Abstract

Galaxies are plentiful in our universe and understanding them helps us better comprehend the grand scheme of space and time. With evolving technology, making observations is becoming easier than it has ever been in human history.

Introduction

This lab focuses on images of galaxies taken by telescopes beyond Earth’s atmosphere. Observations are made based on the images in order to gain a better understanding of how astronomers collect their information.

Procedure

1. Understand the similarities and differences between the following galaxy classifications:

-Elliptical

-Spiral

-Barred Spiral

-Irregular

-Dark

2. Classify the galaxies on the provided worksheet according to the Hubble scheme.

3. Look at the images of the Virgo Cluster and the Hercules Cluster. Record observations and answer lab questions.

4. Observe the Hubble Deep Field exposure. Record observations and answer lab questions.

Results and Discussion

A. Classification of Galaxies

First, the galaxies from the provided worksheet are classified by Hubble’s classification scheme.

The suspected classification is recorded next to observations regarding color and shape, relative to why the classification was chosen.

Galaxy #	Suspected Classification	Color	Shape
1	Irregular	Blue	Asymmetric w/ clear center
2	Sc	Yellow & blue	Loosely wound arms
3	SBc	Yellow & blue	Elongated nucleus w/ arms
4	Sa	Mostly yellow	Arms around round center
5	E5	Yellow
6	Irregular	Yellow & blue	Asymmetric; no apparent nucleus
7	Irregular	Yellow & blue	Asymmetric; no apparent nucleus
8	Sb	Yellow	Round nucleus w/ arms
9	E0 (peculiar)	Red	Round nucleus
10	Sb	Yellow & blue	Round nucleus and possible spirals
11	Sb	Yellow & blue	Round nucleus w/ arms
12	Irregular	Yellow	Two bluges/possible merger
13	Sb	Yellow, red, & blue	Round nucleus w/ arms
14	Sc	Yellow & blue	Round nucleus w/ loose arms
15	S0	White	Nucleus w/ cloud
16	E0	Yellow	Nucleus w/ cloud
17	E0	Yellow	Nucleus w/ cloud
18	E5	Yellow	Large, elongated nucleus
19	E0	Yellow	Large, round nucleus
20	E3 (peculiar)	Pink	Central nucleus w/ cloud
21	E7	Yellow	Clear nucleus
22	Sa	Yellow & blue	Cloud with possible arms
23	Sb	Red	Round nucleus w/ arms
24	Sb	Red	Round nucleus w/ arms
25	Irregular	Yellow & purple	Comet-like tail
26	SBb	Yellow & red	Barred nucleus
27	Sc	Yellow & blue	Round nucleus w/ very loose arms
28	E7	Yellow	Elongated nucleus w/o arms
29	Sb	Yellow & blue	Round nucleus w/ arms
30	Irregular	Yellow & blue	Comet-like tail
31	SBc	Yellow & blue	Elongated nucleus w/ clear arms
32	E7	Yellow	Nucleus in cloud
33	Irregular	Purple	Ring shape w/o nucleus
34	E0	Yellow	Very distant but round shape
35	Sa (peculiar)	Blue	Round nucleus w/ arms
36	E?	Yellow	Most likely elliptical based on color
37	Irregular	Yellow	Possibly merging elliptical
38	Sb	Yellow & blue	Round nucleus w/ arms
39	SBb	Yellow & blue	Barred nucleus w/ arms
40	Irregular	Yellow & blue	Possibly two interacting elliptical
41	SBc	Yellow & blue	Barred nucleus w/ loose arms
42	S0	Yellow & blue	Spiral w/o arms
43	E0	Yellow	Round nucleus
44	Sc	Yellow & blue	Clear spirals
45	Irregular	Yellow & blue	Asymmetric
46	SBa	Yellow & blue	Elongated nucleus
47	Sc	Yellow & blue	Round nucleus w/ arms
48	S0	Yellow & blue	Like spiral w/o arms
49	Sa	Yellow & blue	Round nucleus w/ arms
50	Irregular	Rainbow	Many colors & asymmetric
51	Irregular	Blue & green	Asymmetric w/ unusual colors
52	Sc	Yellow & blue	Round nucleus w/ arms

B. Clusters of Galaxies

The general three-dimensional shape of a spiral galaxy resembles that of a tortilla with a bubble in the middle. The disk of arms is relatively flat when compared to the bulge in the middle of the galaxy.

The first cluster we observe is the Virgo Cluster.

The largest galaxies of the Virgo Cluster, M84 and M86, are likely elliptical based on their color and shape.

NGC 4438 appears irregular and asymmetric with a long tail. This probably occurred when two galaxies collided.

Other galaxies in the Virgo Cluster can also be classified by type:

            -NGC 4388: Spiral

            -NGC 4413: Barred Spiral

            -NGC 4402: Spiral

            -NGC 4374: Elliptical

            -NGC 4425: Spiral

Next, we observed the Hercules Cluster.

The Hercules Galaxy is somewhat different from the Virgo Cluster. Galaxies here are bluish, implying that it is newer and more active than the Virgo Cluster.

We could find the distances from these galaxies using the apparent brightness. Apparent brightness is equal to the luminosity divided by 4pi times the distance squared. We could calculate the distance to the Hercules Cluster given the apparent brightness and luminosity.

C. Hubble Deep Field

Most of the galaxies in the Hubble Deep Field appear to be spiral or elliptical with quite a few irregular galaxies. The higher number of irregular galaxies as compared to the Virgo and Hercules clusters could be due to the fact that the universe was once smaller. This means there were more collisions between galaxies, as the distances between them was significantly smaller.

Based on the Law of Conservation of Energy, I would assume the spirals and elliptical are approximately equal in age. The rotation is due to the initial rotation of the particles before forming galaxies, rather than the age of the galaxies.

Most of the irregular galaxies in the image are blue. This implies that they are very hot and relatively active. Stars are probably forming from the collision of dust and particles in these irregular galaxies. 

The yellow galaxies are probably older and more fully developed.

Knowing that the galaxies in the Virgo and Hercules Clusters are already 10-13 billion years old, this implies that the irregular galaxies are probably much younger and still active in making new stars.

If the HDF contains nearly 1,500 galaxies in its 1/3600 degree^2 area, then the entire sky, with an angular size of 41,253 degrees^2, likely contains close to 2.2x10^11 galaxies. We can calculate this by cross-multiplying (1,500 galaxies/ 1/3,600 degrees^2) and (X galaxies / 41,253 degrees^2) to solve for X.