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. |