Flash Cards

Various astronomy terms

Term Definition
Celestial sphere An imaginary, giant, hollow sphere with the earth in the center and the sun, moon, stars, and other planets on it's inner surface.
Horizon The line that separates the visible portion of the celestial sphere from the part we cannot see.
Celestial poles The points on the celestial sphere that are directly overhead at the earth's poles.
Circumpolar Always above the horizon.
Zodiac The imaginary band on which the sun moon and planets appear.
Constellation A group of celestial bodies contained within certain boundaries.
Asterism A small group of stars used to form a picture.
Sun The closest and most important star to us.
Core of the sun The center of the sun.
Photosphere The visible part of the sun.
Granule A convection cell on the surface of the sun about 600 miles long.
Supergranule Convection cells on the sun's surface about 22000 miles long.
Sunspots Cool spots on the sun caused by its magnetic field.
Chromosphere The lowest layer of the sun's atmosphere, called the sphere of color.
Spicule Columns of gas erupting from the chromospere.
Solar flares A tremendous burst of energy caused by magnetic stress within the sun.
Solar prominence Streams of dense gas erupting off the chromosphere and returning in a loop like fashion.
transition region The layer of the sun's atmosphere above the chromosphere.
Corona The outermost layer of the sun's atmosphere.
Coronagraph A device that blocks light from the photosphere.
Light-year The distance light travels in one year.
Parallax The change in an object's position caused by an observers change in position.
Apparent magnitude The brightness of a star as it appears from earth.
Absolute magnitude The apparent magnitude viewed from 10 parsecs.
Hertzsprung-Russell diagram A chart used for classifying stars
Giants or supergiants Large cool stars whose brightness is caused by size.
Stars of the main sequence Average stars whose temperature depends on heat.
White dwarf A very hot but dim star due to its size.
Binary star A system in which two stars are bound together by gravity.
Optical doubles Stars that are close on the celestial sphere but far apart in space.
Open cluster Asymmetrical clumps containing tens hundreds or thousands of stars.
Globular cluster Tightly clumped spherical groups of thousands or millions of stars.
Nova An occurrence taking place when a star flares up many times its original brightness.
Supernova A nova resulting in the explosion of a star.
Neutron star The hot core of a star left after a supernova.
Pulsar A rapidly rotating neutron star that emits radio waves.
Galaxy A massive star system containing millions or billions of stars.
Clusters The smallest division in groups of galaxies.
Supercluster A group of several clusters.
Spiral galaxy A galaxy shaped with large arms spiraling from the nucleus.
Black hole An object so large and dense no matter can escape its gravity.
Elliptical galaxy Egg-shaped galaxies.
Lenticular galaxy A flat galaxy with a bulging nucleus.
irregular galaxy galaxies with no definite shape.
Quasar An extremely bright object that emits light and radio waves.
Accretion disc A glowing ring of gas.
Nebulae Large clouds of gas floating in space.
Solar wind A high speed stream of charged particles ejected from the sun.
Orbit Circle around due to gravity.

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