The exact number depends on the individual planet, and the exact shape and eccentricity of its orbit.
The one general statement that can be made for every planet is that when it's farthest from the sun,
it's moving at the slowest speed relative to the sun of any point in its entire orbit.
Aphelion
The path that planets take around the sun is called it's orbit. The gravitation pull of the sun keeps each planet in it's orbit. Each planets orbit varies in the time it takes to make one trip around the sun.
Pluto used to be the outermost planet, except that sometimes it became Neptune because Pluto's elliptical orbit is far from circular. From 1979 to 1999 Neptune was the farthest planet from the Sun and remains the farthest from the Sun today, because Pluto us no longer defined as a planet.
The Earth is the 6th farthest planet from the Sun. Neptune is the farthest.
Within our Solar System, Pluto was until it was dubbed a dwarf planet. The current farthest planet is Neptune. Since Pluto has an orbit so eccentric that it is sometimes inside the orbit of Neptune, the identity of the "outermost planet" was previously time-dependent.
The speed of a planet is fastest when it is closest to the sun in its orbit (option 1) and slowest when it is farthest from the sun (option 2). This is because of the gravitational pull of the sun, which accelerates the planet as it gets closer and decelerates it as it moves away.
Neptune. Because it was the farthest planet from the sun. So its orbit's length is long.
Planet Neptune takes the most time to orbit the sun, as it is the farthest away.
The farthest planet from the sun used to be Pluto. Pluto is now considered to be a dwarf planet, not a planet. When Pluto was a planet, its orbit would sometimes take it closer to the sun than Neptune, making the Neptune the farthest planet from the sun for that period of time.
An orbit. the farthest known orbit in our solar system is the Oort belt, in the farthest reaches of our sun's gravitational field.
Aphelion
The maximum distance from the sun in a planet's orbit is called its aphelion. This point is farthest from the sun, as opposed to the perihelion, which is its closest point.
Neptune has been the farthest planet from the sun for 20 years due to Pluto [the dwarf planet] passing through it's orbit . Since the reclassification of Pluto as a dwarf planet rather than a planet, in 2006, Neptune will remain the farthest planet, regardless of Pluto's position in it's orbit.
nearest to the sun
Neptune is not always the farthest planet from the sun. Pluto's elliptical orbit means that it can be closer to the sun than Neptune for periods of time.
Pluto is the farthest planet from the sun . It has the longest orbit.
perihelion