surveys leave out these galaxies that could answer many questions.
Also, some surveys are not able to look at all wavelengths of light (one example is ultraviolet). This means that some information is left out in the dark when we cannot see it. One survey that has made excellent observations of galaxies was the Sloan Digital Sky Survey, completed in 1991 and published in 2001. It is one of the most complete survey in existence today; however it has left out galaxies located at very high redshift (z > 4). This is because redshift surveys are not able to see these galaxies due to their extreme distances and small size.
3. We have fallen into the same trap that was present in the early 1900s.
In the early 1900s, astronomers made mistakes when they saw a large amount of data; this led them to believe that all galaxies were spirals (2). This idea fit well with many people’s expectations about how galaxies should look like. The spiral shape could explain dark matter and perhaps even the formation of stars, but many physicists were not convinced by this idea. Because of this lack of knowledge and data, we can only assume that most galaxies are spirals now, especially in part due to our limited view at present time.
As we continue to conduct surveys and gather more data, it is important that we do not fall into the same trap as astronomers in the 20th century. For a long time, astronomers had trouble determining the rate of expansion of the universe because they did not have enough data from which to make conclusions. Galaxies are currently our largest source for studying the expansion rate, but there are many other sources such as supernovae.