Asteroids
Any of the small rocky celestial bodies found especially between the orbits of Mars and Jupiter
Axis tilt
Axial tilt is the inclination angle of a planet's rotational axis in relation to a perpendicular to its orbital plane. It is also called axial inclination or obliquity. The axial tilt is expressed as the angle made by the planet's axis and a line drawn through the planet's center perpendicular to the orbital plane.
Big Bang
The dominant scientific theory about the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.
Colonization
Permanent communities built and inhabited off the Earth.
Comets
A celestial body that appears as a fuzzy head usually surrounding a bright nucleus, that has a usually highly eccentric orbit, that consists primarily of ice and dust, and that often develops one or more long tails when near the sun
Constellations
Any of 88 arbitrary configurations of stars or an area of the celestial sphere covering one of these configurations
Copernicus
A mathematician and astronomer who proposed that the sun was stationary in the center of the universe and the earth revolved around it. Disturbed by the failure of Ptolemy's geocentric model of the universe to follow Aristotle's requirement for the uniform circular motion of all celestial bodies and determined to eliminate Ptolemy's equant, an imaginary point around which the bodies seemed to follow that requirement, Copernicus decided that he could achieve his goal only through a heliocentric model. He thereby created a concept of a universe in which the distances of the planets from the sun bore a direct relationship to the size of their orbits. At the time Copernicus's heliocentric idea was very controversial; nevertheless, it was the start of a change in the way the world was viewed, and Copernicus came to be seen as the initiator of the Scientific Revolution.
Galaxies
Any of the very large groups of stars and associated matter that are found throughout the universe. The Milky Way galaxy includes our sun and solar system as well as myriads of stars.
Kepler
A German mathematician and astronomer who discovered that the Earth and planets travel about the sun in elliptical orbits. He gave three fundamental laws of planetary motion.(interactive java animation)
- Kepler's First Law: a planet orbits the Sun in an ellipse with the Sun at one focus.
- Kepler's Second Law: a ray directed from the Sun to a planet sweeps out equal areas in equal times.
- Kepler's Third Law: the square of the period of a planet's orbit is proportional to the cube of that planet's semimajor axis; the constant of proportionality is the same for all planets.
Moons
A natural satellite of a planet
(The moon: the earth's natural satellite that shines by the sun's reflected light, revolves about the earth from west to east in about 29 days with reference to the sun or about 27 days with reference to the stars, and has a diameter of 2160 miles (3475 kilometers), a mean distance from the earth of about 238,900 miles (384,400 kilometers), and a mass about one eightieth that of the earth)
Nebulae
A nebula is an interstellar cloud of dust and gas. Originally nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy is sometimes referred to as the Andromeda Nebula).
Planets
1: Any of the large bodies that revolve around the sun in the solar system
2: a similar body associated with another star
Probes
Any instrument-carrying device sent from Earth to study another celestial body, to penetrate and send back information, for example measurements of the conditions in space.
Ptolemy
Claudius Ptolemaeus was a Greek philosopher who created a geocentric theory of the solar system in which the planets and Sun orbitted the Earth in the order of: Mercury, Venus, Mars, Jupiter, Saturn. This system became known as the Ptolemaic system and predicted the positions of the planets accurately enough for naked-eye observations.
Revolution
1: the action by a celestial body of going round in an orbit or elliptical course; also : apparent movement of such a body round the earth
2: the time taken by a celestial body to make a complete round in its orbit
Rotation
The movement of a celestial body about its axis, as if on a pivot.
Satellites
1: a celestial body orbiting another of larger size
2: a manufactured object or vehicle intended to orbit the earth, the moon, or another celestial body
Solar and lunar eclipses
1: the total or partial obscuring of one celestial body by anoth
2: the passing into the shadow of a celestial body
- Lunar eclipse: an eclipse in which the full moon passes partially or wholly through the umbra of the earth's shadow
- Solar eclipse: an eclipse of the sun by the moon
Spectroscopes
Devices used for separating light into component colours for analysis.
Star clusters/types
A group of stars that are held together by their mutual gravitational attraction. In the Milky Way, there are two different types of star clusters:
- Open (or "galactic") Cluster: are usually about the same age, having being born together from a collapsing nebula.
- Globular Cluster: a very old, large, dense cluster of stars, bound by gravity. Many form spherical clouds around galaxies. Our galaxy is surrounded by at least 130 globular clusters.
Sun
The star about which the Earth and other planets revolve.
Telescopes
Usually tubular optical instruments for viewing distant objects by means of the refraction of light rays through a lens or the reflection of light rays by a concave mirror
Terraforming
The process of modifying a planet, moon or other body to a make it more habitable for humans, for example, altering the atmosphere, temperature or ecology.
Sources:
Guide to the Universe Astronomy Dictionary
Classroom Strategies for Teaching Science Definitions
