Planets P3

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.

Phases

A distinct period or stage in a process of change or forming part of something's development.

Eclipse

A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the Sun, Earth, and Moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle.

Meteorite

A meteorite is a fragment of rock or iron from outer space, usually a meteoroid or asteroid, which survives passage through the atmosphere as a meteor to impact the surface of the Earth. Meteorites are believed to originate in the asteroid belt between the planets of Mars and Jupiter.

Meteoroid

A meteoroid is a small rocky or metallic body travelling through outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects.

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.

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.

Terrestrial Planets

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.

Astronomical Unit

ASTRONOMICAL UNIT (AU) 1 AU = 149,597,870.700 kilometers (or 149,597,870,700 meters) Definition: An Astronomical Unit is the mean distance between the Earth and the Sun.

Retrograde Rotation

All eight planets in the Solar System orbit the Sun in the direction that the Sun is rotating, which is counterclockwise when viewed from above the Sun's north pole. Six of the planets also rotate about their axis in this same direction. The exceptions—the planets with retrograde rotation—are Venus and Uranus.

Satellite

An artificial body placed in orbit around the earth or moon or another planet in order to collect information or for communication.

Ceres

Ceres is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter. Its diameter is approximately 945 kilometers, making it the largest of the minor planets within the orbit of Neptune.

Earth

Earth is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only astronomical object known to harbor life.

Jupiter

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined.

Mars

Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury.

Mercury

Mercury is the smallest planet in the Solar System and the one closest to the Sun, with an orbital period of about 88 Earth days, which is much faster than any other planet in the Solar System.

Neptune

Neptune is the eighth and farthest known planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Among the giant planets in the Solar System, Neptune is the most dense.

Pluto

Pluto was known as the smallest planet in the solar system and the ninth planet from the sun. Today, Pluto is called a "dwarf planet." A dwarf planet orbits the sun just like other planets, but it is smaller. A dwarf planet is so small it cannot clear other objects out of its path.

Saturn

Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth.

Asteroid Belt

The asteroid belt is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets.

Gas Giants

Their compositions are mostly gases, such as hydrogen, and small amounts of rocky material (mostly at their cores). The four gas giants in our solar system are Jupiter, Saturn, Uranus, and Neptune.

Uranus

Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System.

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has the longest rotation period of any planet in the Solar System and rotates in the opposite direction to most other planets. It has no natural satellite.

Prograde Rotation

prograde. (prō'grād') Having a rotational or orbital movement that is the same as most bodies within a celestial system. In our solar system, prograde movement for both rotating and orbiting bodies is in a counterclockwise direction when viewed from a vantage point above the Earth's north pole. Compare retrograde.