
Standard view
Full view
of .
Look up keyword
Like this
0 of .
Results for:
No results containing your search query
P. 1
An Astronomy Glossary

An Astronomy Glossary

Ratings: (0)|Views: 837|Likes:
Published by IWantToBelieve8728

More info:

Published by: IWantToBelieve8728 on Sep 03, 2008
Copyright:Attribution Non-commercial


Read on Scribd mobile: iPhone, iPad and Android.
download as PDF, TXT or read online from Scribd
See more
See less





AA ring
One of three Saturnian rings visible from Earth. The Aring is farthest from the planet and is separated fromthe B ring by the Cassini division.
absolute brightness
The apparent brightness a star would have if it wereplaced at a standard distance of 10 parsecs (32.6light-years) from Earth.
absolute magnitude
The apparent magnitude a star would have if it wereat a distance of 10 parsecs (32.6 light-years) fromthe sun.
absorption line
Dark line in an otherwise continuous bright spectrum,where light within one narrow frequency range hasbeen removed.
absorption spectrum
Spectrum in which the radiation is distributed over allfrequencies, except at a few specific frequencies. It isproduce by light from a continuous spectrum sourcethat passes through a low density gas. The gasabsorbs the same frequencies that it would emit if heated.
The rate of change of velocity of a moving object.
Gradual growth of bodies, such as planets, by theaccumulation of other, smaller, bodies.
accretion disk
Flat disk of matter spiraling down onto the surface of a star or black hole. Often, the matter originated onthe surface of a companion star in a binary system.
active galaxy
The most energetic galaxies, which can emithundreds or thousands of times more energy persecond than the Milky Way.
active optics
Collection of techniques now being used to increasethe resolution of ground-based telescopes. Minutemodifications are made to the overall configuration of an instrument as its temperature and orientationchange, to maintain the best possible focus at alltimes.
active region
Region of the photosphere of the Sun surrounding asunspot group, which can erupt violently andunpredictably. During sunspot maximum, the numberof active regions is also a maximum.
active Sun
The unpredictable aspects of the Sun's behavior, suchas sudden explosive outbursts of radiation in the formof prominences and flares.
adaptive optics
Technique used to increase the resolution of atelescope by deforming the shape of the mirror'ssurface under computer control while a measurementis being taken, to undo the effects of atmosphericturbulence.
Layer of the Earth's interior, just below thelithosphere, over which the surface plates slide.
The average percentage of light reflected from asurface. Also called the reflectivity of a surface.
amino acids
Organic molecules which form the basis for buildingthe proteins that direct metabolism in livingcreatures.
The maximum deviation of a wave above or belowthe zero point.
angular momentum problem
The fact that the Sun, which contains nearly all of themass of the solar system, accounts for just 0.3percent of the total angular momentum of the solarsystem. This is an aspect of the solar system that anyacceptable formation theory must address.
angular resolution
The ability of a telescope to distinguish betweenadjacent objects in the sky.
annular eclipse
Solar eclipse occurring at a time when the Moon is farenough away from the Earth that it fails to cover thedisk of the Sun completely, leaving a ring of sunlightvisible around its edge.
The point on the elliptical path of an object in orbitabout the Sun that is most distant from the Sun.
Apollo asteroid
See Earth-crossing asteroid.
apparent brightness
The brightness that a star appears to have, asmeasured by an observer on Earth.
apparent magnitude
A measure of the apparent brightness of a star asseen from the earth. The scale is based on thefaintest stars visible to the unaided eye in a cleardark sky. These stars are given a magnitude value of 6.0. A star 100 time brighter will have a magnitudevalue 5 less or 1.0. A star 100 times fainter will havea value 5 greater or 11.0. See the Pogson Scale.
arc degree
Unit of angular measure. There are 360 arc degreesin one complete circle.
Small grouping of (typically 100 or less) stars,spanning up to a few tens of parsecs across, usuallyrich in very young stars.
One of thousands of very small members of the solarsystem orbiting the Sun. Most are found between theorbits of Mars and Jupiter. They very in size from1000 km in diameter down to a few meters. Seemeteoroids. Asteroids are often referred to as "minorplanets".
asteroid belt
A region of the solar system, between the orbits of Mars and Jupiter, in which most asteroids are found.
astronomical unit
A measure of distance that is equal to the averagedistance between the center of the sun and thecenter of the earth. It is equal to approximately93,000,000 miles or 150,000,000 kilometers. Thecommon abbreviation is AU. Precise radarmeasurements yield a value for the AU of 149,603,500 km.
Branch of science dedicated to the study of everything in the universe that lies above Earth'satmosphere.
asymptotic giant branch
Path on the H-R diagram corresponding to thechanges that a star undergoes after helium burningceases in the core. At this stage, the carbon coreshrinks and drives the expansion of the envelope,and the star becomes a swollen red giant for asecond time.
A layer of gas confined close to a planet's surface bythe force of gravity. The earh's atmosphere extendsabout 150 km above the surface.
Building block of matter, composed of positivelycharged protons and neutral neutrons in the nucleus,
surrounded by negatively charged neutrons.
Abbreviation for Astronomical Unit.
Event which occurs when atmospheric molecules areexcited by incoming charged particles from the solarwind, then emit energy as they fall back to theirground states. Aurorae generally occur at highlatitudes, near the north and south magnetic poles.
autumnal equinox
(i) Date on which the Sun crosses the celestialequator moving southward, occurring on or nearSeptember 22.(ii) The location in the sky marked by the direction tothe sun on date the Autumnal Equinox occurs. Thislocation remains whether the sun is actually there ornot.
BB ring
One of three Saturnian rings visible from Earth. The B ring is thebrightest of the three, and lies just past the Cassini division, closerto the planet than the A ring.
barred-spiral galaxy
Spiral galaxy in which a bar of material passes through the centerof the galaxy, with the spiral arms beginning near the ends of thebar.
baryonic matter
Matter that is composed primarily of baryons-protons andneutrons. "Normal" matter.
The distance between two observing locations used for thepurposes of triangulation measurements. The larger the baseline,the better the resolution attainable.
Dark, low-pressure region, where gas flows downward in theatmosphere of a jovian planet.
Big Bang
Event that cosmologists consider the beginning of the universe, inwhich all matter and radiation in the entire universe came intobeing.
binary-star system
A system which consists of two stars in orbit about their commoncenter of mass, held together by their mutual gravitationalattraction. Most stars are found in binary-star systems.
black dwarf 
The end-point of the evolution of an isolated, low-mass star. Afterthe white dwarf stage, the star cools to the point where it is a dark"clinker" in interstellar space.
black hole
A region of space where the pull of gravity is so great that nothing-not even light-can escape. A possible outcome of the evolution of avery massive star.
black-body curve
The characteristic way in which the intensity of radiation emittedby a hot object depends of frequency. The frequency at which theemitted intensity is highest is an indication of the temperature of the radiating object. Also referred to as the Planck curve.
A (hypothetical) perfect radiator/absorber of electromagneticradiation that absorbs and re-emits all light that falls on it. Thecharacteristics of the energy radiated depends only on thetemperature of the object.
blackbody spectrum
The continuous spectrum emitted by a blackbody. The flux at eachwavelength is given by a formula known as Planck's Law.
blue giant
Large, hot, bright star at the upper left end of the main sequenceon the H-R diagram. Its name comes from its color and size.

Activity (18)

You've already reviewed this. Edit your review.
1 hundred reads
1 thousand reads
Chloe Hayes liked this
Dan liked this
Dan liked this
Murali Krishnan liked this
Murali Krishnan liked this
Murali Krishnan liked this
KIMVEN72 liked this

You're Reading a Free Preview
