Galaxy, Planets, Globular Clusters

Running head: GALAXY
GALAXY 3

Galaxy
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1. Describe how Harlow Shapley determined that the sun was not at the Center of our galaxy.

Harlow Shapley held that everything in the universe was within the galaxy. The galaxy was large with a length of 300,000 light years in diameter. Furthermore, the spiral nebulae were a cloud of gas located within the Milky Way. The argument was based on the size of Milky Way when observing the globular star clusters. Shapley had determined the distance to one popular globular star. He made an assumption that all the globular stars had the comparable size. He further determined their distances by using their size on the sky. A loose halo was formed around a disk-shaped body by the globular clusters. In his findings, he found that the location of the sun was 50,000 light years from the center of the disk component of the galaxy. Therefore, the sun was not at the center of the galaxy (Shapley, 2015).
2. Compare the differences between galactic and globular clusters.
The globular stars are globule-shaped stars. They cram together across a few hundred light years. They are located in the halo of the galaxy and within the galactic center orbit. The stars are very old ranging from twelve to thirteen billion years. Few of the stars form the cores of the small galaxies. They do not disassociate over time since they are bound gravitationally. Lastly, they are densely packed with thousands of stars. Contrary, the galactic cluster is a group of thousand stars. They are small in size as well as young in age. They are loosely held mutually with each other by gravitational attraction (Rocca-Volmerange et al., 2015).

3. How does the use of H II regions to find a galaxy’s distance differ from the use of Cepheid variables?
The two methods differ completely. First, the H II regions represent regions containing ionized hydrogen. It keeps glowing every day since it is the region on the galaxy where star formation takes place. There is a predetermined relationship between the geometrical size of the brightest H II region and the galaxy absolute magnitude. Furthermore, a relationship exists between the rotational velocity of H II regions and the luminosity of galaxies. The relationship helps in determining the galaxy distance. However, the Cepheid is a class of bright variable stars. There is a significant direct relationship between absolute luminosity and their period. By determining the luminosity, then it becomes easy to determine the galaxy distance by doing the comparison (Rocca-Volmerange et al., 2015).
4. How does the cluster method tell us the mass of galaxies?
Each galaxy in a cluster moves at its pace. Some galaxies move at a higher velocity than others. The cluster of galaxies only exists when the motion of the galaxies balances the force of the gravity. A relationship exists between the weight of the galaxy and its velocity. The first step is to measure the motion of the cluster of galaxies. Once you establish the velocity, it becomes easy to determine the mass (Rocca-Volmerange et al., 2015).

5. What evidence do we have that the center of our galaxy is a powerful source of energy?
There exists Sagittarius A at the center of our galaxy. The Sagittarius contains radioactive materials that emit energy. Equally important, the wavelengths we experience are substantial evidence of the existence of a complex magnetic field present during the star formation. The massive stars died, and eventually formed a supernova. The Sagittarius A is an example of a diminished star that formed into an enormous black hole. The black hole has gravitational potential energy that it can convert into kinetic energy. The conversion occurs when a swirling pool of hot gasses and dust falls into the black hole. The falling dust forms accretion disk on the surface of the black hole (Rocca-Volmerange et al., 2015).

References

Harlow Shapley. (2015). Columbia Electronic Encyclopedia, 6th Edition, 1.

Rocca-Volmerange, B. A., Drouart, G. A., De Breuck, C. A., Chalmers tekniska högskola, I. P., & Chalmers University of Technology, D. P. (2015). Supernova Remnant Mass Accumulated During the Star Formation History Of The Z=3.8 Radio Galaxies 4c41.17 And TN J2007-1316. Astrophysical Journal Letters.