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28 Cards in this Set
- Front
- Back
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Hubble's Law shows the _________ at which ________ are __________ from the Earth.
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Hubble's Law shows the velocity at which celestial bodies are receding from the Earth.
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In the formula for Hubble's Law: V = H₀D; what does each variable equal?
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V=velocity of recession; measured in km/second
H₀=Hubble's constant at the time of observation in history of the universe D=distance;measured in Mpc (megaparsecs) |
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What is the name of this equation and what is its purpose?
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The Drake Equation; it is used to estimate the number of planetsthat might have beings with the ability to communicate with us.
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What is a globular cluster?
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Globular clusters are gravitationally bound groups of thousands (sometimes a million) of stars. They consist primarily of very old stars. Globular clusters are randomly distributed throughout the halo.
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What is an open cluster?
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Open clusters are loose aggregations of dozens or hundreds of young stars. They are generally not gravitationally bound and will disperse in a relatively short period of time, astronomically speaking.
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Where would you find nebulas in a spiral galaxy?
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In the spiral arms.
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What are the most distant objects we know of in space called?
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quasars
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What is a spinning neutron star called?
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a pulsar
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What is a binary star?
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Two stars closely orbiting one another
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What is a chromatic abberation?
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Lens focuses different wavelengths of light differently causing blurs
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Refracting telescopes are limited by ___________.
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The size of the objective lens. If a lens is too large, the image begins to distort as the glass sags under its own weight.
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A __________ telescope uses a curved mirror to collect light.
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reflecting
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What is an ecliptic?
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path sun travels in one year
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What is the atmosphere on Earth currently made up of?
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Oxygen and nitrogen
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What is the zenith?
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The point directly overhead in the sky.
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What is the nadir?
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The point on the bottom of the sky directly under your feet.
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How does an Angstrom convert into meters?
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1 Angstrom=10E-10 meters
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What is the range of visible light (Angstroms)?
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between 4000 Å and 7000 Å
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How many nanometers in a meter?
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10E-9
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beyond the _____ end of the visible spectrum lies infrared radiation
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red
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What is an atmospheric window?
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A wavelength region where Earth's atmosphere is transparent----- visual, infrared and radio wavelengths.
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What is focal length?
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the distance from the lens or mirror to the image formed of a distant light source such as a star.
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True or False: Achromatic lenses are always free of chromatic aberration.
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False, other wavelengths blur besides blue wavelengths.
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True or False: Reflecting Telescopes are not only cheaper, but also are always free of chromatic aberration.
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True, the light is reflected from a metallic film on the front surface of the mirror and never enters the glass.
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What is resolving power?
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The ability of a telescope to reveal fine detail.
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What is a diffraction fringe?
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a blurred fringe surrounding any image ;caused by the wave properties of light; because of this, no image smaller than the fringe can be seen.
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What are active optics?
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computer-driven thrusters found under either a floppy-type mirror segmented-type mirror
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