Astronomy 150 - Exam #2 Name:May 21, 1999 TA’s Name & Section:Answer all questions in the space provided. If you have any questions, raise yourhand. 100 points possible.1 (6 pts) Meteorites are just as likely to fall in Western Washington as anywhere else onthe Earth. However, if we were to search around Western Washington we would be muchless likely to find a meteorite than if we searched the same amount of land in the Australiandesert. Explain why this is. [2 reasons]2 (6 pts) Even if we had a “piece” of the Sun we could not determine its age (it would justbe a handful of gas). So, how do we know the Sun is 4.5 billion years old?3 (4 pts) How do we know that comets did not form in the inner solar system?4 (6 pts) The Earth has only a few impact craters visible on its surface. Yet we believethat in the past the Earth was bombarded by impactors. Why do we believe the Earth washeavily bombarded in the past?5 (5 pts) To the left is an image of an impact crateron the icy surface of Europa. The impact crater hasa diameter of 26 kilometers. If we assume that thedark material came from underneath the ice, whatis the maximum thickness the ice can have? [showyour work]6 (6 pts) The Earth’s Moon and Saturn’s moon Titan are about the same size and haveabout the same gravity. Titan has a thick atmosphere while the Moon has none. Explainwhy this is.SUN123 AU330 AU47 (8 pts) The four numbered circles in the diagram above represent the locations but NOTthe sizes of four different solid worlds in our Solar system. Assume that each of thoseworlds formed from materials at their indicated locations. Describe the approximate bulkcomposition and density of each of the worlds.8 (8 pts) Answer the same question as above but assume that the system formed around astar twice as hot as the Sun.You have discovered three airless moons around anotherplanet. The planet has a radius of 10,000 km and a massabout the same as Jupiter’s. You determine the distance fromthe planet and the period for each moon (table on right).Based onlyon this data answer the next three questions:Name Distance Period(km) (hours)A 20,000 0.4B 100,000 5.0C 160,000 10.09 (6 pts) Which of the moons would you deduce is the small-est moon? (check one) A B CExplain your reasoning:10 (6 pts) Which of the moons would you deduce is beingtidally heated? (check one) A B CExplain your reasoning:11 (6 pts) Which of the moons would you deduce is the mostcratered? (check one) A B CExplain your reasoning:12 (10 pts) One of the moons in the system from the previous page is being tidally heated.Describe how tidal heating works and draw a diagram using this system as an example.13 (5 pts) Explain why the other moons in the system are not tidally heated.1.00.80.60.40.20.0RedBlue Green Yellow Orange InfraredABReflectanceWavelengthCFrom the Earth you measure the re-flectance spectra of the three moons(A, B, and C) in the system (seegraph on left). Use these spectra toanswer the remaining questions.14 (9 pts) Describe the colors and relative brightnesses of the moons if you were to observethem visually.15 (3 pts) Describe the relative brightnesses of the moons if you observed them in theinfrared.16 (6 pts) Speculate what materials might make up the surfaces of each of the
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