Space Definitions Flashcards
Orbit
The Curved path of a planet it around the sun.
Solar system
The circular pattern of all of the planets in a solar system
Galaxy
a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.
Universe
all existing matter and space considered as a whole; the cosmos. The universe is believed to be at least 10 billion light years in diameter and contains a vast number of galaxies; it has been expanding since its creation in the Big Bang about 13 billion years ago.
Satellite
an artificial body placed in orbit around the earth or moon or another planet in order to collect information or for communication.
Impact crater
a crater on a planet or moon caused by the impact of a meteorite or other object, typically circular with a raised rim.
Rotation
the action of rotating around an axis or center.
Revolution
an instance of revolving.
Season
each of the four divisions of the year (spring, summer, autumn, and winter) marked by particular weather patterns and daylight hours, resulting from the earth’s changing position with regard to the sun.
Equinox
the time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length
Solstice
either of the two times in the year, the summer solstice and the winter solstice, when the sun reaches its highest or lowest point in the sky at noon, marked by the longest and shortest days.
Mare
the female of a horse or other equine animal.
Eclipse
an obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of illumination.
Umbra
the fully shaded inner region of a shadow cast by an opaque object, especially the area on the earth or moon experiencing the total phase of an eclipse.
Penumbra
the partially shaded outer region of the shadow cast by an opaque object.
Astronomical unit (AU)
a unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun.
Ellipse
a regular oval shape, traced by a point moving in a plane so that the sum of its distances from two other points (the foci) is constant, or resulting when a cone is cut by an oblique plane which does not intersect the base.
Terrestrial planet
A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun, i.e. Mercury, Venus, Earth, and Mars.
Gas giant
a large planet of relatively low density consisting predominantly of hydrogen and helium, such as Jupiter, Saturn, Uranus, or Neptune.
Asteroid
a small rocky body orbiting the sun. Large numbers of these, ranging in size from nearly 600 miles (1,000 km) across (Ceres) to dust particles, are found (as the asteroid belt ) especially between the orbits of Mars and Jupiter, though some have more eccentric orbits, and a few pass close to the earth or enter the atmosphere as meteors.
Comet
a celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles pointing away from the sun.
Meteor
a small body of matter from outer space that enters the earth’s atmosphere, becoming incandescent as a result of friction and appearing as a streak of light.
Meteorite
a meteor that survives its passage through the earth’s atmosphere such that part of it strikes the ground. More than 90 percent of meteorites are of rock, while the remainder consist wholly or partly of iron and nickel.
Geocentric
having or representing the earth as the center, as in former astronomical systems.
