A Sense of Where We AreOutlineReview QuestionsAnswersA Sense of Where We AreOutline1. Sizes of Some Astronomical ThingsA. Earth Diameter: 7900 miB. Earth-Moon Distance: 240,000 miC. Solar Diameter: 865,000 miD. Jupiter Diameter: 89,000 mi; Pluto diameter: 1440 miE. Earth’s Orbit Radius: 93 million miles = 150 million km  1 AUF. Pluto’s Orbit Diameter: 100 AUG. Oort Cloud Radius: 100,000 AUH. Distance to Proxima Centauri: 4.2 light yearsI. Milky Way Galaxy Diameter: 100,000 lyJ. Local Group Diameter: 3 million lyK. Local SuperclusterL. The Cosmic Address: Earth, Solar System, etc . . .2. ModelsA. Modeler’s Equation2Object of nceSize/Dista Model1Object of nceSize/Dista Model 2Object of nceSize/Dista Real1Object of nceSize/Dista RealB. Earth/Moon ModelC. Earth/Sun ModelD. Sun/Pluto ModelE. Sun/Proxima Centauri Model3. Events in the Life of the UniverseA. Big BangB. Galaxy FormationC. Star FormationD. Planet FormationE. Appearance of Life4. Carl Sagan’s Cosmic CalendarReview Questions1. Which is larger in size: the Solar Neighborhood or the Local Group?2. What is the astronomical unit (AU)? How is it related to the light year? (i.e., much larger, much smaller, about the same) How do you know?3. Match a description on the left with a distance/size on the right:____ possible distance of a planet orbiting the sun a) 10 light years____ distance to stars nearest to the sun b) 10 AU____ distance to galaxies nearest to the Milky Way c) 10 billion light years____ distance to very distant galaxies d) 1 million miles____ diameter of the sun e) 100,000 light years____ diameter of the galaxy we inhabit f) 1 million light years4. Where is the true boundary of the solar system?5. You board a spaceship and zoom off to a point 10,000 AU from the Sun, in a direction toward Proxima Centauri. Relative to these two stars, where are you?a) Much closer to the Sun than to Prox Cen.b) Much closer to Prox Cen than to the Sun.c) About midway between the Sun and Prox Cen.6. Ques. #2, pg. 25.7. Ques. #5, pg. 258. What is the ratio of the diameter of Jupiter to the diameter of Earth? (See pg A-11 in your text for planetary data). Using this ratio, find the diameter of a model. Earth if Jupiter is modeled as a large beach ball (diameter = 2.0 ft).9. Given the mean distance between the sun and Jupiter (pg. A-11), what is the scale distance between the sun and the beach ball Jupiter?10. Using a smaller beach ball to represent Jupiter would have what effect on your answer to #9?11. Ques. #10, pg. 26.Answers1. The Local Group is (much) larger. Local group is the small cluster of nearby galaxies which includes the Milky Way as a member. It’s about 3 million light years across. The Solar Neighborhood is the collection of stars near the Sun, comprising a patch of space ~15 light years across.2. The Astronomical Unit (AU) is the average distance between Earth and the Sun., and is much smaller than the light year. How do you know? Well, you could look it up! Or, remember the model we discussed in class: When the Sun is reduced to a nerf ball 10 cm across, Pluto, at 40 AU, lies about 0.25 mile from the ball, and the next nearest star (at 4 light years from the Sun) is found about 1800 miles from the ball. So, in the model, an AU is evidently scaled to 0.25/40 mi = 0.0063 mi, and a light year is evidently scaled to 1800/4 = 450 miles. Now, 450 miles >>> 0.0063 mi, so in reality a light year is evidently much bigger than an AU!3. Match a description on the left with a distance/size on the right:b) possible distance of a planet orbiting the sun a) 10 light yearsa) distance to stars nearest to the sun b) 10 AUf) distance to galaxies nearest to the Milky Way c) 10 billion light yearsc) distance to very distant galaxies d) 1 million milesd) diameter of the sun e) 100,000 light yearse) diameter of the galaxy we inhabit f) 1 million light years4. In the view of your instructor, the outer edge of the solar system is coincident with the outer edge ofthe Oort comet cloud – about 100,000 AU from the Sun. Oort cloud comets are the most distant objects orbiting the Sun, so they must belong to the solar system.5. a) Much closer to the Sun than to Prox Cen: Prox Cen lies about 267,000 AU from the Sun. 10,000 AU << 267,000 AU, so you’ve got to be much less than ½ the distance from the Sun to Prox Cen.6. Earth, through Solar System, to the stars, Milky Way Galaxy, other galaxies, Local Group, other galaxy clusters, Local Supercluster, and finally to the Universe as a whole, in which galaxies and galaxy clusters appear to be arrayed along filaments.7. Light carries information about the Universe. Light travels at a finite speed, so information about distant objects arrives at Earth only after a lapse of time. Thus, we see objects out there only as they were in the past, not as they are now. Light can have traveled from distant objects for a time interval no greater than the age of the Universe, which we believe to be about 13 billion years. So, the most distant objects we can see (at the edge of the observable Universe) must lie no more than about 13 billion light years from Earth.8. You need to solve the second equation below to solve this problem:Xft 2.0 km 12,800km 143,000Earth Model ofDiameter Jupiter Model ofDiameter Earth Real ofDiameter Jupiter Real ofDiameter In this case:inches 2.2 ft 0.18 ft 2.0 km 143,000km 12,800 X 9. You need to solve the second equation below to solve this problem:ft 2.0X km 143,000km 10 50.1DiameterJupiter ModelAU Model Jupiter Real ofDiameter AU Real8Solve for X: X = 2100 ft. So, if Jupiter is reduced to a 2.0-ft beach ball, then the AU is reduced to 2100 ft. Now, Jupiter lies 5.2 AU from the Sun, so in the model the distance between the Sun and Jupiter is:)(! miles 2.1 ft 11,000 ft/AU 2100 AU 5.2 10. A small Jupiter would of course result in a smaller AU. For example, a 1-ft Jupiter in the model would result in a model AU about 1 mile in length. (The sizes decline proportionately.)11. Well, the lifetime of the human race on Earth is pretty small compared to