Astronomy Chapter 18 Vocab – Flashcards
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cosmology
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the study of the Universe as a whole
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Olbers's paradox
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the observation that the sky is dark at night contrasted to a simple argument that shows that the sky should be uniformly bright
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Doppler shift
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the change in wavelength that arises from the Doppler effect, caused by relative motion toward or away from the observer
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Doppler effect
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a change in wavelength that results when a source of waves and the observer are moving relative to each other
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Allen Sandage
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the leader of measuring distances with Hubble
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Maarten Schmidt
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discovered quasars
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OGLE
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Optical Gravitational Lensing Experiement, a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side benefit
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Hubble's Law
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the linear relation between the speed of recession of a distant object and its current distance from us, v = H0d
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Hubble Space Telescope (HST)
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One of NASA's great observatories, a 2.4 telescope launched in 1990. It orbits a few hundred miles above Earth's surface, above most of the atmosphere, and has been uprgaded by space-shuttle astronauts several times. A very large number of studies have been conducted with it at ultraviolet, optical, and infrared wavelengths
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Hubble's constant
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The constant of proportionality in Hubble's law linking the speed of recession of a distant object and its current distance from us
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supernova
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the explosion of a star with the resulting release of tremendous amounts of radiation
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Type Ia supernova
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a supernova whose distribution in all types of galaxies, and the lack of hydrogen in its spectrum, make us think that its an event in low-mass stars, probably resulting from the incineration of a white dwarf in a binary system
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Type II supernova
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a supernova often associated with spiral arms, and that has hydrogen in its spectrum, making us think that its the explosion of a massive star
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core-collapse supernova
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a stellar explosion in which the iron core of a massive star collapses, forming a neutron star or a black hole, and the surrouding layers of gas are violently ejected
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how to detect a black hole
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look for a flickering x-ray, if you see a star there you can measure its Doppler shift, and the invisible object has to be more than 5x the mass of the Sun
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the Chandrasekhar limit
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the limit in mass, about 1.4 solar masses, above which electron degeneracy (a quantum-mechanical pressure) cannt support a star, and so the limit above which white dwarfs cannot exist
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light curve
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the graph of the brightness of an object vs. time
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homogenous
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uniform throughout
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isotropic
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being the same in all directions
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cosmological constant
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a constant arbitrarily added by Einstein to an equation in his general theory of relativity in order to provide a solution in which the Universe did not expand or contract
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WMAP
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Wilkinson Microwave Anisotropy Probe, shows that about 15% of the matter of the Universe contains protons, neutrons and electrons
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JWT
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James Webb Telescope, will be launched in 2018 and will see cool things in the infrared like exoplanets. Astronomers are petitioning to get it launched sooner
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positve curvature of space
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greater than 180°
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saddle curvature of space
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less than 180°
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Brian Smith
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surveyed for many different sueprnovae --> the Hein Z Supernova Project
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dark energy
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a generic name for the gravitationally repulsive energy that is thought by many to be the cause of the observed acceleration of the expansion rate of the Universe
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Lamant and Dike
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foudn that there are particles within particles
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Fermi lab
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biggest "atom smasher", located outside of Chicago
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CERN
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An acronym for French words meaning European Center for Nuclear Research, an example of an atom smasher
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ALICE
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A Large Ion Collider Experiment that tests the idea that quarks and gluons were once freely interacting in such a plasma instead of being trapped in composite particles as they are today
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Lepton
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any of a group of elementary particles and their antiparticles, such as an electron, muon, or neutrino, that participate in electromagnetic and weak interactions and have a half-integral spin
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Neutrino
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a spinning, neutral elementary particle with little rest mass ,formed in certain radioactive decays
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Quark
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one of the subatomic particles of which modern theoreticians believe such elementary particles as protons and neutrons are composed. The various kinds of these things have positive or negative charges of 1/3 e or 2/3e, where e is the unit of electric charge
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Higgs Boson
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(or Higgs particle) is an elementary particle in the Standard Model of particle physics
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Guth
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theorized than the universe was flat b/c it as inflated
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Fred Hoyle
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worked out the little detailsl that allows carbon to form
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the anthropic principle
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says that we exist, so therefore the Universe must have certain properties that allow us to be here
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deterium
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an isotope of hydrogen that has 1 proton and 1 neutron, and its abundance has enabled us to tell something about the mass of the early universe
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redshift
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a shift of optical wavelengths toward the red, or in all cases toward longer wavelengths
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Hubble diagram
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the plot of redshift (or recession speed) versus distance, graphically representing Hubble's law
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the big-bang theory
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a cosmological model, based on Einstein's general theory of relativity, in which the Universe was once extremely hot and dense, and has been expanding ever since
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Hubble time
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the amount of time since the big bang, assuming a constant speed for any given galaxy; the Hubble time is calculated by tracing the Universe backward in time using the current Hubble's constant
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peculiar motion
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the motion of a galaxy with respect to the Hubble flow
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cosmological principle
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the principle that on the whole the Universe looks the same in all directions and in all regions
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critical density
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the density of matter that would allow the Universe to expand forever, but at a rate that would decrease to 0 at infinite time. The density of the Universe with respect to this defines whether the Universe will expand forever or eventually contract, assuming there is no gravitationally repulsive dark energy
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average density of matter
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the ratio of this compared to the a specific critical density determines the ultimate fate (whether the expansion ever stops or reverses) of the Universe
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?M ; 1
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closed universe
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?M = 1
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flat (critical universe)
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?M ; 1
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open universe
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?M
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the ratio of average density of matter to critcal density
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flat (critical) universe
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a universe in which Euclid's parallel postulate holds. It barely expands forever, assuming there's no gravitationally repulsive energy. It has an infiinte volume and its age is 2/3 the Hubble time (assuming no dark energy)
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open universe
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a big-bang cosmology in which the Universe has infinite volume and will expand forever
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closed universe
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a bing-bang universe with positive curvature. It has finite volume and will eventually contract, assuming there's no gravitationally repulsive energy
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accelerating universe
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The model for the Universe based on observations late in the 1990s that the expansion of the Universe is speeding up over time, rather than slowing down in the way that gravity alone would modify its expansion
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quantum flucuation
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the spontaneous formation and disappearance of virtual particles; it may be a quantum violation of the classical law of conservation of energy because of Heisenberg's Uncertainty Principle
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dark matter
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non-luminous matter
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the stelliferous era
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the current era, with lots of stars in the Universe
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the degenerate era
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the future era when the Universe will be filled with cold brown dwarfs, white dwarfs, and neutron stars. (Blakc holes will also exist).
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the black-hole era
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the future era, following the degenerate era, when only the objects (besides photons and subatomic particles) the Universe will be black holes
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the dark era
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the finale era of the Universe, when only low-energy photons, neutrinos, and some elementary particles(the ones that did not find a partner to annihilate) remains
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black dwarf
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a feebly raidating ball of gas that results when a white dwarf has radiated nearly all its energy
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brown dwarf
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a self-gravitating, self-luminous object, insufficiently massive for sustained nuclear fusion (less than 0.075 solar mass)
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white dwarf
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the final stage in the evolution of a star initially between 0.075 and about 8 or 10 solar masses but with a final mass no larger than 1.4M. It is supported by lectron degeneracy pressure and are found on the lower left og the main sequence of the temperature-luminosity diagram
