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Planet Neptune: The Windy Ice Giant of the Solar System


Neptune is the eighth planet in order from the Sun. It is also known as the "Big Blue Planet" and is an ice giant, distinct from the rocky terrestrial planets like Earth. Neptune is about 3.9 times larger than Earth, and is the fourth-largest planet in our solar system. Neptune has a complex network of 14 moons, and a set of 5 distinct rings. Discover what the planet is made of, interesting facts and stats, our astrophotography attempts and observation tips, as well as information about space missions to the planet Neptune.


All you need to know about the planet Neptune


 

Neptune: The Mystic Giant


Neptune is the eighth planet from the Sun and lies in the outer reaches of our solar system, beyond Uranus. Neptune's atmosphere is mostly composed of hydrogen and helium, along with traces of other gases. Neptune is known for its icy blue appearance and intriguing atmospheric features. Neptune is the coldest planet in our solar system, with temperatures going as low as -224 degrees Celsius (-371 degrees Fahrenheit)! ❄️


Who was Neptune Named after?


Neptune - God of the Sea
God of the Sea

Neptune has a rich history of observation and naming, but was discovered much later than many other planets. The first recorded observation of Neptune was made by German astronomer Johann Gottfried Galle in 1846, following calculations by Urbain Le Verrier and John Couch Adams.


The name Neptune was chosen in honor of the Roman god of the sea, Neptune. This choice of name is in keeping with the tradition of naming planets after Roman deities. In Greek mythology, the equivalent deity is Poseidon, the god of the sea and waters, highlighting the planet's deep blue appearance.


 

Size and Mass


Size comparison between Earth and the planet Neptune
Earth vs Neptune - Real size

Neptune is a giant planet with a radius of about 15,299 miles (24,622 kilometers), making it almost four times larger than Earth. Its mass is 17 times the mass of Earth.


Despite its enormous size, Neptune's gravitational pull is only slightly stronger than that of Earth, at about 107% of Earth's gravity. This means that objects on Neptune would weigh slightly more than they do on our home planet. Neptune also has a magnetic field, though it is tilted relative to its rotational axis.


Neptune's atmosphere is a complex mix of hydrogen, helium, and traces of other gases. The extreme distance from the Sun means the temperatures on Neptune are extremely low, the average being -330 degrees Fahrenheit (-201 degrees Celsius).


 

Distance from the Sun


Neptune is located about 2.7 billion miles (4.35 billion kilometers) away from the Sun, placing it in the outer regions of the solar system. This far distance means Neptune receives much less sunlight and heat compared to inner planets.


This also makes Neptune difficult to see from Earth and not visible to the naked eye. It takes sunlight about 4 hours and 10 minutes to reach Neptune's surface from the Sun.


 

Time, Rotation, and Orbit


Let's board a shuttle to Neptune! If you were able to land and live on the giant planet, what would a day be like as a Neptunian?


Time


One day on Neptune is 16 hours and 6 minutes, making it one of the faster-rotating planets.


Rotation


The rotation on Neptune is, like most other planets, counter-clockwise. The rotation period on Neptune was studied when radio bursts were detected by the Voyager 2 spacecraft.


Unlike Mars and other planets, there is no known information about the surface speed of Neptune. The planet's surface features and movements are difficult to observe due to its thick, opaque atmosphere. For reference, the surface speed on Earth, at the equator, is 1,000 mph.


Orbit


Neptune orbits the Sun at an average distance of about 2.7 billion miles (4.35 billion kilometers), which is 30 times the distance between Earth and the Sun. It has a much more distant and elongated orbit compared to the inner planets. Neptune's orbital period, the time it takes to complete one orbit around the Sun, is almost 165 Earth years, making it one of the slowest-moving planets in our solar system. Neptune has circled the Sun only once since it was discovered in September 1846.


Neptune's orbit is elongated, resulting in huge variations in its distance from the Sun over the years. Because of that, Neptune's orbit is "crossed" by Pluto's orbit for 20 years every orbit cycle.


Neptune and Pluto's Orbits compared
Credit: Larry Wasserman

To summarize, the time and rotation on Neptune is not so different from what we have on Earth, 16 hours vs. 24 hours for one day. The length of a year though is much longer, with one year on Neptune being roughly 165 years on Earth!


 

Can You See Neptune with a Telescope?


Neptune is not visible with the naked eye, but it is possible to spot it with a telescope or even a pair of large astronomy binoculars.


What you will see through the telescope will depend on its size and quality. Do not expect to see much more than a fuzzy-looking star without details, although with the right equipment, you will have no problem seeing the planet's blue hue through the eyepiece. Despite the lack of features visible, Neptune's blue color is what makes it exciting to observe!



How to Observe Neptune with a Telescope


If you're looking for a telescope to observe your favorite planets, but don't know what to get, we have a few recommendations for you! It may be tempting to go for cheaper options, but you may end up wasting both your money and time. Please avoid telescopes sold at large retailers or grocery stores, as these cheap options are usually too good to be true and are made with low-quality materials.


Telescope to see Neptune and other planets

Dobsonian telescopes are the best telescopes to get for observing planets and the moon. They come in different sizes and prices and will last a lifetime!


For a complete beginner, an 8" Dobsonian (as seen here) is a good choice for larger planets like Jupiter but might not give you the best views of smaller-looking planets like Venus, Mars, or Neptune. If you don't mind the extra size and weight of the 10" and 12" versions, pick one of these instead!



Dobsonian telescopes are fantastic for visual observations, but if you attach a DSLR camera and pick up a few basic skills, you can capture cool photos of the moon and planets.


 

Can you take a picture of Planet Neptune from Earth?


Neptune is not a popular planet to photograph, and it makes sense! The planet is difficult to capture, small, doesn't show much detail, and is not easy to process. Beginner astrophotographers usually leave Neptune as one of their last planets to photograph, and it was also the case for us!


Can you take a picture of Neptune from Earth? Yes, you can, but don't expect a mind-blowing result! There are two ways to photograph planets through a telescope:

  1. Taking a single image using a DSLR or mirrorless camera attached to a telescope, which is the easiest option recommended for beginners

  2. Recording a video at a high frame rate and stacking the best frames into one image. This provides the best result but it is an advanced technique that requires a planetary camera and some processing skills


The picture below was taken with our ZWO ASI585MC camera and a Celestron C11 telescope from our backyard in Las Vegas. As you can see, it is blurry, noisy, and completely featureless... This was our very first attempt at capturing Neptune, so we hope our next will be better!


Picture of Neptune with a telescope

Would you like to learn astrophotography efficiently and at your own pace?


Gain lifetime access to a ton of astrophotography content by becoming a member of the Galactic Course. Whether you're a beginner or advanced, this course covers everything you need to know about astrophotography and offers much more.




 

Rings of Neptune



Rings of Neptune
Rings of Neptune. Credit: Roen Kelly

Gas giants often are home to ring systems, and Neptune is no exception. Its ring system, although faint, has unique characteristics, including its low density and a dark reddish hue. The five rings were named after key figures in the discovery and research of Neptune.




The five rings of Neptune, from closest to farthest:


  • Galle Ring

The innermost ring of Neptune. It i faint, wide, and spans about 2,000 kilometers (1,242 miles).


  • Le Verrier Ring

Much brighter than the Galle Ring, it measures just 113 kilometers (70.2 miles) in width.


  • Lassell Ring

A faint ring with a width of 4,000 kilometers (2,485 miles).


  • Arago Ring

Brighter but narrower ring at under 100 kilometers (62 miles).


  • Adams Ring

The outermost, thinnest, and most recently discovered ring. It measures only 35 kilometers (21.7 miles) in width. The Adams Ring is unique because it has a slight inclination and several bright arcs within it.

 

Planet Neptune History


Find out how Neptune was formed, what it is made of, if life is sustainable on the planet and more.


First close-up picture of Neptune - NASA - August 31, 1989
First close-up picture of Neptune - NASA - August 31, 1989

Formation and Age


Neptune, like other planets in our Solar System, formed 4.6 billion years ago during the early stages of the Solar System's evolution. It emerged from the dust and gas that had condensed into a proto-planetary disk surrounding the young Sun. This process of planetary formation involved the gradual accretion of materials within the disk, leading to the creation of Neptune as we know it today.


Can Neptune Support Life?


The conditions on Neptune make it simply impossible for any life to form, not even for microbial life that survives in extreme environments. The planet's atmosphere is composed of hydrogen and helium, with extreme cold and high-pressure conditions. You also can't land and walk on Neptune because it does not have a solid surface, but it is instead full of turbulent gasses and extreme winds. And if you somehow were to reach the surface, the temperatures there plunge to -330 degrees Fahrenheit (-201 degrees Celsius), far below freezing.


The winds on Neptune can reach up to 1,500 miles per hour (2,400 kilometers per hour), making it one of the windiest planets in the Solar System.


Check out our other posts to discover if life is sustainable on other planets, like Jupiter.


 

Composition and Structure


What is Neptune Made of?


Composition of Neptune
Credit: NASA

Neptune's composition is made up of 80% hydrogen and 19% helium, with a few different other gases like methane and ammonia present in its atmosphere. Unlike terrestrial planets, Neptune lacks a solid surface.


The center of Neptune includes a dense, rocky core, with an unknown composition. Surrounding the core is a vast layer of various gases that include dense icy regions.



The atmosphere has four layers, the innermost one being the lower troposphere, followed by the stratosphere, the thermosphere, and the exosphere. Neptune's exosphere is one of the coldest places in our solar system. Neptune does not have a solid surface, and we cannot peak through the clouds of ice and gases to see what the planet looks like behind all this matter.


Neptune Sunrise and Atmosphere
Sunrise on Neptune rendition. Credit: Sirgerg on Deviantart

 

What is the Weather Like on Planet Neptune?



Neptune is the second coldest planet in the solar system, right behind Uranus.


Neptune's intense winds blow at near-supersonic speeds of up to 1,324 miles per hour (2,160 kilometers), breaking the sound barrier. These winds. five times more powerful than the strongest winds on Earth, move westward in the opposite direction to the planet's rotation.


Below you can see pictures of Neptune taken by the Keck observatory over a period of almost thirty years. It shows the cycle of the storms, with the infrared clouds visible and moving a lot over time. You can see how stormy the planet was between 2005 and 2017, compared to how quiet it became starting in 2019.


Imke de Pater, Erandi Chavez, Erin Redwing (UC Berkeley) / W. M. Keck Observatory
Credit: Imke de Pater, Erandi Chavez, Erin Redwing (UC Berkeley) / W. M. Keck Observatory

Neptune has an axial tilt of 28.32 degrees, which is similar to both Earth (23.4 degrees) and Mars (25 degrees). Neptune has about the same seasonal changes as our own planet, although each season lasts for about 40 years.


Learn more about the planets in order from the sun.


 

The Great Dark Spot of Neptune


For about half of its time, Neptune seems to get large dark spots that last for months or years before disappearing.


Great Dark Spot on Neptune - 1989
Great Dark Spot on Neptune - 1989

In 1989, NASA's Voyager 2 probe discovered the first Great Dark Spot on Neptune, and designated it as "GDS-89".


This storm eventually faded away, as confirmed by an image taken by the Hubble Space Telescope several years later.



These dark spots on Neptune are similar to Jupiter's famous Great Red Spot, but do not last!


The origin, movement, and disappearance of these dark spots are still unknown since their discovery in 1989.




 

NASA Space Telescope Images of Neptune


Both the Hubble Space Telescope and the James Webb Space Telescope were able to photograph Neptune. Let's take a look at what result each telescope was able to get!


Neptune by the Hubble Space Telescope


Taken on September 7 and released two months later on November 18, 2021, the image shown below is one of the few pictures of Neptune taken by the Hubble Space Telescope.


This was photographed using three different filters. Blue was mapped to the F467M filter, Green to F547M, and Red to the F657N filter.


As you can see, the image is not as impressive as some other images taken by different telescopes, and that's because the Hubble Space Telescope excels at deep sky imaging rather than planetary. This shot was done in order to track the progress of Neptune's dark spot, which is still visible here.


Neptune by NASA and the Hubble Space Telescope

 

Neptune by the James Webb Space Telescope



Neptune by the James Webb Telescope and NASA

The images you see here were released on September 21, 2022, and show an incredible view of Neptune... with its rings!


One of the images show the full field of view, with Neptune and its moons, including the bright Triton. The other image is a close-up view of the planet without annotation.


This was shot with the JWST's NIRCam instrument which is a near-infrared camera. This is why the planet does not look blue as it should, due to the colors being false. The rings, although already captured back in 1989 with Voyager 2, look incredibly clear in this version 30 years later, and several moons can be seen orbiting the planet.


Click the image to see the full article from NASA!

Neptune by the James Webb Telescope and NASA

 

Missions to Neptune


Unlike several other planets, Neptune was only visited by a single spacecraft, and that was more than thirty years ago! No other missions have been sent to Neptune since then, mostly due to how far the planet is compared to our closer neighbors.


Voyager 2 (1961-1984)


Voyager 2
Voyager 2 spacecraft

The Voyager 2 spacecraft completed its main mission when it reached Saturn, but it was then decided that it would keep going to both Neptune and Uranus before going interstellar. This extended mission was called the Voyager Neptune Interstellar Mission. Voyager 2's first images of Neptune were navigation shots in May 1988, and the actual observation image started on June 5, 1989. The observations stopped on October 2, about a month and a half after officially reaching the Neptunian system.



 

The Moons of Neptune


Voyager 2 discovered several moons when flying by Neptune, while a few others were discovered from Earth years before and years after the Voyager 2 mission. In total, Neptune has 14 moons of different shapes and sizes:



Naiad

Discovery: September 1989

Discovered by: Voyager 2

Shape: Oval

Size: Small

Other: Will crash into Neptune at some point


Thalassa

Discovery: August 1989

Discovered by: Voyager 2

Shape: Thin oval

Size: Small


Despina

Discovery: July 1989

Discovered by: Voyager 2

Shape: Irregular

Size: Small

Other: It is located inside Neptune's ring system


Galatea

Discovery: July 1989

Discovered by: Voyager 2

Shape: Irregular

Size: Small


Larissa

Discovery: 1981 bu confirmed in July 1989

Discovered by: H. Reitsema, W. Hubbard, L. Lebofsky, and D. Tholen but confirmed by Voyager 2

Shape: Oval

Size: Small

Other: Will crash into Neptune at some point


Hippocamp

Discovery: July 1st, 2013 using old Hubble Space Telescope images

Discovered by: Mark Showalter

Shape: Irregular

Size: Tiny (20 miles / 34 km in diameter) - Smallest moon of Neptune


Proteus

Discovery: 1989

Discovered by: Voyager 2

Shape: Mostly round

Size: Large

Other: One of the darkest moons in the Solar System


The inner moons of Neptune
The inner moons of Neptune

Halimede

Discovery: August 14, 2022

Discovered by: Matthew J. Holman, John J. Kavelaars, Tommy Grav, Wesley C. Fraser, and Dan Milisavljevic

Shape: Irregular

Size: Tiny, missed by Voyager 2


Laomedeia

Discovery: August 13, 2022

Discovered by: Matthew J. Holman, John J. Kavelaars, Tommy Grav, Wesley C. Fraser, and Dan Milisavljevic

Shape: Irregular

Size: Small


Nereid

Discovery: May 1st, 1949

Discovered by: Gerard P. Kuiper

Shape: Irregular

Size: Large

Other: Has the most eccentric orbit of any moon in the Solar System


Neso

Discovery: 2022

Discovered by: Matthew J. Holman, John J. Kavelaars, Tommy Grav, Wesley C. Fraser, and Dan Milisavljevic

Shape: Irregular

Size: Small

Other: Most distant known moon of any planet


Psamathe

Discovery: August 29, 2003

Discovered by: Scott S. Sheppard, David C. Jewitt and Jan T. Kleyna

Shape: Irregular

Size: Small


Sao

Discovery: August 14, 2002

Discovered by: Tommy Grav, Matthew J. Holman, John J. Kavelaars, Wesley C. Fraser, and Dan Milisavljevic

Shape: Irregular

Size: Tiny


Triton

Discovery: October 10, 1846

Discovered by: William Lassell

Shape: Round

Size: Large - Largest moon of Neptune

Other: Discovered 17 days after Neptune was discovered


Triton by Voyager 2
Triton by Voyager 2

 

Final Thoughts and Summary of the Planet Neptune


Neptune is the eighth planet from the Sun and is known for its blue color and far distance. Its small and featureless appearance makes Neptune a rarely photographed target for amateur astrophotographers, but the planet can be appreciated visually with the right eyepiece.


Venus picture
  • Type: Ice giant

  • Name Origin: Roman god of the sea

  • Discovered in: September 23, 1846

  • Radius: Approximately 15,299 miles (24,622 km)

  • Temperatures: Extremely cold, averaging around -201°C

  • Distance from Sun: 4.35 billion km on average

  • Day: 16 hours and 6 minutes

  • Orbit: 165 Earth years

  • Natural Satellites (moons): 14

  • Light speed from Sun: 4 hours and 10 minutes


We hope you learned more about Neptune using this guide! We will write a tutorial post in the future that will be dedicated to the astrophotography aspect of Neptune and how to get a great image of this blue ice giant!


In the meantime, check out our post explaining the Solar System planets in order.


Clear Skies,

Galactic Hunter

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