astronomy 4

kipper belt

is a circumstantial disc in the Solar System beyond the planets, extending from the orbit of Neptune to approximately 50 AU from the Sun.

oort cloud

is an extended shell of icy objects that exist in the outermost reaches of the solar system.

retrograde motion

is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point.

dwarf planet

planetary-mass object that is neither a planet nor a natural satellite. That is, it is in direct orbit of the Sun, and is massive enough for its gravity to crush it into a hydrostatic equilibrium shape (usually a spheroid), but has not cleared the neighborhood of other material around its orbit.[1

mars

the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is often referred to as the "Red Planet"[13][14] because the iron oxide prevalent on its surface gives it a reddish appearance.[15] Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth.

heliopause

fluctuates and is influenced by a wind of interstellar gas caused by the Sun's motion through space. The orbits of all the major planets, including Earth's, lie well within the

europa

is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet. It is also the sixth-largest moon in the Solar System

saturn

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.[11][12] Although it has only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive

asteroid belt

the circumstantial 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.

neptune

the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune.[d] Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50×109 km).

enceladus

Enceladus en-CELL-ə-dəs; is the sixth-largest moon of Saturn. It is about 500 kilometers in diameter, about a tenth of that of Saturn's largest moon, Titan.

jupiter

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. Jupiter and Saturn are gas giants; the other two giant planets, Uranus and Neptune are ice giants.

titan

the largest moon of Saturn. It is the only moon known to have a dense atmosphere, and the only object in space other than Earth where clear evidence of stable bodies of surface liquid has been found.

venus

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. although its the second closest to the sun the atmosphere traps the heat and its not as hot as you would think.

uranus

the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have different bulk chemical composition from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the gas giants. Uranus's atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons.

mercury

the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 88 days is the shortest of all the planets in the Solar System. It is very hot because its the closest to the sun so no life can live on it.