ASTR 1303 Final

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El Paso Community College *

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1103

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Astronomy

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Apr 3, 2024

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docx

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Uploaded by PresidentSteelMule26

Alcala 1 Denisse Alcala John Olgin ASTR 1303 12/07/2023 FINAL 1. Refer to an HR Diagram. Where would this star fall along the diagram? Describe the physical characteristics of this star using the HR diagram. The HD 162862 color is orange to red according to the HR diagram. Since the object gives off most of its light at a wavelength of about 4823. 15 Angstroms. This is near the border between the orange to red portions of the spectrum. It is not part of the Apus con- stellation outline but is within the borders of the constellation. The HD 162862 is a giant star. The shell layers of a red giant have been pushed so far out that they can cool into the red spectrum by the red giant's core, which is hot enough to fuse helium and other heavier elements. Because larger stars emit more light energy, they attribute their high luminosity to their size rather than their high temperature.

Alcala 2 2. Using your own, hand-made sketches/diagrams, illustrate how this type of star evolved. Then trace out the "life trajectory" (i.e. evolution) that this star will undergo - from current conditions up to its death. At each major transition, describe the star's state (i.e. temperature, size, etc). Then describe the 5 states of equilib- rium of a star like HD 162826. Like the sun, it evolved just the same way. It started with the gravitational collapse of a molecular cloud. This time it has size of 100 R sun with luminosity 10^4 L sun but tem- perature was lower like 3000K (A to B and C). When temperature reaches to 10^7 K in the core, the fusion reaction started, and star is in main sequence (C to D). In main se- quence, for mass 1.1 Sun, fusion of Hydrogen takes place. The radiation pressure gener- ated by the fusion balances the gravitational contraction and Star maintains the same size. With time increasing, the luminosity of the star increases. Star then follows a horizontal path (D to E) and becomes sub-giant like 10 to 100 times bigger. As star started to fuse helium with gain size, it becomes a ‘red giant’ with size like 100 Rsun with decreased temperature but increased luminosity of 100 to 10^4 Lsun. The temperature of the outer layer increases (F to G). With time, the outer layer expands, and it is left as the hot core, which is not generating energy, so it cools down with time and becomes a white dwarf and heat is lost, a black dwarf of helium and carbon (G to H). The five states of equilib- rium for this star are Hydrostatic Equilibrium, Thermal Equilibrium, Radiation Equilib- rium, Convective Equilibrium, and Chemical Equilibrium.

Alcala 3 3. What are the at least three key pieces of evidence that proves that the Big Bang Theory is true? The Big Bang theory predicts that as the universe expanded and cooled after the initial explosion, leftover radiation should still be detectable today. This radiation, known as the CMB, Cosmic Microwave Background. The further away the galaxy, the greater the red- shift, suggesting that all galaxies are moving away from each other, which is consistent with the expansion of the universe predicted by the Big Bang. Observations show that the abundance of light elements like hydrogen and helium matches the predictions of the Big Bang, while heavier elements are much less abundant. This suggests that these heavier elements were formed later in stars and supernovae after the Big Bang. 4. What is the super-galactic structure called Laniakea? Laniakea is the name given to the supercluster of galaxies that contains our Milky Way galaxy. The name means "immense heaven" in Hawaiian and was chosen to reflect the vastness of the supercluster. The discovery of Laniakea provides new insights into the large-scale structure of the universe. It shows that galaxies are not randomly distributed but are instead organized into vast superclusters and filaments.

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Alcala 4 5. Based on the most recent class lecture, describe the different stages of the universe as it progresses into the future. Use illus- trations to help with your description. The different stages of the universe’s progression into the future are We are currently in the Stelliferous Era, characterized by the existence of stars, galaxies, and cosmic struc- tures. During this time, stars continue to form, evolve, and eventually die, releasing ele- ments into space that conclude of the stellar evolution and the galactic evolution. The universe is expanding, and this expansion is accelerating due to dark energy. This means that galaxies are moving away from each other over vast cosmic distances. This is where the dark era, the degenerate era, the black hole era, and the end all take place. The end is what is theorized that the universe may ultimately reach a state of maximum entropy, where there's no more potential for change or activity, resulting in a cold, dark, and life- less cosmos.