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45 Cards in this Set
- Front
- Back
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Sa, SBa spiral |
Tightly wound arms and large bulge lol |
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Sb, SBb spiral |
Moderately wound arms and moderate-sized bulge |
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Sc, SBc spiral |
loosely wound arms and small bulge |
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Closest spiral galaxy to Milky Way |
Andromeda Galaxy |
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Flocculent spiral |
Poorly defined spiral arms |
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Grand-design spiral |
Well-defined spiral arms |
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E0 |
Elliptical galaxy, circular |
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E4 |
Somewhat oval |
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E7 |
Very oval |
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Irr I |
Some hints of organization |
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Irr II |
Highly distorted |
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Lenticular galaxy |
Has a bulge and a disk, but no spiral arms |
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Harlow Shapley |
Revealed true size by observations of Cepheid variables in globular clusters |
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Sagittarius A |
Nucleus of the galaxy |
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Diameter of Milky Way |
100,000 light years |
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# of stars in the Milky Way |
200 billion |
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Gravitational lensing |
Focusing of light by mass |
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Dark matter |
Rotation curve of the Milky Way; stars far from center orbit as quickly as stars closer to the center |
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Cluster |
Gravitationally bound collections of galaxies |
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Rich clusters |
more than 1000 galaxies; spherical shape with most galaxies near the center |
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Poor clusters |
a few dozen galaxies & no recognizable shape |
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Local Group |
cluster of ~40 galaxies that contain the Milky Way and Andromeda galaxy |
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Regular cluster |
Spherical cluster of galaxies with concentration of galaxies @ center; ellipticals and lenticulars |
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Irregular cluster |
randomly scattered galaxies; ellipticals, lenticulars, spirals |
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Hubble law |
recessional velocity = Hubble constant x distance |
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Hubble constant |
74 km/sec/Mpc |
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Hubble flow |
Galaxies in distant clusters and superclusters are moving away from us faster than galaxies in nearby clusters |
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Standard candle |
object with known brightness which enables astronomers to calculate distance; Cepheids and Type Ia supernovae |
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Collision of galaxies |
Triggers star formation; results in creation of elliptical galaxy |
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Quasars |
objects that look like stars but emit huge amounts of energy |
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Active Galactic Nuclei (AGNs) |
powerful emission sources at the centers of galaxies; powered by accretion of matter onto supermassive black holes |
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Seyfert galaxies |
Similar to quasars but less luminous; often spiral, strong emission lines, less distant than quasars |
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Radio galaxies |
galaxies w/ strong radio emission; can extend over millions of light years |
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BL Lacertae objects (BL Lacs) |
very weak emission lines and very strong variability; rare |
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Age of universe |
13.7 billion years |
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Cosmic microwave background |
leftover radiation from the plasma that formed after the Big Bang |
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The Four Forces |
gravity, electromagnetism, strong nuclear force, weak nuclear force |
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Gravity |
attraction between massive particles, acts over infinite distances |
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Electromagnetism |
interaction between charged particles, can act over infinite distances but usually doesn't |
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Strong nuclear force |
hold protons and neutrons together in atomic nuclei |
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Weak nuclear force |
involved in radioactive decay |
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Structure of universe |
Clusters of galaxies form superclusters, which appear to be arranged in sheets, forming a honeycomb-looking structure |
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Inflation |
period of extreme expansion of the universe |
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Pair production |
creation of particles and antiparticles |
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Drake equation |
number of technologically advanced civilizations in our galaxy that we could detect |
