Astronomy Final Exam
Terms
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- lenticular galaxy
- disk-shaped galaxy without spiral arms
- nuclear bulge
- a distribution of stars in the shape of a flattened sphere that surrounds the nucleus of a spiral galaxy like the Milky Way
- synchrotron radiation
- radiation emitted by charged particles moving through a magnetic field; nonthermal rotation
- spiral arm
- lanes of interstellar gas, dust, and young stars that wind outward in a plane from the central regions of some galaxies
- nebula
- a cloud of interstellar gas and dust
- spin (of an electron or proton)
- a small, well-defined amount of angular momentum possessed by electrons, protons, and other particles
- rich cluster (of galaxies)
- cluster of galaxies with many members
- Hubble flow
- the recession of the galaxies caused by the expansion of the universe
- irregular galaxy
- an asymetrial galaxy having neither spiral arms nor an elliptical shape
- Hubble constant
- the constant of proportionality in the relation between the recessional velocities of remote galaxies and their distances; the correct value will determine the age of the universe
- poor cluster (of galaxies)
- cluster of galaxies with only a few members
- galaxy
- a large assemblage of stars, gas, and dust bound together by their mutual gravitational attraction
- cluster (of galaxies)
- a collection of a few hundred to a few thousand galaxies bound by gravity
- standard candle
- object whose known luminosity can be used to deduce the distance to a galaxy
- gravitational lensing
- the distortion of the appearance of an object by a source of gravity between it and the observer
- peculiar galaxy
- any Hubble class of galaxy that appears to be blowing apart
- radio galaxy
- a galaxy that emits an unusually large amount of radio waves
- halo (of a galaxy)
- a spherical distribution of globular clusters, isolated stars, and possibly dark matter that surrounds a galaxy
- radio lobe
- vast regions of radio emission on opposite sides of a radio galaxy
- Milky Way galaxy
- solar system in which our solar system resides
- Local Group
- the cluster of about 40 galaxies (in which our own galaxy is a member)
- BL Lacertae (BL Lac) object
- a type of galaxy; a blazar
- elliptical galaxy
- galaxy with an elliptical shape, little interstellar matter, and no spiral arms
- organic molecule
- carbon-based compound
- galactic merger
- a collision and subsequent merger of two roughly equal-sized galaxies
- quasi-stellar object
- a quasar
- supercluster (of galaxies)
- a gravitationally bound collection of many clusters of galaxies
- spiral galaxy
- a flattened, rotating galaxy with pinwheel-like spiral arms winding outward from the galaxy's nuclear bulge
- 21-cm radio radiation
- radio emission from a hydrogen atom caused by the flip of the electron's spin orientation
- Seyfert Galaxy
- spiral galaxy w/ bright nucleus whos spectrum exhibits emission lines
- blazar
- a BL Lacertae object
- starburst galaxy
- galaxy where there is an exceptionally high rate of star formation
- regular cluster (of galaxies)
- evenly distributed group of galaxies bound together by mutual gravitational attraction
- Einstein Ring
- circular or arc-shaped image of a distant galaxy or quasar
- intergalactic gas
- gas located between the galaxies within a cluster of galaxies
- galactic nucleus
- center of a galaxy; the center of the Milky Way galaxy
- galactic cannibalism
- a collision between two galaxies of unequal mass and size in which the smaller galaxy is absorbed by the larger galaxy
- Shapely-Curtis debate
- an inconclusive debate in 1920 about whether certain nebulae were beyond the Milky Way
- rotation curve (of a galaxy)
- a graph showing how the orbital speed of material in a galaxy depends on the distance from the galaxy's center
- dark matter (missing mass)
- the as-yet-undetected matter in the universe that is underluminous and probably quite different from ordinary matter
- disk (of a galaxy)
- a flattened assemblage of stars, gas, and dust in a spiral galaxy like the Milky Way
- Sagittarius A
- the strong radio source associated with the nucleus of the Milky Way galaxy
- trailing-arm spiral galaxy
- a spiral arm pointing away from the direction of roration, characteristic of all spiral galaxies
- Tully-Fisher relation
- correlation between the width of the 21-centimeter line of a spiral galaxy and its absolute magnitude
- barred spiral galaxy
- spiral galaxy in which the spiral arms begin from the ends of a bar running through the nuclear bulge
- water hole
- part of electromagnetic spectrum at a few thousand megahertz- very little background noise from space
- quasar
- a starlike object w/ a very large redshift
- distance modulus
- the difference between the apparent and absolute magnitudes of an object
- irregular cluster (of galaxies)
- an unevenly distributed group of galaxies bound together by their mutual gravitational attraction
- SETI
- the Search for Extra Terrestrial Intelligence
- active galaxy
- very luminous galaxy, often containing an active galactic nucleus
- Hubble law
- the redshifts of remote galaxies are directly proportional to their distances from Earth
- microlensing
- the gravitational focusing of light from a distant sar by a closer object to give a brighter image of the star
- Hubble classification
- a system of classifying galaxies according to their appearance into one of four broad categories: spirals, barred spirals, ellipticals, and irregulars
- double radio source
- two large lobes of radio emission, often located on either side of an active galaxy
- spiral density wave
- a spiral-shaped pressure wave that orbits the disk of a spiral galaxy and induces new star formation
- Einstein Cross
- appearance of 4 images of the same galaxy or quasar due to gravitational lensing
- head-tail source
- a radio galaxy whose radio emission is deflected from the galaxy