_EU HW #9 Due April 10, 2022

.docx

School

New York University *

*We aren’t endorsed by this school

Course

MISC

Subject

Astronomy

Date

Apr 3, 2024

Type

docx

Pages

3

Uploaded by GeneralSnowCrane14

Natural Science I:Einstein’s Universe MAP-UA 204 EU HW #9 Due April 10, 2022 1.What was the timescale difficulty that confronted the Big Bang theory? According to the Big Bang model, the age of the universe was less than the established age of stars. 2. Walter Baade helped settle the timescale difficulty by his realization that stars can be divided into two broad categories, called population I and population II stars. What characteristics distinguish these groups of stars? Pop 1 was brighter than Pop 2 Cepheids when Pop 2 had the same period of variation. Astronomers only saw Pop 1 but since they built their distance scale for the Cepheids using the dimmer Pop 2 Cepheids, they wrongly estimated that the distance of the Andromeda Galaxy was closer than it really is. Cepheids, which are variable stars, from Pop 1 are four times luminous than Pop 2 Cepheids with the same period of variation. 3. Specifically, how did Baade’s discovery lead to a resolution of the timescale difficulty? It proved that the distance to the Andromeda galaxy was calculated incorrectly. This also meant that the calculations for distances to other galaxies were incorrect as well. When doubling the distance to that galaxy, it is also necessary to double the distance to other ones too. The universe is 3.6 billion years old. 4. Why does a revised distance measurement to other galaxies lead to a revised age of the Universe according to the Big Bang model? If a galaxy is much further away than is calculated, there would be more distance. 5. Allan Sandage, like his thesis advisor Baade, revised the intergalactic distance scale, but using HII regions within galaxies rather than Cepheid variable stars. What are HII regions, how did they lead to inaccurate distance measurements and how did Sandage revise Baade’s distance measurements? What was the impact of Sandage’s revised distance scale on the age of the Universe? Did it ease or exacerbate the timescale difficulty? Sandage demonstrated that the distance to a galaxy containing an H II region was initially underestimated. He showed this by proving that a galaxy’s brightest stars were actually H II regions glowing gas (which is brighter than the stars). Therefore, the relationship between the age of the universe and the H value is inversely proportional: the smaller the H value, the older the universe’s age is. 6. The stars generate helium from hydrogen at core temperatures of about 10 million degrees. Why does it require even higher temperatures to create elements with greater numbers of protons than helium?
This is because protons, which have positive charges, need more kinetic energy to outperform the increased electrical repulsion. 7. Stars support their weight against gravity by generating energy from hydrogen to helium conversion. What is the next nuclear fusion reaction in a star’s core that generates energy? 3 helium-4 nuclei fuse together. This produces carbon-12. 8. What did Hoyle postulate about the nucleus of carbon-12 that could account for its formation from helium-4 and beryllium-8? Carbon-12 needs the precise mass in an excited form. 9. Carbon-12 is produced from helium-4 via the triple alpha process in the cores of some stars. Why couldn’t this reaction occur in the nucleosynthesis phase of the Big Bang? Helium could turn into beryllium, and in turn, carbon. Therefore, billions of stars from billions of years are capable of creating large amounts of carbon. 10. What is the principle way that elements heavier than carbon (but lighter than iron) are formed inside stars? The principle way for elements which are heavier than carbon to form inside stars is called nucleosynthesis. Nucleosynthesis occurs when simple matter merge together to form stars and galaxies. Then, according to the Steady State Theory, the simple matter was forged in the stellar furnaces into heavier elements. Heavy elements originated from dying stars. Light elements formed not long after the Big Bang. 11. What are the two principle types of supernovae? There are two types: Type 1 and Type 2. A Type 1 supernova is extremely bright and can still be seen even if they erupt in faraway galaxies. You can use spectroscopy to measure their recessional velocity. This will demonstrate that the universe expanded at an increasing rate. A Type 2 supernova will occur towards the end of a large star’s life. This supernova collapses when the nuclear fuel is exhausted. 12. Stars do not fuse elements heavier than iron since such reactions do not release energy. In what stellar phenomena do nuclei heavier than iron form? Nuclei heavier than iron form during explosions of the largest stars. 13. What role is played by neutrons in the formation of nuclei heavier than iron? The neutrons interacted with other particles. They then formed the light nuclei (think helium) and then reacted with other nuclei to form the heavier nuclei.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help