Celestial planets

What makes a planet a celestial body?

A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.

What is a planet in astronomy?

A more modern definition can be found in the Merriam-Webster dictionary which defines a planet as "any of the large bodies that revolve around the Sun in the solar system." In 2006, the International Astronomical Union (IAU) - a group of astronomers that names objects in our solar system - agreed on their own definition of the word "planet."

Which planets have a ring system?

The planets, in order of their distance outward from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Four planets—Jupiter through Neptune—have ring systems, and all but Mercury and Venus have one or more moons.

Which planets have a substantial atmosphere?

Titan (Saturn’s largest moon) is the only moon in the solar system known to have a substantial atmosphere. Above: I photograph the planet Saturn using an 11″ telescope in my backyard. Uranus is the seventh planet from the Sun and like Venus, rotates in the opposite direction as the other planets.

Which planets are outward from the Sun?

Outward from the Sun, which is represented to scale by the yellow segment at the extreme left, are the four rocky terrestrial planets (Mercury, Venus, Earth, and Mars), the four hydrogen-rich giant planets (Jupiter, Saturn, Uranus, and Neptune), and icy, comparatively tiny Pluto.

What are the first 4 planets from the Sun?

The first four planets from the Sun are Mercury, Venus, Earth, and Mars. These inner planets also are known as terrestrial planets because they have solid surfaces. Mercury is the smallest planet in our solar system, and the nearest to the Sun. Venus is the second planet from the Sun, and Earth's closest planetary neighbor.