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Astronomy 1122: 2
Stars and Galaxies
| Question | Answer |
|---|---|
| Electromagnetic Radiation | Changing electric and magnetic fields that travel through space at the speed of light and transfer energy from one place to another; examples are light and radio waves |
| wavelength | the distance between successive peaks or troughs of a wave. |
| photon | a quantum of electromagnetic energy; carries an amount of energy that depends inversely on its wavelength. |
| nanometer | a unit of distance equaling one-billionth of a meter. used to measure wavelength of light. |
| angstrom | a unit of distance; used to measure wavelength of light. |
| atmospheric window | wavelength region in which our atmosphere is transparent- at visual, infrared, and radio wavelengths. |
| focal length | the focal length of a lens is the distance from the lens to the point where it focuses parallel rays of light. |
| primary lens or mirror | the largest lens or mirror in a telescope. |
| objective lens or mirror | in a refracting telescope, the long focal length lens that forms an image of the object viewed; the lens closest to the object. in a reflecting telescope, the principal mirror that forms an image of the object viewed. |
| eyepiece | a short-focal-length lens used to enlarge the image in a telescope; the lens nearest the eye. |
| refracting telescope | a telescope that from images by bending light with a lens |
| reflecting telescope | a telescope that uses a concave mirror to focus light into an image. |
| chromatic aberration | a distortion found in refraction telescopes because the lenses focus different colors at slightly different distances; images surrounded by color fringes. |
| achromatic lens | a telescope lens composed of two lenses ground from different kinds of glass and designed to bring two selected colors to the same focus and correct for chromatic aberration. |
| light gathering power | the ability of a telescope to collect light. |
| resolving power | the ability of a telescope to reveal fine detail. |
| diffraction fringe | blurred fringe surrounding any image, cause by the wave properties of light. |
| seeing | atmospheric conditions on a given night. |
| magnifying power | the ability of a telescope to make an image larger. |
| light pollution | the illumination of the night sky by wasted light from cities and outdoor lighting, which prevents the observation of faint objects. |
| prime focus | the point at which the objective mirror that forms an image in a reflecting telescope. |
| secondary mirror | in a reflecting telescope, a mirror that directs the light from the primary mirror to a focal position. |
| Cassegrain focus | the optical design in which the secondary mirror reflects light back down the tube through a hole in the center of the objective mirror. |
| Newtonian focus | the optical design in which a diagonal mirror reflects light out the side of the telescope tube for easier access. |
| Schmidt-Cassegrain focus | the optical design that uses a thin corrector plate at the entrance to the telescope tube. |
| sidereal drive | the motor and gears on a telescope that turn it westward to keep it pointed at a star. |
| equatorial mounting | a telescope that allows motion parallel to and perpendicular to the celestial equator. |
| polar axis | in an equatorial telescope mounting, the axis that is parallel to Earth's axis. |
| alt-azimuth mounting | a telescope mounting that allows the telescope to move in altitude(perpendicular to the horizon) and in azimuth (parallel to horizon). |
| active optics | thin telescope mirror that are controlled by computers to maintain proper shape as the telescope moves. |
| adaptive optics | a computer-controlled optical system used to partially correct for seeing in an astronomical telescope. |
| interferometry | the observing technique in which separated telescopes are combines to produce a virtual telescope with the resolution of a telescope much larger in diameter, |
| charge-couples device (CCD) | an electronic device consisting of a large array of light-sensitive elements used to record very faint images. |
| false-color image | a representation of graphical data with added or enhanced color to reveal detail |
| spectograph | a device that separates light by wavelengths to produce a spectrum- a fingerprint of the source producing light. |
| grating | a piece of material in which numerous microscopic parallel lines are scribed. light encountering a grating is dispersed to form a spectrum. |
| comparison spectrum | a spectrum of known spectral lines used to identify unknown wavelengths in an object's spectrum; helps identify fingerprint of spectrum. |
| radio interferometer | two or more radio telescopes that combine their signals to achieve the resolving power of a larger telescope. |
| One problem faced by astronomers is that only a small portion of ______ reaches Earth. | electromagnetic radation |
| One of the main problems of refractions telescopes in the inability to focus all colors of light simultaneously, which is known as _______ aberration. | chromatic |
| One of the principal advantages of _______ is that light does not pass through a significantly thick piece of glass. | reflecting telescopes |
| Astronomers overcome the relatively poor ______ power of a radio telescope by combining two or more such telescopes into a radio ______. | resolving, interferometer |
| What is the shortest wavelength between x-ray, radio waves, visible light, and ultraviolet light? | x-ray |
| The energy associated with an electromagnetic wave is inversely proportional to the wave's | frequency |
| In addition to visible light, earth's atmosphere is transparent to | radio waves |
| the 10 meter Keck telescope in Hawaii is the world's largest | segmented reflecting telescope |
| the newest, largest ground based optical telescopes are supported by | alt-azimuth mounting |
| for an optical telescope used on earth under normal seeing conditions, the main value of making larger telescopes is greater | light-gathering power |
| large, thin mirrors, sometimes called "floppy mirrors", sag under their own weight. to correct this, | computer controlled thruster are placed under the mirror to change the shape of the mirror several times per second. |
| earth's atmosphere causes the images seen in telescopes to be blurred. this can be corrected by a process known as | adaptive optics |
| the Hubble space telescope, orbiting above earth's atmosphere, eliminates the blurring effect of earth's atmosphere and permits the telescope to | observe wavelengths from the near infrared to the near ultraviolet. |
| sunspots | relatively dark spots on the sun that contain intense magnetic fields |
| granulation | the fine structure of bright grains covering the sun's surface. |
| convection | circulation in a fluid driven by heat. |
| filtergram | a photograph (usually in the sun) taken in the light of a specific region of the spectrum. |
| spicules | small, flamelike projections in the chromosphere of the sun. |
| supergranules | very large convective features in the sun's surface. |
| magnetic carpet | the network of small magnetic loops that covers the solar surface. |
| solar wind | rapidly moving atoms and ions that escape from the solar corona and blow outward through the solar system. |
| helioseismology | the study of the interior of the sun by the analysis of its modes of vibration. |
| Maunder butterfly diagram | a graph showing the latitude of sunspots versus time. |
| Zeeman effect | the splitting of spectral lines into multiple components when the atoms are in a magnetic field. |
| Maunder minimum | a period of less numerous sunspots and other solar activity between 1645 and 1715. |
| active regions | magnetic regions on the solar surface that include sunspots, prominences, flares, and similar features. |
| differential rotation | the rotation of a body in which different parts ot the body have different periods of rotation. |
| dynamo effect | the process by which a rotating, convecting body of conducting matter can generate a magnetic field. |
| Babock model | a model of the sun's magnetic cycle in which the differential rotation of the sun winds up and tangles the solar magnetic fiels in a 22 year cycle. |
| weak force | one of the four forces of nature; is responsible for some form of radioactive decay. |
| strong force | one of the four forces of nature; binds protons and neutrons together in atomic nuclei. |
| nuclear fission | reactions that break the nuclei of atoms in to fragments. |
| nuclear fusions | reactions that join the nuclei of atoms to form more massive nuclei |
| prominence | a looping eruption of the solar surface. |
| flares | violent eruptions on the sun's surface. |
| reconnection | one the sun, the merging of magnetic fields to release energy in the form of flares. |
| auroras | the glowing light displays that result when a planet's magnetic field guides charged particles so that they strike the upper atmosphere and excite atoms to emit photons. |
| coronal holes | areas of the solar surface that are dark at X-ray wavelengths; may be the source of solar wind. |
| coronal mass ejections (CMEs) | matter ejected from the sun's corona in powerful surges guided by magnetic fields. |
| Coulomb barrier | the electrostatic force of repulsion between bodies of like charge. |
| proton-proton chain | a series of three nuclear reactions that builds a helium atom by adding together protons. |
| deuterium | an isotope of hydrogen in which the nucleus contains one proton and one neutron. |
| neutrino | a neutral atomic particle that travels at or nearly at the speed of light. |
| the main mechanism for producing energy in the sun in nuclear | fusion |
| in the proton-proton chain, energy appears in the from of gamma rays, neutrinos, and | positrons |
| in the first reaction of the proton-proton chain, two protons combine to form a heavy hydrogen nucleus called | deuterium |
| an average sunspot is _______ the size of Earth. | twice |
| Ionized gas trapped in a magnetic field causes arched shapes that occur in the chromosphere called ________. | prominences |
| Energy in the solar wind guided by Earth's magnetic field excites gases in the upper atmosphere and produces __________. | auroras |
| what is the sequence of the layers of the solar atmosphere from the inside out? | Photosphere, chromosphere, corona |
| what is the sequence of the layers of the interior of the sun from the inside out. | core, radiative zone, convective zone |
| the babcock model explains the magnetic cycles as____________. | a progressive tangling of the solar magnetic field. |
| During the maunder minimum, europe and north america experiences a period of unusually _________. | cool weather |
| granules just below the photosphere are cause by what kind of heating? | Convective |
| When referring to the absorption lines in a spectrum, the photons of specific wavelengths are absorbed in the sun's what? | photospehere |
| astronomers use the Zeeman effect to measure what? | the strength of the magnetic field. |
| auroras are most frequent when? | at sunspot maximum |
| flares produce sudden eruptions of X rays and UV photons that reach Earth when? | in 8 minutes. |
| the sun rotates _____? | the slowest near the poles. |
| the four fundamental forces are | gravity, electromagnetic, weak nuclear, and strong nuclear. |
| solar nebula theory | the theory that the planets formed from the same cloud of gas and dust that formed the sun. |
| extrasolar planet | a planet orbiting a star other than the sun; also known as the exosolar planet. |
| asteroid | a small, rocky world. most asteroid lie between Mars and Jupiter in the asteroid belt. |
| comet | one of the small, icy bodies that orbit the sun and produce tails of gas and dust when the approach the sun. |
| terrestrial planet | an earthlike planer; small, dense, and rocky. |
| jovian planet | Jupiter-like planets with a large diameter and low density. |
| Galilean satellites | the four largest satellites of Jupiter, names after their discoverer. |
| meteor | a small but of matter heated by friction to incandescent vapor as it falls into Earth's atmosphere. Also refers to the flash of light seen in the sky. (shooting star) |
| meteorite | a piece of space debris that produces a meteor and survives its passage through the atmosphere and strikes the ground. |
| meteoroid | a meteor in space before it enters the Earth's atmosphere. the small piece of space debris. |
| half-life | the time required for half of the atoms in a radioactive sample to decay. |
| gravitational collapse | the process by which a forming body, such as a planet, gravitationally captures gas from its surroundings. |
| uncompressed density | the density that a planet would have if its gravity did not compress it. |
| condensation sequence | the sequence in which different materials condense from the solar nebula as we move outward from the sun. |
| planetesimal | one of the small bodies that formed from the solar nebula and eventually grew into protoplanets |
| condensation | the growth of a particle, atom by atom, by addition of material from surrounding gas. |
| accretion | the sticking together of solid particles to produce a larger particle |
| protoplanet | massive object resulting from the coalescence of planetesimals in the solar nebula and destined to become a planet. |
| differentiation | the separation of planetary material according to density. |
| outgassing | the release of gasses from a planet's interior. |
| heat of formation | in planetology, the heat released by infalling matter during the formation of a planetary body. |
| radiation pressure | the force exerted on the surface of a body by its absorption of light. small particles floating in the solar system can be blown outward by the pressure of the sunlight. |
| heavy bombardment | the intense cratering during the first 0.5 billion years in the history of the solar system. |
| snowline | the demarcation point between the inner and outer regions of our solar system where temperatures are low enough for water to condense out of the solar nebula and form what are snowflakes. these snowflakes stick to rocky, rapid growth large planets |
| Kupier belt | the collection of icy planetesimals believed to orbit in a region from just beyond Neptune out to 100 AU or more. |
| Oort cloud | the hypothetical source of comets. A swarm of icy bodies believed to lie in a spherical shell extending to 100,000 AU from the sun. |
| The adding of material an atom at a time is the process of ___________. | condensation |
| The ______ model is used to describe the physical structure of ________. | dirty snowball, comets |
| The pressure of sunlight was one of the forces that cleared out the _________. | solar nebula |
| the ______ planets have lower average densities than the _______ planets. | Jovian, terrestrial |
| Planets begin to form when _______ join to make larger objects called ________. | planetesimals, protoplanets |
| Evidence of cratering on the moon and other terrestrial planets suggests that Earth what? | experience a similar kind of cratering earlier in its history. |
| Because of Earth's low mass, our planet's atmosphere contains what? | contains very little hydrogen and helium. |
| The orbits of the planets | all lie in approximately the same plane |
| Each of the planets in our solar system orbits the sun | in the same direction, counterclockwise as seen from above (north). |
| The orbits of the planets lie mainly in the same plane because the planets | formed from a large thin disk of material surrounding the new sun. |
| The solar system has relatively little gas and dust between the planets. The lack of this material is probably the result of what? | radiation pressure from the sun |
| The solar nebula theory describes how the planets formed from | a disk shaped cloud of gas and dust around the newly forming sun. |
| The terrestrial planets nearest the sun are | small, solid, and rocky. |
| The atmospheres of the Jovian planets are made primarily of | hydrogen and helium. |
| Most asteroid revolve around the sun between the orbits of | Mars and Jupiter. |
| Objects made mostly of ice that form a large gaseous "tail" that is directed away from the sun at all times are called | comets. |
| Formation of planetesimals by condensation refers to the process of | matter building one atom at a time. |
| Solid particles sticking together to form larger particles describes the process of | accretion |
| The separate of low density and high density materials in a planet during the early stages of its formation is referred to as | differentiation. |
| The interiors of Jupiter and Saturn consist mostly of | liquid hydrogen |
| Low density and cold dust disks have been found around many stars. These disks are believed to be regions where planets have been formed or are in the process of forming. The disks are most readily detected by | infrared telescopes. |
| A planet that has formed around the star 51 Pegasi has been detected by | Doppler shifts in the star's spectrum as the planet orbits, causing the star to wobble back and forth. |
| The source of comets is | the Kuiper belt and the Oort cloud. |
| Our solar system may have a cold dust disk similar to that found around the star Beta Pictoris. Astronomers believe that this disk is located in the ________ of objects. | Kuiper belt. |
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