In order to be declared a planet, a celestial body must meet the following qualifications: It must orbit the sun, it must maintain a nearly spherical shape and have the necessary mass for self-gravity so that it does not succumb to rigid body forces, and it must clear the neighborhood around its orbit. All recognized planets in the solar system meet this definition.Know More
This definition of "planet" was most recently modified in August 2006 and is clearly defined in the International Astronomical Union Resolution 5. As result, Pluto is no longer considered a planet, and there are only eight recognized planets in the solar system. Unlike other planets, Pluto does not clear the neighborhood around its orbit, according to UCLA. Therefore, it is now classified as a "dwarf planet."
The criteria for a dwarf planet are similar to planets: It must orbit the sun; it must maintain a nearly spherical shape and have the necessary mass for self-gravity so that it does not succumb to rigid body forces; it does not clear the neighborhood around its orbit; and it is not a satellite.
In contrast to the other eight planets, Pluto is embedded in a swarm of similar celestial bodies and has many neighbors orbiting nearby. As a result, Pluto is now considered part of the trans-Neptunian population.Learn More
The eight described planets all orbit the Sun at different distances; Mercury is the closest planet to the sun, followed by Venus, then Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The distances of the planets are normally measured in kilometers, because scientists use metric measurements. However, scientists also use a unit called an “astronomical unit,” which is equal to the distance between Earth and the sun.Full Answer >
Beginning with the planet closest to the Sun and moving outward, the order of the planets is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Before its reclassification as a dwarf planet by the International Astronomical Union in 2006, Pluto was considered the ninth and most distant planet.Full Answer >
The surface temperatures of the solar system's planets are dependent on how close each planet is to the sun. Planets that have atmospheres are better able to retain heat from the sun, affecting the planet's surface temperature.Full Answer >
The inner planets of the solar system are all relatively close to the sun. They are also all relatively similar to each other in size, mass, density and other physical properties. Unlike the outer planets, the inner planets are small, dense and warm.Full Answer >