How Far is Neptune from Earth? Facts About Neptune

In this article we are going to answer the question, how far is Neptune from Earth? Neptune is 2.7 billion miles (4.3 billion km) away from Earth when it is at its closest and 2.9 billion miles (4.7 billion km) away at its farthest. The distance varies because both planets are in constant motion on their respective orbits.

How far is Neptune from the Sun?

Neptune is 2.795 billion miles (4.498 billion km) away from the sun. That’s 30 Astronomical Units (AU) away from the sun – an AU is a distance between Earth and the Sun.

Due to its elliptical orbit, sometimes it is either closer or farther from the sun than that. It is 2.771 billion miles (4.460 billion miles) at its closest and 2.819 billion miles (4.537 billion kilometers) at its farthest from the sun.

This ice giant is the most distant planet from the sun. That label belonged to Pluto until it was relegated from planetary status. Nevertheless, for 20 years, Pluto’s orbit cuts into the Neptunian orbit during which the sun is closer to Pluto than to Neptune.

Neptune takes 165 years (Earth years) to complete one trip around the sun. Since it was discovered in 1846, it completed its first orbit in 2011.

How long does it take light to travel to Neptune?

Sunlight takes approximately 4 hours to reach Neptune. Light takes 4 hours and 5 minutes to travel from Neptune to Earth. Reflected light from Neptune takes longer because it is weaker than sunlight.

What are the diameter and circumference of Neptune?

Neptune’s diameter is four times bigger than Earths. Its diameter is 30,598 miles (49,244 kilometers) and its circumference is 96,685 miles (155,600 kilometers). It is only a bit smaller than the other ice giant, Uranus.

How long would it take to travel to Neptune?

It is hard to tell exactly how long it would take you to reach Neptune because there are many factors to consider. You cannot just take the shortest route there because you need to orbit around some planets or moons for a gravitational boost to save on fuel.

Only two spacecraft have paid Neptune a visit; Voyager 2. It was launched in 1977 and it reached there 12 years later in 1989. New Horizons reached Neptune in 8 years and 8 months. To be fair, New Horizons was the fastest spacecraft ever launched and it was targeting Pluto.

What would you find when you get to Neptune?

Neptune has a blue tint that is partly caused by Methane absorbing red light. You cannot see Neptune with the naked eye at night. You have to observe it using a telescope.

Neptune was discovered through mathematical prediction when Urbain Le Verrier, a French astronomer, found anomalies in the orbit of Uranus and hypothesized that there must be another body causing them. Neptune was later first observed with a telescope through the mathematical calculation to confirm that indeed, there was a planet.

The Atmosphere:

The atmosphere of Neptune has 80% Hydrogen, 18.5% Helium, and small amounts of Methane. The core is made of Magnesium Silicate and Iron. It is covered by a mantle made up of water and frozen methane and ammonia. It does not support any known life forms.

The Seasons:

There are seasons on Neptune because the axis is tilted at 28 degrees relative to the orbit’s plane. This tilt is very close to Earth’s tilt of 23.5 degrees. However, since it takes Neptune more than 160 years to orbit the sun, each season lasts over 40 years. Neptunian days are shorter than Earth days because Neptune takes 16 hours to rotate about its axis.

Neptune is very cold because it is far from the sun. In fact, it is called an ice giant because it is more icy than gassy (unlike Saturn and Jupiter). Nevertheless, it is not as cold as Uranus because it emits heat from its interior while Uranus doesn’t.

The average temperature is -253 degrees Fahrenheit (214 degrees Celsius). Seasonal changes also affect temperatures on Neptune. For example, the side facing the sun, although very far, still heats up relative to the rest of the planet.

The Windiest Planet:

Neptunian winds are the fastest of any planet in the Solar System. Clouds can move at speeds of up to 1,500 miles per hour (2,400 kilometers per hour). The most fascinating thing is that it achieves that without the help of the sun warming up its atmosphere.

Voyager 2 picked up on a giant spot (“Great Dark Spot”) the size of Earth that was probably a massive 750 miles per hour (1,200 kilometers per hour) storm moving west. However, when scientists searched for it later using the Hubble telescope, it was nowhere to be seen. This phenomenon was recurrent with other storms. They concluded that storms form and disappear on Neptune.

Oddly Tilted Magnetic Field:

The Neptunian magnetic field is skewed 47 degrees away from the axis of rotation. This odd phenomenon was observed on Uranus but scientists thought it was just caused by the heavily tilted Uranian axis. Neptune proved them wrong but they are yet to conclusively determine the course of this anomaly. Neptune’s field is 27 times stronger than that of Earth.

How many moons does Neptune have?

Neptune has 14 moons (13 confirmed). Neptune’s outer moons have some of the longest orbits in the solar system. The largest and most significant one is known as Triton.

Unlike other irregularly shaped Neptunian moons, Triton is spherical. It is the only major moon in the entire solar system whose orbit goes in the opposite direction (in retrograde) to the planet’s direction of rotation. Triton’s surface is extremely cold – reaching as low as -391 F (-235 C).

Neptune’s Rings

The six rings of Neptune are rather faint and somewhat irregular. They are named after the scientists who were involved in the discovery of Neptune and its satellites.
Naming them from the innermost to the outermost, they are:

Galle;
Le Verrier;
Lassell;
Arago;
and the Adams Ring.

The Le Verrier and the Adams rings are relatively bright. The rest are faint and hardly visible.

Is there water on Neptune?

Scientists believe that water is one of the components of the mantle. It is mixed in with frozen methane and ammonia.

How much would you weigh on Neptune?

Neptune has a mass 17 times that of Earth. Neptune’s corresponding gravitational strength is 110% that of Earth. If you weigh 100 pounds on Earth, the scale would read 110 pounds on Neptune.

Man’s Missions to Neptune

Only Voyager 2 and New Horizons have ever ventured near Neptune. Voyager 2 flew by and helped us discover the rings and six moons. New Horizons was further away from Neptune but it still revealed new features. The rest of what we know about Neptune has been observed using telescopes.

Additional Readings

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