Science Bowl Astronomy Study Guide
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40 terms
Terms | Definitions |
|---|---|
 Albedo | Amount of sunlight that is reflected by the surface of a planet or a satellite, such as the Moon. |
| Aphelion | The point in an orbit in which an object is at its farthest possible distance from the Sun. |
| Apogee | The point in an orbit in which an object is at its farthest possible distance from the Earth. |
| Astronomical Unit (AU) | Mean distance from the Earth to the Sun. |
| Aurora | Glow in the Earth's ionosphere caused by the interaction between Earth's B-field and charged particles from the Sun (solar wind) |
| Cepheid Variable | A star of variable luminosity. The luminosity increases sharply and falls off gently with a well-defined period. The period is related to the absolute luminosity of the star and so can be used to estimate the distance to the star. |
| Chromosphere | Layer between photosphere and corona of the Sun, mainly composed of excited hydrogen atoms |
| Conjunction | When 2 bodies appear very close together in the sky |
| Eccentricity | Ratio of distance between the two foci to the length of the major axis |
| Eclipse | The obstruction of a heavenly body by its entering into the shadow of another body. |
| Ecliptic | the great circle representing the apparent annual path of the sun |
| Equinox | The time when the Sun crosses the celestial equator. -The vernal (Spring) |
| Galilean Moons | The name given to Jupiter's four largest moons, Io, Europa, Callisto & Ganymede. They were discovered independently by Galileo Galilei and Simon Marius. |
| Magnetosphere | The region of space where a planet's magnetic field dominates that of the solar wind |
| Occultation | When one celestial body passes in front of and obscures the other. |
| Parallax | The angular difference in apparent direction of an object seem from 2 different viewpoints |
| Parsec | A large distance often used in astronomy. A parsec is equal to 3.26 light-years. (Short for "parallax second") |
| Penumbra | Outer shadow cast during eclipses, the region of shadow that gives rise to a partial eclipse. Also the lighter area surrounding the central region of a sunspot. |
| Perigree | The point in an orbit in which an object is at its closest possible distance from the Earth. |
| Perihelion | The point in an orbit in which an object is at its closest possible distance from the Sun. |
| Photosphere | The Sun's outer, visible surface. |
| Precession | Circular motion about the axis of rotation of a body, fixed with respect to the stars. |
| Prominence | A cloud of hot, luminous gas in the Sun's corona. |
| Pulsar | Rapidly rotating Neutron star that emits strong electromagnetic radiation in 2 tightly focused beams in the forms of radio waves, X rays, and gamma rays |
| Quasar | Compact, extra galactic objects at large distances. Highly luminous. |
| Red Giant | Spectral type K or type M star that's near the end of its life. Has low surface temperature and large diameter. |
| Red Shift | (astronomy) a shift in the spectra of distant galaxies toward longer wavelengths |
| Resolution | The amount of small detail visible in an image |
| Retrograde | Rotation of a planet, or orbit, opposite that of what's normally seen. |
| Sidereal Time | Star time, hour angle of vernal equinox |
| Sidereal Month | Period of Moon's orbit |
| Solar Flare | Sudden and short-lived burst of energy on the Sun's surface. Lasts from minutes to hours. |
| Solar Wind | Stream of charged particles emitted from the Sun which travels into space along magnetic flux lines |
| Solstice | The time when the Sun reaches its most northerly point or southerly point (around June 21 or December 22). It marks the beginning of summer/winter. |
| Sunspot | Cooler region of Sun's photosphere, seen as a spot on the Sun's disc. Caused by concentrations of magnetic flux typically occurring in groups or clusters. |
| Umbra | Shadow area defining a total eclipse, or the dark central region of a sunspot. |
| Variable Star | Any star whose brightness or magnitude varies with time |
| White Dwarf | A white star with 1.4 solar masses and about the size of the Earth |
| Wormhole | Hypothetical shortcut through space-time continuum |
| Zenith | Highest point in the sky reached by a celestial body |
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