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Unit 2 Part 2
Part 2 Astromony Vocabulary
| Term | Definition |
|---|---|
| Photosphere | the region of the sun that radiates energy into space; visible surface of the sun. |
| Chromoshere | the first layer of the solar atmopshere found directly above the photosphere. |
| Corona | the outer weak layer of the solar atmosphere. |
| Solar Wind | steams of protons and electrons ejected at high speed from the solar corona. |
| Sunspot | a darkspot on the sun, which is cool by constrast to the surrounding photosphere. |
| Pronminence | a concentration of gases above the solar surface that appears as a bright archlike structure. |
| Solar Flare | a sudden and tremendous eruption in the solar chromosophere. |
| Aurora | a bright display of ever-changing light caused by solar radiation interacting with the upper atmosphere in the region of the poles. |
| Nuclear fusion | the way in which the sun produces energy; Nuclear fusion occurs when less massive nuclei, releasing tremendous amounts of energy. |
| Constellation | an apparent group of stars originally named for mythical characters; The sky is presently divided into 88 constelations. |
| Binary star | one of two stars revolving around a common center of mass under their mutual gravitational attraction. |
| Light-year | The distance light travels in a year. |
| Apparent magnitude | the brightness of a star when veiwed from Earth. |
| Absolute magnitude | the apparent brightness of a star if it were viewed from a distance of 32.6 light-years; used to compare the true brightness of stars. |
| Main-sequence star | a star that falls into the main sequence category on the H-R diagram; This category contains the majority of stars and runs diagonally from the upper left to the right on the H-R diagram. |
| Red giant | a large, cool star of high luminosity; a star occupying the upper- right portion of the H-R diagram. |
| Supergiant | a very large, very bright star. |
| Cepheid variable | a star whose brigthness varies periodically because it expands and contrasts; a type of pulsating star |
| Nova | a star that explosively increases in brightness |
| Nebulae | muliple clouds of gas and/or dust in space. |
| Hertzsprung-Russell Diagram | a plot of stars according to their absolute magnitudes and temperatures. |
| Protostar | a collapsing cloud of gas and dust destined to become a star; a developing star not yet hot enough to engage in nuclear fusion |
| Supernova | an exploding star that increases in brightness many thousands of times. |
| White dwarf | a star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size, belived to be near its final stage of evolution. |
| Neutron star | a star of extreamly high density composed entirely of neutrons. |
| Pulsar | a variable radio source of a small size that emits radio pulses in very regular periods. |
| Black hole | a massive star that has collapsed to such a small volume that its gravity prevents the escape of everything, including light. |
| Galaxy | a group of stars, dust, and gases held together by gravity. |
| Hubble's law | a law that states that the galaxies are retreating from the Milky Way at a speed that is proportional to their distance. |
| Big Bang Theory | the theory that proposes that the universe originated as a single mass, which subsequently exploded. |
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