Sunday, March 22, 2020

Astronomy Final Essay Example

Astronomy Final Essay Number each question here according to its number in the Final Examination document provided by your instructor. 1. (a) Kepler’s 3rd law P^2 = a^3 (P = period in years; a = distance in AU) 75^2 = a^3 a = (75^2)^(1/3) = 17. 78 AU. (b) The further comets are from the sun, the slower they travel; therefore, it spends longer at the further distance. 2. (a) Star B is farther away. Its parallax is less. The closer a star is, the more its position changes against the background as the earth revolves around the sun. That is what parallax is. (b) 20 parsecs. One parsec = distance at which a star has a parallax of 1 arcsecond) Since this parallax is 1/20 as large, its distance is 20 times greater. (c) 65. 2 light years. (1 parsec = 3. 26 ly * 20) 3. (a) 10m would have the greater light gathering power (b) Both of the telescopes are in vacuum. The 10m one has area Pi r ^2, with r = 5m and the 2m one has r = 1. The ratio of Pi 5^2/Pi 1^2 = 25. Twenty-five times more light falls onto the l arge telescope. (c) The 10m telescope has a â€Å"Greater† light gathering power. (d) The factor would be about 25 times the light gathering power. e) Normally, light gathering power ratios are just the ratios of the areas. Due to the atmosphere on earth, there could be some absorption, however, since the wavelength is not specified, it wouldn’t hold true. Since the atmosphere acts like a gradient index lens, the amount of light that hits the earth telescope would have a very small increase thus refracting light towards the telescope. If there were no atmosphere, it would have continued at a larger angle and missed the telescope. 4. (a) d = 10,000 =100Mpc 100 (b) d = V d = 10,000 = 200Mpc H0 50 c) If universe is flat and composed mostly of matter, then the age of the Universe is 2 3H0 In the case of a very low density of matter the extrapolated age is larger. Age of universe = 1 H0 So the Universe is directly proportional to H0 5. Gx = GMm/r^2 G_new = GMm / (3r)^2 = GM m / 9r^2 (a) The force is 1/9 times (b) 9 times weaker 6. 15000/3000)^4 (a) The blue star is 625 times (b) more luminous Essay (Answer all nine Questions) Complete these answers in your own words. Follow instructions in the Final Examination document. Answer all questions according to the instructions. Number each question here according to its number in the Final Examination document provided by your instructor. 1. a. H-R Diagram A (Very Young Cluster) b. H-R Diagram D (Young Cluster) c. H-R Diagram B (Old Cluster) d. H-R Diagram C (Very Old Cluster) Similar to the sun, stars will spend a majority of their life on the main sequence. We can view this by looking at the H-R diagram, which shows a ‘dense concentration’ of stars along a constricted belt from the upper left to the lower right. The mass of the star determines where on the main sequence it is located and how soon the star will move away from the main sequence. We will write a custom essay sample on Astronomy Final specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Astronomy Final specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Astronomy Final specifically for you FOR ONLY $16.38 $13.9/page Hire Writer The age of the cluster can be estimated by viewing a cluster of stars on the HR diagram in reference to where they end on the main sequence. 2. Seasonal variation of a planet depends on the frequency with which any given side of the planet changes its position with respect to the star. For a planet like Uranus, which has a high tilt (73 deg), the same side always faces the sun and hence its always summer on one side and winter on the other. Thus we can conclude that seasonal variation is directly related to the tilt of the planet. 3. a. Among the given planets, D has the minimum tilt – So the answer is D, which shows max seasonal variation. b. A planet will be geologically active if it has a high density, since that would assure wide variety of rocks and minerals and ores and less amount of hot gases; so among the planets, A has the highest density and is the most geologically active. 3. The younger surface would go to Moon A due to the fact that Moon B possesses many craters, which are clearly visible as the picture represents (this is clearly shown by the illuminated spots). Genesis shows that the craters were developed over time. Since moon A has far less craters, this means it was recently formed thus making it the younger moon. 4. a. The Hubble Expansion: As the distance increases, the apparent brightness of the object decreases meaning it becomes darker the farther away it gets. This technique determines the relative distances of similar objects. In addition, a phenomenon called the Doppler effect can be used to determine the velocity of an object. The sonic Doppler effect is caused by compression of sonic wave fronts, which can be generalized to electromagnetic radiation and other wavelike phenomena. The magnitude of an objects Doppler shift is a function of its radial velocity relative to the observer. Velocities of various objects, such as stars and galaxies, have been tabulated in our vicinity. An almost straight line with positive slope was obtained when the distance was plotted for various galaxies against their velocities. This shows us that the farther away an object is, the greater the velocity. This lends support to the Big Bang theoryif the universe does indeed expand in a manner consistent with the Big Bang model, then two objects that are close to each other should have smaller relative velocities than in comparison with distant objects. b. Cosmic Microwave Background (CMB): This is the result of theorized energetics, which was discovered in 1965 by Penzias and Wilson. Their discovery showed microwave radiation emanating from all directions in our observable locality of the universe. As predicted by the Big Bang Model, the universe is filled with plasma at high temperatures. As a result, hydrogen can only exit as plasma with an ambient temperature of about 3000K. c. Primordial abundance of light elements: This is the observed abundance of elements in the universe. Examinations through the spectra of various objects shows us that helium makes up about 23% of observable mass in the universe, which is entirely too large to be accounted for by stellar fusion. Since stellar nucleosynthesis makes the abundance of lighter nuclei hard to explain, the Big Bang model theorizes that the nuclei were created during the fierce explosion. . Due to the numerous negative effects on the body, human space travel remains physiologically difficult. Many of these affects are due to long-term weightlessness. Examples include: muscle atrophy, skeletal deterioration, slowing of cardiovascular functions, red blood cell production decrease, balance disorders, and weakening of the immune system. In addition, without the appropriate protection, space exposure becomes a sever threat due to the environmental differences between space and earth – especially the lack of oxygen and pressure. Interstellar space travel consists of many problems, which makes human travel extremely difficult – even in the future. One problem is the amount of fuel needed for long-duration flights. In addition, we have to worry about the damaging effects of galactic radiation. Also consider the loneliness and boredom of generations of humans spending their entire lives aboard a spacecraft. In order to get to the nearest star system beyond our Solar System (Alpha Centauri), we would have to travel 4. 3 ly with a constant flight velocity of 50 km/s; which is roughly about 25,000 years. Although that velocity would allow us to escape the Solar System, it would still take 250 centuries to reach our closest star system. It is very unlikely that humans will be able to equip themselves with the technology, at least anytime soon, to make contact with extraterrestrial life. Even if we took into account the many factors in the Drake equation, galactic civilizations are probably spread out like small islands throughout space. Even if the average lifetime of extraterrestrial civilizations is 1 million years, our most optimistic estimates suggest that each is separated by ~300 ly. Additionally, thousands of sorties would have to be launched toward candidate star systems for any hope of successful extraterrestrial contact. In summary, although it may never become feasible, interstellar space flight is both uneconomical and impractical now and anytime in the foreseeable future. 6. Galileo Galilei was a very influential astronomer because he defended his beliefs in a time when the Roman Inquisition was in power. Galileo defended his idea of heliocentrism against the Inquisition and was put on house arrest. This did not stop him from doing what he loved. While on house arrest, he made observations and continued his work. His contributions to astronomy include the discovery of three moons of Jupiter, the idea that the nature of each planet is unique, identification of sunspots, and his continued examinations of the Milky Way and sea tides. 7. As of March 23, 2012, 763 exoplanets (extrasolar) within our Milky Way have been discovered by satellites such as the Kepler. Consequently, these satellites have been flying through space, uncovering hundreds of new planets within our galaxy. Recently, two planets (Kepler 62e and 62f) have been discovered, which orbit a sun similar to ours but cooler. These planets are at just the right distance that allows water to remain liquid an essential must for a planet to support life. In addition, these planets are very similar to the size of Earth. Because of their size and orbits, it is highly likely that they are either rocky or watery. The two planets are located 1,200 light-years away in a five-planet system orbiting a star dubbed Kepler-62. 8. The milky is a flat disk surrounded by a halo with a bulge at the center. Within the disk, lay clouds of gas and dust that amount to around 15% of the mass of stars. Although we cannot see the nucleus due to all the scattered dust radio, infrared, and x-ray telescopes allow us to see through the dust and show us that the core contains a dense swarm of gas and stars and a massive black hole. A majority of the gas and dust clouds lie within the disk. In addition, bright stars gather into spiral arms winding in an outward direction. The location of our solar system is about 26,000 ly from the center, lying on the inner edge of the spiral arm. 9. D C B A

Thursday, March 5, 2020

The Woman Who Explained the Sun and Stars

The Woman Who Explained the Sun and Stars Today, ask any astronomer what the Sun and other stars are made of, and youll be told, Hydrogen and helium and trace amounts of other elements. We know this through a study of sunlight, using a technique called spectroscopy. Essentially, it dissects sunlight into its component wavelengths called a spectrum. Specific characteristics in the spectrum tell astronomers what elements exist in the Suns atmosphere. We see hydrogen, helium, silicon, plus carbon, and other common metals in stars and nebulae throughout the universe.  We have this knowledge thanks to the pioneering work done by Dr. Cecelia Payne-Gaposchkin throughout her career.   The Woman Who Explained the Sun and Stars In 1925, astronomy student Cecelia Payne turned in her doctoral thesis on the topic of stellar atmospheres. One of her most important findings was that the Sun is very rich in hydrogen and helium, more so than astronomers thought. Based on that, she concluded that hydrogen is THE major constituent of all stars, making hydrogen the most abundant element in the universe. It makes sense, since the Sun and other stars fuse hydrogen in their cores to create heavier elements. As they age, stars also fuse those heavier elements to make more complex ones. This process of stellar nucleosynthesis is what populates the universe with many of the elements heavier than hydrogen and helium. Its also an important part of the evolution of stars, which Cecelia sought to understand. The idea that stars are made mostly of hydrogen seems like a very obvious thing to astronomers today, but for its time, Dr. Paynes idea was startling. One of her advisors - Henry Norris Russell - disagreed with it and demanded she take it out of her thesis defense. Later, he decided it was a great idea, published it on his own, and got the credit for the discovery. She continued to work at Harvard, but for time, because she was a woman, she received very low pay and the classes she taught werent even recognized in the course catalogs at the time.   In recent decades, the credit for her discovery and subsequent work has been restored to Dr. Payne-Gaposchkin. She is also credited with establishing that stars can be classified by their temperatures, and published more than 150 papers on stellar atmospheres, stellar spectra. She also worked with her husband, Serge I. Gaposchkin, on variable stars. She published five books, and won a number of awards. She spent her entire research career at Harvard College Observatory, eventually becoming the first woman to chair a department at Harvard. Despite successes that would have gained male astronomers at the time incredible praise and honors, she faced gender discrimination throughout much of her life. Nonetheless, she is now celebrated as a brilliant and original thinker for her contributions that changed our understanding of how stars work.   As one of the first of a group of female astronomers at Harvard, Cecelia Payne-Gaposchkin blazed a trail for women in astronomy that many cite as their own inspiration to study the stars. In 2000, a special centenary celebration of her life and science at Harvard drew astronomers from around the world to discuss her life and findings and how they changed the face of astronomy. Largely due to her work and example, as well as the example of women who were inspired by her courage and intellect, the role of women in astronomy is slowly improving, as more select it as a profession.   A Portrait of the Scientist Throughout her Life Dr. Payne-Gaposchkin was born as Cecelia Helena Payne in England on May 10, 1900. She got interested in astronomy after hearing Sir Arthur Eddington describe his experiences on an eclipse expedition in 1919. She then studied astronomy, but because she was female, she was refused a degree from Cambridge. She left England for the United States, where she studied astronomy and got her PhD from Radcliffe College (which is now a part of Harvard University).   After she received her doctorate, Dr. Payne went on to study a number of different types of stars, particularly the very brightest high luminosity stars.  Her main interest was to understand the stellar structure of the Milky Way, and she ultimately studied variable stars in our galaxy and the nearby Magellanic Clouds. Her data played a large role in determining the ways that stars are born, live, and die.   Cecelia Payne married fellow astronomer Serge Gaposchkin in 1934 and they worked together on variable stars and other targets throughout their lives. They had three children. Dr. Payne-Gaposchkin continued teaching at Harvard until 1966, and continued her research into stars with the Smithsonian Astrophysical Observatory (headquartered at Harvards Center for Astrophysics. She died in 1979.