Asteroid - a small body, similar in composition to one of the terrestrial planets. Asteroids come in a wide variety of sizes in shapes. The majority of asteroids are found in the asteroid belt between the planets Mars and Jupiter. It is believed that the asteroids there would have formed into a planet had Jupiter's gravitational forces not been so strong as to disrupt that formation

Asteroid Belt - the area of space in our solar system between Mars and Jupiter where the majority of the asteroids are found. It is believed that a planet would have formed here if not for Jupiter's strong gravitational affects disrupting the planets formation

Astronomical Unit (AU) - a unit of measurement for distances in the solar system. One AU is the average distance from the Earth to the sun and is equal to approximately 149,600,000 kilometers (92,956,000 miles)

Astronomy - branch of science dealing with stars, solar systems, galaxies, or any celestial body in the universe

Atmosphere - a collection of gases trapped by a celestial body's gravitational field. The gases surrounding the planet cause pressure (the weight of the gas as felt by some location on the surface) and can also filter out (or keep in) energy sent by the sun

Aurora - a magnificent light show seen in the atmosphere of a planet when charged particles from sunspots get trapped in the magnetic field of the planet. They released their energy and cause reaction in the atmosphere causes the sky to light up in ribbons of various colors. Auroral affects are most often visible closer to the poles of a planet

Axis of Rotation - an imaginary line around which a celestial body spins. Most of the planets tend to have their axis perpendicular to the ecliptic, bot not all of them

Big Bang Theory - states that all the matter in the universe existed in a single point in space. This point exploded and the resulting temperature caused the subatomic particles to join together to form the first atoms of hydrogen and helium

Black Hole - caused by the death of an extremely large star, black holes have gravitational fields strong enough to trap light. Black holes consist of a singularity, the center where all the mass resides, and an event horizon, a black disk encircling the singularity and the point at which light can no longer escape the gravitational forces of the black hole

Celestial - anything pertaining to the sky, heavens, space, etc.

Comet - comets are similar to asteroids but contain much more ice in them. When they pass the orbit of Jupiter and approach the sun, the ice sublimates and creates a ball of gas around the comet. The solar wind then blows the gas away from the comet, creating the part of a comet most known by people, its tail

Constellation - a collection of stars that form the shape of another object. There are 88 named constellations. The stars that make up a constellation are not necessarily close to each other in space, rather they simply appear in the same area of the sky when viewed from Earth

Convection Zone - the outer third layer of the sun. The energy created in the core of the sun is transported through the convection zone similar to boiling water. The gases of the convection zone seem to "bubble" to the top and release the energy

Core - innermost part of a star where nuclear reactions take place

Coronal Mass Ejection - when a large amount of the corona (the outer layer of the sun) is ejected into space. This happens in small amount with the solar wind. Larger amounts of the corona, as seen in a coronal mass ejection, can cause havoc with electrical equipment here on Earth

Cosmology - study of the universe, including its structure, origin, evolution, and future

Density - the ratio of the mass of a body to its volume

Dwarf, Black - the remnant of a white dwarf; a white dwarf that has ceased to shine

Dwarf, Brown - a forming star that did not have enough mass to reach the temperature necessary to start nuclear fusion

Dwarf, White - the remnant of a low-mass star. White dwarfs are the core of the star in the process of converting helium to carbon and oxygen. They are very small, but very hot

E=MC^2 - equation giving the amount of energy in any given amount of mass. By multiplying the mass by the speed of light, squared, the energy can be determined

Eccentric - not circular; elliptical. See also ellipse

Eclipse - the blocking of one celestial object by another, specifically an object casting its shadow on another object

Ecliptic - plane of space where roughly all of the planets lie

Einstein - physicist who came up with the Theory of Relativity and E=MC^2

Ellipse - an oval; an ellipse has two focus points.

Event Horizon - black disk encircling a black hole. The event horizon is the point at which light can no longer escape the gravitational forces of the black hole. The radius of the event horizon can be calculated by the equation Rs=2GM/C^2

Food Chain - link between food sources. A simple food chain may start with plants, then herbivores, and then carnivores. If any part of the food chain is damaged, the entire chain would collapse

Galaxy - A collection of stars orbiting around a common center. Galaxies also contain star clusters, hydrogen gas, and cosmic rays

Global Warming - warming of a planet due to the greenhouse effect

Gravity - the property of mutual attraction of two objects having mass. The force of gravity is equal to the mass of the first object, times the mass of the second object, times the gravitational constant (6.7e-11), divided by the distance between the two objects or: Fg=GM1M2/R^2

Great Dark Spot - a large storm raging on the planet Neptune

Great Red Spot - a large storm raging on the planet Jupiter

Greenhouse effect - the result of greenhouse gases trapping the suns infrared radiation on a planet. Without the presence of greenhouse gases, infrared radiation would reflect off the surface of the planet and back into space. With greenhouse gases, however, the infrared radiation is trapped in the atmosphere and results in global warming

Greenhouse gases - gases associated with the greenhouse effect including carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons (CFCs)

Heat - the result of the collision between atoms in a substance

Heliocentric - the belief that the sun, not the Earth, was the center of the universe. Copernicus is credited for garnering wide-spread support for this belief

Hemisphere, Northern - the northern half of the Earth; all parts of the Earth north of the equator

Hemisphere, Southern - the southern half of the Earth, all parts of the Earth south of the equator

Hertzprung-Russel Diagram - a diagram plotting a star's luminosity vs. surface temperature. Using a HR Diagram stars fall into four different areas. These areas can then be used to determine which stage in life a star has reached

Industrial Revolution - the movement of different countries from a society based largely on agriculture to one based more upon the mechanized production of manufactured goods

Kepler's Three Laws of Planetary Motion - Kepler's three laws describing the motion of the planets around the sun

Planets move in elliptical orbits with the sun at a focus

Planets sweep out equal areas in equal times

The ratio of a planets period, squared, to is radius, cubed is proportional

Light Pollution - man-made light drowning out the light of the stars. This is most notable near a large city

Little Ice Age - the period of time between 1645 and 1715 where most of Europe experienced extremely cold temperatures. Although not as severe as the Ice Ages that occur every 150 million years or so

Luminosity - the measure of the absolute brightness of a star. Luminosity has much to do with the amount of power put out by the star as well as the size of the star

Lutheran - a Christian denomination; as called Protestants or Evangelists

Magnetic Field - the area around an object that will react with another magnetic object. Planets have magnetic fields about them. These fields interact with the charged particles streaming from the sun. Evidence of this can easily be seen by watching the aurora

Main Sequence - the section of the HR Diagram that runs from the upper-left hand corner to the lower-right hand corner and characterizes stars in the main stage of their life; the stage at which they fuse hydrogen and helium in their core

Meteor Shower - when Earth passes through the debris left by a comet, the small particles of dust and rocks enter the Earth's atmosphere. There they are heated by friction and begin to glow. These are called "shooting stars" or "falling stars"

Moon - a natural satellite orbiting a planet

Nebula - a cloud of interstellar gas and dust made up mostly of hydrogen and helium. Nebulas come in different forms; planetary nebulas, supernova remnants, and diffuse nebulas. When stars form, they form as a result of a nebula condensing

Neutron Star - the remnant of a high-mass star. The gravity of these stars is strong enough to knock the electrons out of their orbit and into the nucleus of the atoms. There, they form with protons to form neutrons. The structure of the nucleus is strong enough to resist any further gravitational collapse

Newton's Third Law of Motion - states that for every action, there is an equal, and opposite, reaction. E.g. when you jump into the air, there is a force equal and opposite to the one that moved you upward. The reason the Earth doesn't seem to move away from you is that it is large enough that your pushing it had almost no affect

Nuclear Fusion - the process of combining two lighter elements to form a heavier element. Nuclear fusion is the source of energy in stars. The most common nuclear fusion is that of hydrogen to helium. The most difficult thing to accomplish with nuclear fusion is to heat the elements to the necessary temperature for the reaction to occur. It takes around ten million degrees Kelvin before hydrogen will fuse into helium

Orbit - the path of an object through space. This path is usually affected gravitationally by another object, causing it to be curved. Kepler's First Law of Planetary Motion describes such a curve in the orbit of the planets

Outer Layers - When referring to the outer layers of the sun we are usually referring to the convection zone and, within that, the chromosphere, photosphere, and corona

Period - the amount of time it takes a body to perform one rotation or revolution. In the case of Kepler's Third Law of Planetary Motion it is the time it takes for a planet to complete one revolution, or one orbit about the sun

Photosynthesis - the process by which plants produce energy. By combining carbon dioxide, water, and sunlight, plants are able to produce sugar for energy

Planet - any larger bodies that orbit around the sun and are illuminated by the sun and not by an internal light source

Planetary Nebula - see nebula

Polar Cap - the polar region of a planet. Typically it is colder than the rest of the planet so elements that exist as either a liquid or a gas on other parts of the planet are more likely to be solids here

Pole - the point at which a planets axis of rotation crosses the planet

Protostar - the result of the contraction of a nebula. A protostar is the point between a nebula and a main sequence star

Quark - general name given to any of six hypothetical particles believed to make up protons and neutrons

Radiation, Electromagnetic - energy waves resulting by the acceleration of an electric charge. They range from low frequency, low wavelength to high frequency, short wavelength. In order of increasing wavelength, the electromagnetic spectrum consists of radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays

Radiation Zone - the are of the sun between the core and the convection zone. Energy radiates through this zone from the core to the convection zone

Radius - the distance between the perimeter of a circle and the center of a circle. Sometimes, simply the distance between two points

Radius, Average - since ellipses have varying radii, the average of all the radii are used to perform calculations of Kepler's Third Law of Planetary Motion

Red Giant - a star in its dying phases. As the core of the star shrinks and heats up, the outer layers must expand and cool according to Newton's Third Law of Motion. These stars are very luminous but very cool

Rotation - the spin of a planet about its axis of rotation

Rs=2GM/C^2 - formula used to calculate the radius of the event horizon. The radius is equal to 2 times the gravitational constant (6.7e-11) times the mass of the black hole divided by the speed of light squared

Satellite - See moon

Season - the change in temperature of a parts of a planet due to the variation of the location where the suns rays are most direct

Singularity - a single point in space-time with an infinite density of matter. A singularity is believed to be at the center of black holes

Solar Flare - an explosion of cooler gases from a small area on the suns surface. Also associated with an intense outburst of radiation

Solar Mass (M) - the mass of our sun, approximately 1.99e30 kilograms

Solar System - the combination of a star, its surrounding planets, asteroids, comets, dust, etc.

Solar Wind - a stream of particles leaving the suns surface and traveling through space

Speed of Light - believed to be the speed limit in the universe. Nothing is supposed to be able to exceed the speed of light. It is also constant at 3e8 meters per second

Stable Equilibrium - when the nuclear reactions in a stars core are strong enough to withstand the crushing force of gravity

Star - a large celestial body, composed of highly condensed, hot gases. Energy in stars is produced by nuclear fusion it the stars core and is released in the form of electromagnetic radiation

Sublimate - the process in which a solid moves directly to the gaseous state, skipping over the form of a liquid

Sunspot - a dark, cooler area of the suns surface appearing as the result of changes in the suns magnetic field at that location

Supernova - the explosion of a high-mass star in its final stages before death

Synchronous Rotation - where the orbital period of a satellite is equal to its rotational period, resulting in the same "face" of the satellite pointing towards the planet

Theology - the study of religion and faith

Theory of Relativity - helped to show the unity between matter and energy, space and time, and gravity and acceleration.

Umbra - the conic-shaped shadow cast behind an object by the sun

Universe - all existing things, including the earth, the solar system, the galaxy, and everything therein regarded as a whole

Zodiac Sign - the 12 zodiacal constellations. Every person has a zodiac sign and it equated to the constellation that was in the direction of the sun at the time of your birth

Zodiacal - see ecliptic