Neptune

102 × Earth 17.1

This is the mass of the planet in septillion (1 followed by 24 zeros) kilograms or sextillion (1 followed by 21 zeros) tons. Strictly speaking tons are measures of weight, not mass, but are used here to represent the mass of one ton of material under Earth gravity.

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49,528 × Earth 3.88

The diameter of the planet at the equator, the distance through the center of the planet from one point on the equator to the opposite side, in kilometers or miles.

NASA notes ↗

1638 × Earth 0.297

The average density (mass divided by volume) of the whole planet (not including the atmosphere for the terrestrial planets) in kilograms per cubic meter or pounds per cubic foot. Strictly speaking pounds are measures of weight, not mass, but are used here to represent the mass of one pound of material under Earth gravity.

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NASA notes ↗

11.0 × Earth 1.12

The gravitational acceleration on the surface at the equator in meters per second squared or feet per second squared, including the effects of rotation. For the gas giant planets the gravity is given at the 1 bar pressure level in the atmosphere. The gravity on Earth is designated as 1 "G", so the Earth ratio fact sheets gives the gravity of the other planets in G's.

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23.5 × Earth 2.10

Initial velocity, in kilometers per second or miles per second, needed at the surface (at the 1 bar pressure level for the gas giants) to escape the body's gravitational pull, ignoring atmospheric drag.

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16.1 × Earth 0.673

This is the time it takes for the planet to complete one rotation relative to the fixed background stars (not relative to the Sun) in hours. Negative numbers indicate retrograde (backwards relative to the Earth) rotation.

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16.1 × Earth 0.671

The average time in hours for the Sun to move from the noon position in the sky at a point on the equator back to the same position.

Not drawn.

NASA notes ↗

4515.0 × Earth 30.18

This is the average distance from the planet to the Sun in millions of kilometers or millions of miles, also known as the semi-major axis. All planets have orbits which are elliptical, not perfectly circular, so there is a point in the orbit at which the planet is closest to the Sun, the perihelion, and a point furthest from the Sun, the aphelion. The average distance from the Sun is midway between these two values. The average distance from the Earth to the Sun is defined as 1 Astronomical Unit (AU), so the ratio table gives this distance in AU. * For the Moon, the average distance from the Earth is given.

NASA notes ↗

4471.1 × Earth 30.40

The closest and furthest points in a planet's orbit about the Sun, see "Distance from Sun" above. * For the Moon, the closest and furthest points to Earth are given, known as the "Perigee" and "Apogee" respectively.

NASA notes ↗

4558.9 × Earth 29.97

The closest and furthest points in a planet's orbit about the Sun, see "Distance from Sun" above. * For the Moon, the closest and furthest points to Earth are given, known as the "Perigee" and "Apogee" respectively.

NASA notes ↗

59,800 × Earth 163.7

This is the time in Earth days for a planet to orbit the Sun from one vernal equinox to the next. Also known as the tropical orbit period, this is equal to a year on Earth. * For the Moon, the sidereal orbit period, the time to orbit once relative to the fixed background stars, is given. The time from full Moon to full Moon, or synodic period, is 29.53 days. For Pluto, the tropical orbit period is not well known, the sidereal orbit period is used.

NASA notes ↗

5.4 × Earth 0.182

The average velocity or speed of the planet as it orbits the Sun, in kilometers per second or miles per second. * For the Moon, the average velocity around the Earth is given.

Drawn: today’s position and the direction of motion. The arrow is a symbol; its length is not the speed.

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1.8

The angle in degrees at which a planets orbit around the Sun is tilted relative to the ecliptic plane. The ecliptic plane is defined as the plane containing the Earth's orbit, so the Earth's inclination is 0.

NASA notes ↗

0.010 × Earth 0.677

This is a measure of how far a planet's orbit about the Sun (or the Moon's orbit about the Earth) is from being circular. The larger the eccentricity, the more elongated is the orbit, an eccentricity of 0 means the orbit is a perfect circle. There are no units for eccentricity.

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28.3 × Earth 1.21

The angle in degrees the axis of a planet (the imaginary line running through the center of the planet from the north to south poles) is tilted relative to a line perpendicular to the planet's orbit around the Sun, north pole defined by right hand rule. *Venus rotates in a retrograde direction, opposite the other planets, so the tilt is almost 180 degrees, it is considered to be spinning with its "top", or north pole pointing "downward" (southward). Uranus rotates almost on its side relative to the orbit, Pluto is pointing slightly "down". The ratios with Earth refer to the axis without reference to north or south.

NASA notes ↗

-200

This is the average temperature over the whole planet's surface (or for the gas giants at the one bar level) in degrees C (Celsius or Centigrade) or degrees F (Fahrenheit). For Mercury and the Moon, for example, this is an average over the sunlit (very hot) and dark (very cold) hemispheres and so is not representative of any given region on the planet, and most of the surface is quite different from this average value. As with the Earth, there will tend to be variations in temperature from the equator to the poles, from the day to night sides, and seasonal changes on most of the planets.

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Unknown*

This is the atmospheric pressure (the weight of the atmosphere per unit area) at the surface of the planet in bars or atmospheres. *The surfaces of Jupiter, Saturn, Uranus, and Neptune are deep in the atmosphere and the location and pressures are not known.

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16

This gives the number of IAU officially confirmed moons orbiting the planet. New moons are still being discovered.

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Yes

This tells whether a planet has a set of rings around it, Saturn being the most obvious example.

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Yes

This tells whether the planet has a measurable large-scale magnetic field. Mars and the Moon have localized regional magnetic fields but no global field.

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