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Astronomy/physics
Multiple choice
| Question | Answer |
|---|---|
| Why are we able to see only a small part of our galaxy, the milky way galaxy? | distant stars are obscured by dust and gas in interstellar space. |
| the dimensions of the disk of our milky way galaxy are | diameter 160,00 light-years; thickness, 200 light-years |
| radio waves of 21-cm wavelength originate from which component of the interstellar medium? | neutral atomic hydrogen |
| which type of radiation has been most effective in evaluating the spiral structure of our galaxy? | 21-cm radio emission from the "spin-flip" transitions in cool hydrogen gas |
| the milky way galaxy appears to have a spiral structure with | at least four separate major arms. |
| the time taken for the sun to orbit the galactic center once in its motion in the galaxy is | 220 million years |
| much of the mass of our galaxy appears to be in the form of "dark matter" of unknown composition. At present this matter can be detected only because | its gravitational pull affects orbital motions of matter in the galaxy |
| what fraction of the mass of our galaxy appears to be in the form of dark matter, which we cannot see but detect through its gravitational influence? | about 90% |
| the possible presence of a supermassive black hole at the center of our galaxy has been deduced from | the very high orbital speed of stars close to the galactic center. |
| what appear to be the characteristics of the object at the center of our galaxy? | three million solar masses in a volume the size of our solar system. |
| the number of degrees in a full circle is | 360 |
| one astronomical unit, or one AU is defined as the | mean distance between the sun and earth |
| One Light-Year is the | distance that light travels in one year |
| The star (puppies is about 750pc from earth. expressed in light years, this is approximately | 2445 ly |
| radio waves travel through space at what speed? | at the speed of light, 3*10^8 m/s |
| around 1800 William Herschel passed light through a prism and discovered that part of non-visible radiation in the resulting spectrum would raise the temperature of a thermometer. this portion of the electromagnetic spectrum is | infrared |
| what takes up only a very small part of the total range of wavelength in the electromagnetic spectrum. | visible light |
| Earths Atmosphere is transparent to which of the following types of electromagnetic radiation? | radio waves |
| in the 1790s Sir William Herschel tried to measure the Suns position in our galaxy by | counting the density od stars in different directions along the Milky Way. |
| the unknown factor that mislead Herschel into concluding that the stars of the Milky Way were distributed with the Sun at the center of the galaxy was | the presence of significant interstellar dust, which obscured the more distant stars and thereby localized his observations. |
| the idea that some of the "nebulae" that are observed in the sky might be "island universes"=immense collections of stars far beyond the Milky Way- was first proposed by | Immanuel Kant in 1755 |
| the event that eventually settled the Shapley-Curtis debate about "spiral nebulae" was | Edwin Hubble measuring the distance to the Andromeda galaxy. |
| it is the year 1920 and yur are conducting a survey of the astronomy community on the question: " what is the nature of the spiral nebulae?" what response are you likely to receive? | the overwhelming opinion is that spiral nebulae are relatively small objects in the outer part of the milky way galaxy. |
| the observation by Hubble that demonstrated for the first time that Andromeda nebulae was at a very large distance from the sun, and outside our galaxy, was | that Cepheid variable stars appeared to be very faint in "nebula". |
| the significant feature of a Cepheid variable is that there is a relationship between two intrinsic parameters, the first being easily measured, the second being the parameter that is required. these parameters are | period of brightness variation and luminosity. |
| who developed the classification system that divides galaxies into spiral, elliptical, and irregular, and classifies spirals by the size of their nuclear region and the tightness of winding of their arms | Edwin hubble |
| what is the basic shape of a spiral galaxy? | a round, flat disk containing long lanes of stars that curve outward in a spiral shape from the edge of a round, nuclear region of uniform brightness. |
| the Hubble classification for a galaxy with a circular outline and a smooth distribution of brightness is | E7 |
| the Hubble classification for a spiral galaxy with a tiny central bulge and narrow, well-defined, loosely wound spiral arms is | E0 |
| THE TYPE OR GROUP OF GALAXIES THAT CONTAINS BOTH THE LARGEST AND SMALLEST GALAXIES IN THE UNIVERSE IS | THE ELLIPTICALS |
| the discovery that the sun and similar stars are about 25% helium posed a dilemma: there was too much helium in the universe to be accounted for by nucleosynthesis in stars in the contemporary cosmological models. How was this dilemma resolved? | the was universe found to be older than originally thought, thus allowing more time for stars. |
Created by:
dulceleguizamo