Assignment #12

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Case Western Reserve University *

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406

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Astronomy

Date

Dec 6, 2023

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docx

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Uploaded by lxc386

Assignment #12 (1) Pluto (5 pts.) Why don’t astronomers consider Pluto to be a major planet anymore? Write a paragraph giving a careful and thorough scientific explanation. There are several reasons for astronomers do not consider Pluto to be a major planet anymore. First, Pluto is too small to be included, it is much smaller than other major planets. Second, even Pluto is as dense and rocky as some other major planet in solar system, the planets that Pluto is closest to are gaseous, which indicate that Pluto formed other place in the galaxy rather than solar system, it was captured or caught by the Sun’s gravity. Third, the orbit of Pluto is 17-degree angle compared to its plane, while other major planets have relatively flat orbital plane. Last, among the moons of Pluto, one moon is about half the size of Pluto, which makes astronomers consider these two as a binary system rather than planet and satellite system in solar system. (2) The Atmosphere of Mars (6 pts.) Today, the planet Mars is about 1.5 AU from the Sun, while Venus is 0.72 AU from the Sun. Suppose that instead, 4.6 billion years ago, Mars had formed at 0.72 AU from the Sun, but was in every other way unchanged. How would you expect the atmosphere of Mars to be today in terms of quantity and chemical composition? (Obviously it would be warmer.) Please choose one of the three options below, and then write a thorough and detailed defense of your response. a) The atmosphere of Mars would be similar to how the atmosphere of Mars is today. b) The atmosphere of Mars would be similar to how the atmosphere of Venus is today. c) The atmosphere of Mars would be very different from either how Mars or Venus are today.

I would expect the atmosphere of Mars would be very different from either how Mars or Venus is today (Option c). If the Mars had formed at 0.72 AU from the Sun, it would lose its atmosphere quickly because its weaker gravity can’t maintain the gases. I suppose the Mars would be a warmer planet which lacks atmosphere. (3) Cloud Bands (5 pts.) Astronomers discover a planet orbiting around another star. The star is very much like our Sun, and the planet is almost a twin to Jupiter. The planet has the same mass as Jupiter, is the same distance from its star as Jupiter is from our Sun (5.2 AU), has the same orbital period (12 years), is the same temperature, and has the same density and chemical composition as Jupiter. However, when we take a close up picture of the planet, we find that its clouds are not lined up in East/West bands like Jupiter. Instead the clouds appear to randomly swirl around. Propose a hypothesis to explain why this planet's clouds would not be organized into East/West bands like we see on Jupiter. The reason that the clouds in Jupiter are lined up in East/ West bands is resulted from the direction of wind on Jupiter. The direction the winds flow on Jupiter is in East/West direction, which push the clouds to move in the same direction. So, if the winds on this planet move in different directions, this can cause the clouds to appear to randomly swirl around. (4) Meteorite Ages (5 pts.) When meteorites fall to the earth, we can sometimes measure the ages by studying the amounts of different radioactive elements that they contain, in pieces called "calcium-aluminum-rich-inclusions". The oldest known meteorites are slightly less than 5 billion years old. Suppose that in the future, we use radiometric dating on a meteorite and find that it is 7 billion years old. To explain this unusually large age, someone proposes: "Perhaps this meteorite is from another galaxy." Evaluate this proposal. Does this hypothesis make sense? Write a few sentences explaining why or why not. If not, propose a similar but more reasonable hypothesis. This hypothesis doesn’t make sense. Since our galaxy is 13.6 billion years old. This meteorite may come from the same galaxy but different planetary

system (because our solar system is only 4.5 billion years old), for instance, Kuiper belt, where it should take very long time to get to the earth. (5) Time scale for the solar system. In this question we construct a scale model for the solar system, similar in principle to the scale models that can be found at most planetariums or science museums. Instead of scaling DISTANCE we are scaling TIME. The idea is to get a sense of relative times between important solar system events. Thus, we will create a scaled timeline of solar system events. Suppose we take an average American lifespan of about 80 years to be 1 centimeter in our timeline. This is the scale factor of our timeline. At one end of our timeline, we make a mark indicating now. (2 pts.) (a) Using our scale factor, how long ago was the town of Boulder founded? Let's use 1860, the year when the Wellman brothers planted the first wheat crop in Boulder County, and the year when the first schoolhouse in Colorado built strictly for educational purposes was erected in Boulder on the southwest corner of 14th and Front [Walnut]. In our model, how far from now were these events? 2022-1860=162 years. 162/80=2.025 cm (2 pt.) (b) If we guess that native americans were in Boulder about 10,000 years ago, how far from now is that in our scaled model? (For this and the following questions, please convert your answer to meters, kilometers, or whatever is the most appropriate metric unit of length.) 10000/80=125cm=1.25m=1.25*10 -3 km (2 pt.) (c) The Flatiron Mountains were formed about 40 million years ago. Find how far from now to place this in our scale model for time scales of the solar system. 40*1*10 6 /80=5*10 5 cm=5000m=5km (1 pt.) (d) Dinosaurs hung around Boulder about 120 million years ago - where do we put this event?

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