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Astronomy part 2
Vocab words for astronomy
| Term | Definition |
|---|---|
| Photosphere | the luminous envelope of a star from which its light and heat radiate. |
| Chromosphere | a reddish gaseous layer immediately above the photosphere of the sun or another star. Together with the corona, it constitutes the star's outer atmosphere. |
| Corona | the rarefied gaseous envelope of the sun and other stars. The sun's corona is normally visible only during a total solar eclipse when it is seen as an irregularly shaped pearly glow surrounding the darkened disk of the moon. |
| Solar Wind | the continuous flow of charged particles from the sun that permeates the solar system. |
| Sunspot | a spot or patch appearing from time to time on the sun's surface, appearing dark by contrast with its surroundings. |
| Prominence | an eruption of a flamelike tongue of relatively cool, high-density gas from the solar chromosphere into the corona where it can be seen during a solar eclipse or by observing strong spectral lines in its emission spectrum. |
| Solar Flare | a brief eruption of intense high-energy radiation from the sun's surface, associated with sunspots and causing electromagnetic disturbances on the earth, as with radio frequency communications and power line transmissions. |
| Aurora | a natural electrical phenomenon characterized by the appearance of streamers of reddish or greenish light in the sky, usually near the northern or southern magnetic pole. |
| Nuclear fusion | a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy. |
| Constellation | a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure. Modern astronomers divide the sky into eighty-eight constellations with defined boundaries. |
| Binary star | a system of two stars in which one star revolves around the other or both revolve around a common center. |
| Light-year | a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 trillion miles). |
| Apparent magnitude | the magnitude of a celestial object as it is actually measured from the earth. |
| Absolute magnitude | the magnitude (brightness) of a celestial object as it would be seen at a standard distance of 10 parsecs. |
| Main-sequence star | any star that is fusing hydrogen in its core and has a stable balance of outward pressure from core nuclear fusion and gravitational forces pushing inward. |
| Red Giant | a very large star of high luminosity and low surface temperature. Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion. |
| Supergiant | a very large star that is even brighter than a giant, often despite being relatively cool. |
| Cepheid variable | a variable star having a regular cycle of brightness with a frequency related to its luminosity, so allowing estimation of its distance from the earth. |
| Nova | a star showing a sudden large increase in brightness and then slowly returning to its original state over a few months. |
| Nebula | a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter. |
| Hertzsprung-Russel Diagram | a two-dimensional graph, devised independently by Ejnar Hertzsprung (1873–1967) and Henry Norris Russell (1877–1957), in which the absolute magnitudes of stars are plotted against their spectral types. |
| Protostar | a contracting mass of gas that represents an early stage in the formation of a star, before nucleosynthesis has begun. |
| Supernova | a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass. |
| White dwarf | a small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula. |
| Neutron star | a celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons. |
| Pulsar | a celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second. |
| Black hole | a region of space having a gravitational field so intense that no matter or radiation can escape. |
| Galaxy | a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction. |
| Hubble's law | A law of cosmology stating that the rate at which astronomical objects in the universe move apart from each other is proportional to their distance from each other. |
| Big Bang Theory | The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution. |
Created by:
Matthew S
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