ASTRO 101 EXAM 2. QUESTIONS WITH 100% VERIFIED ANSWERS.

Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring? -Studying how a star's brightness varies over a period of 3 years. -Measuring the rotation rate of a distant star. -Studying how different planets differ in their surface compositions. -Determining the age of the solar system. Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates? -The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping. -Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence. -Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations. -Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities. The stars in our sky twinkle in brightness and color because of ______. -the bubbling and boiling of gases on the surfaces of stars -turbulence in the Earth's atmosphere -rapid changes in the brightnesses and colors of stars caused by changes in their spectra -light pollution Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? -Stars do not twinkle when observed from space. -It never has to close because of cloudy skies. -It is closer to the stars. -It can observe infrared and ultraviolet light, as well as visible light. What are the two most important properties of a telescope? 1. Light Collecting Area: -Telescopes with a larger collecting area can gather a greater amount of light in a shorter time. 2. Angular Resolution: -Telescopes that are larger are capable of taking images with greater detail. The Chandra X-ray Observatory must operate in space because: -It was built by NASA. -X rays do not penetrate Earth's atmosphere. -X rays are too dangerous to be allowed on the ground. -X-ray telescopes require the use of grazing incidence mirrors. The best ground-based sites for astronomical observing are: -Calm (not too windy) -High (Less atmosphere to see through) -Dark (Far from city lights) -Dry (Few cloudy nights) Which of the following telescopes benefits most from adaptive optics? -The Keck I telescope on Mauna Kea -The Hubble Space telescope -The Chandra X-ray Observatory -The Arecibo radio telescope in Puerto Rico Only ______ and ______ _________ pass easily through Earth's atmosphere. radio; visible light We need telescopes in space to observe other forms. Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.) -Observatory X can detect dimmer stars and Observatory Y reveals more detail in images. -Observatory Y can detect dimmer stars and Observatory X reveals more detail in images. -Observatory Y both detects dimmer stars and reveals more detail in images. -Both observatories have the same capabilities, but Observatory Y would be cheaper to build. -Observatory X both detects dimmer stars and reveals more detail in images. Interferometry A technique for linking two or more telescopes so that they have the angular resolution of a single large one. Easiest to do with radio telescopes -Now possible with infrared and visible-light telescopes Why can't X-ray and gamma-ray telescopes use the same designs as visible-light telescopes? -X rays and gamma rays are so intense that they would melt the glass in a visible-light telescope. -X rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light. -Visible-light telescopes can only reflect light that we see, not any other kind of light. -X rays and gamma rays do not penetrate Earth's atmosphere. Sort each of the astronomical questions below into the appropriate bin based on the type of observation you would need to perform to answer it. Imaging: -How large is the Andromeda Galaxy? -Are stars in the Orion Nebula surrounded by dusty disks of gas? -What are the major surface features of Mars? Spectroscopy: -Is the star Vega moving forward us or away from us? -What is the temperature of Jupiter's atmosphere -What is the chemical composition of Crab Nebula? Timing: -Is the X-ray emission from the galactic center steady or changing? -Does the star Mira vary in brightness?