Test Natural Sciences 102 Section 8 Noon --- VERSION B March 30, 2007

Transcription

1 Correct responses shown in boldface. 1. Active galaxy nuclei are powered by a. matter falling into a very massive black hole b. lots of star formation c. energy left over from when the galaxy formed d. radio jets extending out into space e. galaxy mergers 2. A good way to look for a massive black hole in the nucleus of a galaxy is to look for a. a dark spot projected against the starlight of the galaxy b. a tight knot of stars being sucked into the gravitational field of the black hole c. lensing of background galaxies behind the nucleus d. distortions in the shape of the galaxy due to the large gravitational field e. very large Doppler shifts in the spectra of stars close to the center of the galaxy 3. The clearest evidence that quasars are at great distance is a. their small parallaxes b. that they lie in the centers of galaxies that are at large distances c. that their emission lines are broad d. that they vary rapidly e. the faintness of the Cepheid variables in them 4. The outer part of the rotation curve of a galaxy is flat; this fact indicates that a. practically all the mass of the galaxy is within the radius where the curve flattens out b. where the curve is flat, the encircled mass increases with increasing distance from the center c. Newton's law of gravity is wrong d. there is a supermassive black hole at the center of the galaxy e. the galaxy is still in the process of forming 5. Spiral arms are prominent in some galaxies because a. they mark where the dust is thin and we can see the stars better b. they show where young and bright stars have formed c. they represent bright blobs that have been wound into the spiral shape by the galaxy rotation d. Population III stars make them bright e. they mark where material has been ejected by the nucleus 6. Stars with high concentrations of elements heavier than hydrogen and helium a. are likely to be very old b. are found in globular clusters c. are likely to have formed relatively recently d. are members of population II e. have very low mass 7. What do we call the faint, roughly spherical, collection of old stars around the entire Milky Way? a. disk b. halo c. bulge d. spiral arms e. dark matter 8. The mass of a cluster of galaxies a. is entirely from its galaxy members b. includes a significant part from very hot gas and even more from dark matter c. results in broadening the spectral lines from active nuclei in the cluster d. causes the cluster to glow all over as things fall into it e. makes the emission lines of the galaxies in the cluster shift wavelength significantly due to relativity 9. The large-scale distribution of the galaxies in space is a result of a. the structure of the early Universe b. galaxies of similar types tending to clump together c. the gravitational attraction of great black holes that attract galaxies to their vicinity d. that galaxies tend to slow each other down when they pass closely, making them tend to concentrate together e. galaxies are fairly uniformly distributed, but intergalactic dust clouds hide aome of them and make the distribution look clumpy 1

2 10. A newly formed massive, hot star changes the surrounding interstellar gas into a. a molecular cloud b. a glowing cloud of excited gas called an HII region c. a dark globule seen as a shadow against the background light d. an HI region e. interstellar dust 11. Interstellar dust makes the things behind it look a. bluer and fainter b. greener and brighter c. redder and more diffuse d. it blots them out completely e. redder and fainter 12. A "reflection nebula" is a. a cloud of interstellar grains aligned to reflect light similarly to a mirror b. a nebula that has symmetry along a central line that makes it look like it is reflected in a mirror c. a cloud of interstellar material that lets look into regions we cannot see directly d. an interstellar cloud that absorbs energy from nearby stars and emits it in the infrared e. an interstellar cloud that is lit up by scattering light toward us from a star near the cloud 13. The Shapley-Curtis debate a. was important philosophically because the topics touched on our place in the Universe b. was decisively won by Shapley c. was decisively won by Curtis d. was an argument about the role of star formation in affecting our view of the cosmos e. had to do with the superiority of Harvard College Observatory 14. A "standard candle" for an astronomer is a. a special candle of constant brightness maintained at the Bureau of Standards b. an astronomical object whose luminosity can be determined independent of knowing its distance c. a barred spiral galaxy d. a votive candle of the usual size and wax content e. a variable red supergiant star 15. When we look at a galaxy that is 10 million light years away, the light we see a. was created 10 million years ago, before there were humans b. is as it was 10 million light-years ago c. has dimmed by 10 million times in reaching us d. will be spread over the next 10 million years e. looks the same as it would have 10 million years ago 16. You are given a very long exposure ( deep image ) of the sky taken with the Hubble Space Telescope. You count the number of galaxies regardless of brightness in a small area on the image, and you report that there are 100 galaxies. How uncertain is your number? a. there is no uncertainty any similar sized area will have 100 galaxies b. the uncertainty for similar areas is 10 galaxies due to counting statistics c. the uncertainty cannot be estimated without knowing the large scale structure in this direction d. the uncertainty is proportional to the brightness of the galaxies e. the statistical uncertainty depends on the types of the galaxies 17. We believe the Milky Way is a spiral galaxy because a. we see the spiral arms reflected in dust clouds in the halo b. from the way the stars rotate around the center c. radio observations of interstellar clouds show them to lie in arms d. X-ray data show that the red giants are bunched into a spiral pattern e. None of the above 2

3 18. Which of the following would you NOT expect to find in the halo of a galaxy a. M dwarfs b. Globular clusters c. Dark matter d. White dwarfs e. Massive O and B stars 19. Most elliptical galaxies have few young stars because a. the star forming regions were torn from them in collisions with other galaxies b. their large gravitational fields disrupt forming stars c. they have little interstellar gas d. there is too much dark matter and it interferes with star formation e. actually, ellipticals have more young stars than spirals and irregulars do 20. When a black hole is a bright source, such as an active galactic nucleus, it is because a. the event horizon is being broken to let the energy out b. material rotating rapidly outside the event horizon gets very hot and glows c. gravitational lensing concentrates the energy from objects behind the black hole d. the jet from the black hole points right at us e. energy is streaming through the black hole from another Universe 21. When astronomers report that a source seems to be moving faster than the speed of light a. it can be the result of an optical illusion caused by sources moving nearly at the speed of light b. we consider it to be evidence that Einstein s theories are wrong c. the observations must be incorrect d. it is all on account of the Doppler shift e. nothing has been seen that appears to move faster than light this is all a hoax! 22. To avoid plagiarism, you should a. be careful to give credit for the sources of information you use b. change a few words in any long passage you copy into a paper c. don t list the source of a quotation in the references for a paper d. only use information that is in the public domain e. only get information from the internet 23. Books in the library are safe sources of good information because a. their publishers have the material carefully reviewed b. libraries only buy books they have determined are accurate c. to get a book published, an author must have a good reputation for accuracy d. books can in fact have a lot of wrong information e. the Library of Congress reviews books for false information 24. Henrietta Leavitt's period luminosity relation for RR Lyrae stars proved important because: a. it allowed the astronomers of her time to test their models for the interiors of these stars, to see if they were made of hydrogen b. it was the first significant astronomical discovery by a woman c. it explained why some star fields looked different in pictures taken at different times d. it allowed the luminosity of these stars to be determined based on intrinsic properties, and thus their distances from their apparent brightnesses e. it showed that they moved on the HR diagram 25. Distance measurements to the galaxies around us show that a. the Milky Way is isolated in space b. the Milky Way belongs to a group of only three galaxies, including M31 and M33 c. the Milky Way is part of a galaxy group in which it and M31 are surrounded by many small galaxies d. we are moving rapidly toward a certain point in space, leaving the nearby galaxies behind e. the Milky Way is orbiting M31, and we see its projected position move relative to background galaxies 3

4 26. Our own galaxy a. is "safe" from colliding with other galaxies for the foreseeable future b. is pulling apart some nearby galaxies and will eventually consume them c. is being pulled apart by the Andromeda Galaxy d. is highly distorted due to a very recent collision with a large galaxy e. we cannot tell if it is undergoing a collision with a galaxy because of the obscuration by interstellar dust 27. Galaxies can merge when a. They fall into a black hole b. They collide with each other and their stars combine into binaries c. They collide and much of their kinetic energy is transferred to stars that are thrown out into space d. Their interstellar clouds join together to make a new galaxy e. One of them accretes another. 28. Star formation a. occurs equally at all places in the disks of spiral galaxies b. tends to be enhanced where peaks in the local density compress the molecular clouds c. occurs wherever there is atomic hydrogen d. occurs where halo stars collide with the disk e. occurs in formations that spread into spiral arms due to the flat rotation curves of these galaxies 29. Which physical force dominates the process of star formation? a. strong nuclear b. weak nuclear c. electrical d. gravitational e. reactional 30. To form a real star, an object must be massive enough to a. have enough gravity to hold planets in orbit b. make an HII region c. explode as a supernova d. create enough pressure and heat in its core for hydrogen fusion e. burn hydrogen and helium into heavier elements 31. A very large clump of interstellar matter a. tends to become unstable and fragment or to lose matter through winds, rather than becoming a stable super-massive star b. can make a star up to nearly any mass range c. takes an extra-strong initial event to start it collapsing d. collapses into a star particularly slowly because it is so big e. can explode as a supernova rather than becoming a star 32. Because of the temperatures in the protoplanetary disk, a. rocks, metals, and ices (hydrogen compounds) froze in the inner region only b. rocks and metals froze in both the inner and outer regions, and ices froze only in the outer region c. rocks and metals froze in the inner region only, and ices froze in the outer region only d. rocks and metals froze in both the inner and outer regions, and ices and H and He gases froze only in the outer region 33. You are sent to find dense and rocky planets. Where in the Solar System should you look? a. very far from the sun b. only in the middle c. close to the sun d. in circular orbits e. in regions with lots of moons 34. A key characteristic of the cloud from which the Solar System formed was its a. rotation b. color c. age d. shape e. ability to have chemical reactions 4

5 35. The Galactic Center was hidden from astronomers for many years because a. it only emits in the radio and infrared b. it is a very diffuse region that is hard to pinpoint c. there were looking in the wrong places d. the Milky Way has a peculiar, atypical structure that made it hard to find e. it is hidden in the visible by clouds of interstellar dust 36. Most of the mass of the Milky Way is a. in its stars b. in the supermassive black hole in its center c. in the interstellar gas d. in a.) through c.) e. in the form of dark matter 37. Galaxies come a. in a chaotic, bewildering variety of shapes b. always in the same shape - but they look different to us because we view them at different angles c. in a limited number of shapes that we can describe in systematic ways d. in different shapes depending on what kind of material makes them up e. in different shapes depending on whether they have an active nucleus 38. We study galaxies at very high redshift to a. see how far away we can see b. determine how galaxies form and evolve to ones like ours c. look for active nuclei d. to see them smash into each other e. to probe the earliest stages in the evolution of the Universe 39. When matter falls into a black hole a. it quickly disappears from sight b. great amounts of energy can be released c. it passes out into another Universe d. it takes an unfamiliar form e. its light shifts to the blue 40. Superluminal - faster than light - motions result when a. the geometry of motions sets up an optical illusion b. matter falls into a black hole c. there is such a violent explosion that pieces are expelled faster than light d. Einstein's laws are broken e. neutrinos are accelerated to a very high speed 41. In very deep images that let us detect very distant and hence young galaxies, we find them to be a. very similar to nearby ones b. generally to be smaller and with less regular structure compared with nearby ones c. mostly to be ellipticals since bulges formed first d. all very obscured by the dust in their interstellar matter e. we cannot get a good enough sense of their nature to describe them well 42. What type of galaxy is shown in the picture at left? a. barred spiral b. Milky Way c. elliptical d. irregular e. spiral 43. What technical breakthough was revolutionizing astronomy 100 years ago? a. invention of the telescope b. the first mechanical calculators c. photography began to be used in astronomy d. accurate micrometers were introduced to measure double stars e. radio astronomy became widely applied 5

6 44. In the early 1900's it became possible to measure large numbers of RR Lyrae and Cepheid variables in the nearest galaxies because a. telescopes were built larger than ever before b. telescopes were put at high mountain sites for the first time c. the first observatories were built in the southern hemisphere d. photographic plates were used, so thousands of stars could be measured to very faint levels all together e. the first electronic detectors were introduced 45. Planetary systems form a. within the dense disks of material surrounding very young stars b. when young stars capture smaller bodies that formed near them c. in near-collisions of young stars that pull matter out of them d. in eruptions of material from stars settling onto the main sequence e. from convection cells in jets from young stars 46. When clumps first collapse into young stars, a. they cannot burn hydrogen because it has not settled into their cores yet b. they cannot burn hydrogen until a spark ignites it c. their activity level needs to rise before they can burn hydrogen d. their cores must shrink and heat up to burn hydrogen e. the hydrogen must be converted from molecular to atoms form to burn 47. The question of whether the spiral nebulae were galaxies like the Milky Way was settled a. when Heber Curtis decisively defeated Harlow Shapley in this part of their debate b. when Shapley showed how big the Milky Way is, using globular clusters c. when Edwin Hubble used the new 100-Inch Telescope to photograph stars in nearby galaxies d. by Herschel when he cataloged other galaxies in the process of mapping the sky e. when Henrietta Leavitt discovered the period-luminosity relation 48. It is important to study the center of the Milky Way because a. it gives infrared and radio astronomers something to do b. it helps us locate the position of the solar system within the galaxy c. there is a unique type of star there d. it gives a unique perspective on how a galaxy nucleus works e. actually, there is nothing of much interest there 49. Molecular clouds are mostly composed of a. ammonia and methane b. dust c. atomic hydrogen d. molecular helium e. molecular hydrogen 50. If we wait a long time, the Local Group of galaxies will look a. basically the same as now b. different because the large galaxies will have "eaten" some of the smaller ones c. different because all the galaxies will have turned to spirals d. like it has vanished because it will have dissipated into intergalactic space e. full of small galaxies because collisions will break up the large ones 6