Next, navigate to the following page: https://www.zooniverse.org/projects/mikewalmsley/galaxy-zoo-mobile Click get started. Practice cataloging 30 galaxies. Keep a tally of the number of each galaxy type you categorize.

QUESTION

Lab Exercise: Galaxy Classification

The goal of this lab is to demonstrate the value of high resolution telescopes and to study the different types of galaxies in our universe

Types of Galaxies

Galaxies can be broken down into 3 main types. There are many subtypes of each galaxy type. The three main types are spiral, elliptical, and irregular. In the space below sketch an example of each galaxy type.

Next, navigate to the following page: https://www.zooniverse.org/projects/mikewalmsley/galaxy-zoo-mobile

Click get started. Practice cataloging 30 galaxies. Keep a tally of the number of each galaxy type you categorize.

Spiral                                      Elliptical                                             Irregular

Which galaxy type was the most common you observed?

How did telescope resolution affect how you classified a galaxy?

Using a textbook or other resource, explain the evolution of a galaxy.

Did you notice a difference in the color of elliptical vs. spiral galaxies? If so, what is the reason for this difference? What does this tell you about the types of stars in each galaxy as well as the age of the galaxy?

Did you observe any instances where galaxies were interacting with each other? If so, how were they interacting?

Was there any features that you observed at the center of the galaxies you observed? What does this tell you about the density of the galaxy at its center compared to the rest of the disk?

In our galaxy, most of the mass of the galaxy is actually thought to be located outside the central bulge. We are not able to observe this matter since it does not radiate? Do a little research on your own or with  your group. What are some reasons we believe most of the matter in our galaxy is located outside the central bulge?

ANSWER

The Evolution and Classification of Galaxies

Introduction

Galaxies are vast and complex systems of stars, gas, and dust that exist in our universe. Through the use of high-resolution telescopes, astronomers have classified galaxies into three main types: spiral, elliptical, and irregular. In this lab exercise, we explored the different galaxy types and their characteristics, analyzed telescope resolution’s impact on classification, examined galaxy evolution, compared colors of elliptical and spiral galaxies, investigated galaxy interactions, and explored the density at the center of galaxies. Furthermore, we delved into the distribution of matter within our galaxy’s central bulge.

Galaxy Classification

Spiral Galaxies: These galaxies exhibit a spiral arm structure emanating from a central bulge. They are further classified as barred or unbarred based on the presence or absence of a bar-like feature across the center (Conselice, 2006). The Milky Way is an example of a barred spiral galaxy.

Elliptical Galaxies: Elliptical galaxies are more elliptical in shape, lacking the prominent disk and spiral arms seen in spiral galaxies. They are characterized by their smooth and featureless appearance. Elliptical galaxies range from spherical to elongated shapes, denoted by the E0 to E7 classification.

Irregular Galaxies: Irregular galaxies do not conform to the typical spiral or elliptical structure. They lack a distinct shape and exhibit irregular patterns. Irregular galaxies often arise from gravitational interactions and mergers between galaxies.

Telescope Resolution and Galaxy Classification

Telescope resolution plays a crucial role in classifying galaxies accurately. High-resolution telescopes can reveal finer details and structures within galaxies, enabling astronomers to identify features such as spiral arms, bars, and irregular patterns. Improved resolution allows for a more precise categorization of galaxies, reducing ambiguity and enhancing our understanding of their nature.

Galaxy Evolution

The evolution of a galaxy spans billions of years and involves various processes. Galaxies form through the gravitational collapse of gas and dust clouds. Over time, gravitational interactions between galaxies, as well as mergers, can significantly alter their structure. Spiral galaxies, for example, can transform into elliptical galaxies through collisions with other galaxies, which disrupt their spiral arms and lead to a more spheroidal shape. Such interactions trigger intense star formation, shaping the galaxy’s evolution.

Color Differences in Elliptical and Spiral Galaxies

Elliptical galaxies generally appear redder in color compared to spiral galaxies. This difference arises from the variation in stellar populations and star formation rates. Elliptical galaxies are composed mainly of older stars, which emit redder light due to their lower surface temperature. In contrast, spiral galaxies contain a mix of young and old stars, along with ongoing star formation, resulting in a bluer color due to the presence of hotter, younger stars. The color variation provides insights into the age and types of stars present in each galaxy.

Galaxy Interactions

During the classification process, we may observe instances of interacting galaxies. Galaxy interactions occur when the gravitational forces between two or more galaxies cause them to interact and influence each other’s structures (Alonso et al., 2005). These interactions can trigger starbursts, distort the shapes of galaxies, and even lead to mergers. Tidal forces generated during these interactions can induce the formation of new stars and alter the overall morphology of the galaxies involved.

Galaxy Centers and Density

In some cases, features such as a bright nucleus or bulge may be observed at the center of galaxies. These central regions often indicate a higher density of stars compared to the rest of the galactic disk. The bulge represents a concentration of stars and can have a spherical or elongated shape. The density at the center of a galaxy provides valuable information about its overall mass distribution and the presence of a supermassive black hole, which contributes to the gravitational dynamics within the galaxy.

Distribution of Matter in the Central Bulge

Research suggests that a significant portion of a galaxy’s mass resides outside its central bulge. This matter, often referred to as dark matter, does not emit or interact with electromagnetic radiation, making it challenging to observe directly (Portail et al., 2016). Its existence is inferred from the gravitational effects it exerts on visible matter within galaxies. Observations of galactic rotation curves and gravitational lensing phenomena indicate the presence of this invisible matter, suggesting that the majority of a galaxy’s mass lies outside its central bulge.

Conclusion

Through the exploration of galaxy classification, telescope resolution, galaxy evolution, color differences, interactions, and central density, we gain valuable insights into the vast and diverse nature of galaxies. High-resolution telescopes enable astronomers to uncover intricate details and improve our understanding of these cosmic structures. The study of galaxies contributes to our broader understanding of the universe’s evolution and the complex interplay between gravitational forces, stellar populations, and the distribution of matter within these cosmic entities.

References

Alonso, M. J., Lambas, D. G., Tissera, P. B., & Coldwell, G. (2005). Effects of galaxy interactions in different environments. Monthly Notices of the Royal Astronomical Society, 367(3), 1029–1038. https://doi.org/10.1111/j.1365-2966.2006.10020.x 

Conselice, C. J. (2006). The fundamental properties of galaxies and a new galaxy classification system. Monthly Notices of the Royal Astronomical Society, 373(4), 1389–1408. https://doi.org/10.1111/j.1365-2966.2006.11114.x 

Portail, M., Gerhard, O., Wegg, C., & Ness, M. (2016). Dynamical modelling of the galactic bulge and bar: the Milky Way’s pattern speed, stellar and dark matter mass distribution. Monthly Notices of the Royal Astronomical Society, 465(2), 1621–1644. https://doi.org/10.1093/mnras/stw2819