Unit 4: The Planets and Other Objects

Neptune (features)

Smaller but denser ice giant. It is the furthest from the sun and is the only planet whose location was first predicted based on math and was then located using a telescope.

Short period comet

A comet that orbits the Sun in less than 200 years that originates from the scattered disk.

Long term comet

A comet with an orbital period of greater than 200 years that originates from the Oort Cloud.

Planetary rings

A disk of material that circles a planet and consist of orbiting particles of rock or ices in a thin plane. Found around all four of the outer planets.

Comet

A loose collection of ice and dust that orbits the sun, typically in a long, narrow orbit. Contains a nucleus which when heated by the sun, ablates to form the Cona, and two tails, one dust tail and one charged particle tail.

Meteorite

A meteoroid that passes through the atmosphere and hits Earth's surface.

Kuiper Belt

A region of the solar system that is just beyond the orbit of Neptune and that contains small bodies made mostly of ice, with some asteroids and dwarf planets (including Pluto) as well.

Oort Cloud

A spherical region that surrounds the solar system, that extends from the Kuiper Belt to almost halfway to the nearest star, and that contains billions of comets. Long term comets originate from this region.

Meteor

A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere.

Cryovolcano

A volcano that spews out water, ice, carbon dioxide, or methane rather than molten rock. Common on several moons in the outer planets and may be an indicator for conditions that could support life.

Dwarf Planet

An object that orbits the sun and is spherical, but has not cleared the area of its orbit.

Asteroid

Any of numerous small celestial bodies composed of rock and metal that move around the sun. Mainly found between the orbits of Mars and Jupiter, but may also be found in the outer regions of the solar system. May be a single solid piece or a "clump" of many smaller objects.

Mercury (features)

Closest to Sun, most dense planet with a very large core of molten iron, smallest orbit of only 88 days, with a single "day" lasting 57 earth days.

Venus (features)

Has a core and mantle likely similar to Earth's. Extremely thick atmosphere with high levels of Carbon Dioxide making it the hottest planet and with high pressure over 90 times that of Earth. Rains sulfuric acid. Has a day (243 earth days) that is longer than it's year (224 earth days). May have recently been "repaved" by a massive upwelling of lava through super volcanoes spread across the surface.

Mars (features)

High levels of iron rust in the soil make the surface appear red. Has the largest mountain and the largest canyon in the solar system. Has frozen water in the ice caps and had liquid water on the surface in the past. Has the most volcanoes of any planet. Only inner planet besides earth that has moons (2).

Ice Giant Planets

Large planets with atmospheres of water vapor, ammonia and methane, with thick frozen mantles composed of ices of the same materials. Cores may be composed of rock of frozen ices. Unique pressure and chemistry in the mantles may cause the atmospheres to "rain" liquid diamonds.

Gas Giant Planets

Large, gaseous planets that have ring systems, many moons, and lack solid surfaces, instead the "surface" is composed of liquid metallic hydrogen, with a thick atmosphere of gaseous hydrogen and helium. They may or may not have a rocky/metallic core.

Uranus (features)

Largest of the ice giants. It is tilted 90 degrees on its axis, likely from a massive collision in it's past. Has at least 27 moons, some of which may have liquid water beneath the surface. Can not be easily seen with the naked eye and was first officially discovered using a telescope.

Saturn (features)

Second largest planet and one of the gas giants. Least dense of all the planets and could "float" in water. Has the largest ring system composed of frozen water and dust and dozens of moons.

Scattered Disk

The disk-shaped region beyond the Kuiper Belt that contains many small bodies made of ice and rock. Their highly elliptical orbits may reach perihelion as low as 30 AU and aphelion as high as 100 AU. This region is where Short Period Comets originate from.

Jupiter (features)

The largest planet and one of the gas giants. The only planet to emit more heat than it absorbs from the sun. Atmosphere has active weather systems with bands and zones and a great red spot that is a hurricane which has been visible for more than 300 years. Has 63 moons with at least two moons which may have liquid water beneath their surface.

Terrestrial Planets

The name given to the four inner planets: Mercury, Venus, Earth, and Mars. They all have iron cores with rocky outer layers and were geologically active in the past or still are. They have few to no moons, no rings, a short period (year) and a slower rotation (day)

Meteoroid

a small body moving in the solar system that would become a meteor if it entered the earth's atmosphere.

Asteroid belt

the region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found. It is thought that this may be a location where a protoplanet formed, but was pulled apart by the gravity of Jupiter, however it's total mass would be less than that of Earth's moon.