Pluto moons

Pluto Moons – Collateral Members of Water Ice Society

Moonlight – From a Different Point of View

Grey Pluto moons rising!

We love to raise our head up.. We assume that’s why you are here!

And when you look to the sky, observing our moon gliding towards thousands of stars, slightly brightening our way.. But what if you asked for more? What about having 4pcs more moons in the sky where one of them invading most of the view?


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Meanwhile; you can navigate to the bottom of this page for “Frequently Asked Questions” about Pluto moons.

Icy Moons of Pluto – Characteristics

Many people believe we do not have enough knowledge to comment about evolution of planets and planet systems.. Dzzt, they are wrong!

Scientists did not only evaluate how the planets in Solar System formed: But also we have basic knowledge about how our Solar System, other star systems, galaxies and even the universe is born! No extra courage needed to understand a standard planet and the facts about its moons!

How Were Pluto Moons Formed?

As explained on Pluto System article, we have general knowledge about how Pluto and Pluto moons were formed. Let’s skip the part about formation of Pluto (as we’ve stated the details on Pluto facts article too) and jump into formation facts about Pluto moons.

Pluto Moons
Pluto and Pluto moons, captured by Hubble Space Telescope, Credits: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team

Scientists believe there has been a huge collision between Pluto (let’s say the “Beta Version” of Pluto) and another big planet. The consequence was formation of Charon.

Try hitting two rocks with high speed. What will happen? Same incident happened right after the Grand Pluto Collision: Together with Charon and Pluto’s primitive and miserable versions, residues spread all over the space.

One possibility is, some of the smaller Pluto moons were prototypes of those residues. Another possibility is that some of the residues collided with each other.

See the images of moons Kerberos and Hydra, you’ll easily confirm that it makes perfect sense!

Pluto Moons – Orbit and Rotation

Pluto System is like a family with 5 kids. There’s a big kid, Charon. Charon behaves more like an adult. At the same time never turns her face away from mother Pluto where the mother is addicted to her biggest girl.

Rest of the kids try to seem nice to mother Pluto but they are overactive and uncontrollable babies.

You’ll get our point:

An illustration of Pluto Moons orbiting gravitational center (barycenter) of system, together with Pluto. Credit: NASA/JHUAPL/SwRI/Mark Showalter. Video produced by AGU

Let’s see what happens there:

First of all we have to state that all objects in Pluto System have almost circular orbits around barycenter. In addition, orbital inclinations of all are very close to zero.

Pluto is the closest object to systems’ gravitational center and drawing the narrowest orbital circle.

Our next buddy is Charon. Take a quick glance to the white dots on Pluto and Charon, which represents their faces: Yes, they look to each other all the time. Charon and Pluto are mutually tidally locked to each other.

Rest of the Pluto moons seem to orbit nicely as well. That’s true. However their white dots are not exactly the real faces of these little monsters.
Those tiny moons Hydra, Nix, Kerberos and Styx have a chaotic axial rotation and it’s not easy to estimate what their next move will be.

An illustration by ESA, illustrating the rotation of moon Nix. This illustration is also valid for Hydra, Kerberos and Styx. Credit: NASA, ESA, M. Showalter (SETI Inst.), G. Bacon (STScI)

Detailed numbers about orbital and axial rotations will seperately be noted for each Pluto moon on Pluto Moons – With Numbers chapter.

Pluto Moons – Shape and Size Comparison

Above stated chaotic rotation of smaller moons is a direct result of their shape and size. In addition, amorphous shape of those is a direct result of their size. When a rocky object is big enough, rotation on its own axis will eventually force the object become spherical. When it is not, than it becomes atypical!

Look at Charon and Pluto: That wasn’t the case for them!

Pluto and Charon
Pluto and Charon. Source: NASA

Let’s assign “x” for the size of moon Styx. That roughly makes Kerberos 2x, Nix 8x, Hydra 9x, Charon 200.000x and Pluto 1.300.000x where our Earth becomes 220.000.000x.

If the Earth was in size of a blue whale, than Pluto would be a tiny lizard in comparison. That makes Charon a small mosquito and other tiny moons microscobic little creatures.

Pluto Moons – Surface Composition

Majority of Charon surface is made of water ice in powder form. And the remaining materials are NH3 (ammonia) compunds.

Researchers are sure the surfaces of Hydra and Nix include water ice. When it comes to Kerberos and Styx; although the researches could not verify 100%, they believe those two moons should have similar surface formations.

Pluto Moons
Pluto Moons in scale. Source: NASA

All Pluto moons are dominated with grey color. However scientists observed red-brown formations on Charon‘s north pole and Nix‘s big crater area. Those formations are anticipated to be tholin layers, and the researchers are quite sure that’s true especially for Charon.

Tholins are organic molecules formed after interaction of solar radiation with methane. Since no methane molecules detected on Charon or Nix, researchers believe methane molecules evaporating from Pluto surface travel all the way to those moons and sticks on a cold surface. Hence the tholin formation process initiates.

Pluto Moons – Surface Features

Since the small Pluto moons are “primitive rocks” in general, it’s hard to mention surface features other than minor rugged areas and crater impact zones.

However when it comes to Charon, we can not summarize its surface features only with crater impacts. It’s so complex that, Charon surface is mapped by New Horizons Team members!

Charon has a complex tectonicsm and surface regeneration background. Together with extension of its surface, scientists believe there used to be an ocean beneath Charon surface which is frozen twice in the past. What is more, signs and consequences of cryovolcanism are easily anticipated.

Charon Mountain
A Charon mountain sitting in a moat. Source: NASA

As a result of that turbulent history, Charon has various surface features: Mountain ranges, wide plain regions, scarped areas and so on.

Life on Pluto Moons

Distance between neighourhoods in the universe are extremely far from each other. What is more, the way life and habitat evolved on our world has too many demands.

Above conditions make things remarkably harder than it looks regarding our search for an alien society.

With our current knowledge about life, we can easily eliminate smaller Pluto moons in this search.. They are completely vulnerable to hazards of empty space and do not seem to have any protective mechanisms to hide primitive life.

However Charon had a showy feature in the past: An underworld ocean! Bad news is, researchers believe that last time the ocean is frozen at least 700 million years ago. Which means, even if any kind of creatures found a way to evolve and live in such a protected ocean; they should have found a way to live on after their world died.. Well, that does not seem very likely!

Once upon a time, Charon had an underground ocean.. Source: NASA

Wait, do not despair! There might be another icy object with an ocean nearby: Scientists’ calculations reveal there’s a big chance that Pluto can include a hidden ocean beyond her icy crust!

Pluto Moons in Astrology

You know what we think about astrology.. But let’s repeat once more:

Any of Pluto moons, their size, distance to Earth, gravitational effect or any kind of their attributes have nothing to do with your horoscope, daily life or anything else about your mood. This is common for any planet, moon or cosmic object in the universe you can think of.

Astrology means fairy tales.

Astronomy relies on facts; on a thing we named in last few centuries: The Science

Pluto Moons – With Numbers

We leave some basic, encyclopedic information for all Pluto moons here:


  • Age: 4.5billion years (approximate)
  • Orbiting Period: 6.39 days
  • Rotation Period: 6.39 days
  • Mass: 1.6×10²¹ kg
  • Mean density: 1.7 g/cm3
  • Radius: 606km
  • Distance to Pluto System Barycenter: 17.536km
Moon Charon. Source: NASA
  • Atmosphere: None
  • Magnetosphere: None
  • Temperature: −220 °C
  • Dominant Surface Material: Water Ice
  • Discovery Date: 22 June 1978
  • Discoverer: James Christy


  • Age: 4.5billion years (approximate)
  • Orbiting Period: 38.2 days
  • Rotation Period: 0.43 days (this can vary in time)
  • Mass: (4.8±4.2)×1016 kg
  • Mean density: 2.13 g/cm3
  • Dimenisons: 50.9×36.1×30.9 km
  • Distance to Pluto System Barycenter: 64.738km
Moon Hydra. Source: NASA
  • Atmosphere: None
  • Magnetosphere: None
  • Temperature: −250°C
  • Dominant Surface Material: Water Ice
  • Discovery Date: 15 June 2005
  • Discoverer: Hal A. Weaver, Alan Stern, Marc William Buie & New Horizons Team


  • Age: 4.5billion years (approximate)
  • Orbiting Period: 24.8 days
  • Rotation Period: 1.8 days (this can vary in time)
  • Mass: (4.5±4)×1016 kg
  • Mean density: 1.37 g/cm3
  • Dimenisons: 49.8 x 33.2 x 31.1 km
  • Distance to Pluto System Barycenter: 48.694km
Moon Nix. Source: NASA
  • Atmosphere: None
  • Magnetosphere: None
  • Temperature: −240 to 218°C
  • Dominant Surface Material: Water Ice
  • Discovery Date: 15 June 2005
  • Discoverer: Hal A. Weaver, Alan Stern, Marc William Buie & New Horizons Team


  • Age: 4.5billion years (approximate)
  • Orbiting Period: 32.2 days
  • Rotation Period: 5.31 days (this can vary in time)
  • Mass: 1.65×1016 kg
  • Dimenisons: 19 x 10 x 9 km
  • Distance to Pluto System Barycenter: 57.783km
Moon Kerberos. Source: NASA
  • Atmosphere: None
  • Magnetosphere: None
  • Dominant Surface Material: Water Ice
  • Discovery Date: 28 June 2011
  • Discoverer: Mark Showalter & New Horizons Team


  • Age: 4.5billion years (approximate)
  • Orbiting Period: 20.2 days
  • Rotation Period: 3.24 days (this can vary in time)
  • Mass: 7.5×1015 kg
  • Dimenisons: 16 x 9 x 8 km
  • Distance to Pluto System Barycenter: 42.656km
Moon Styx. Source: NASA
  • Atmosphere: None
  • Magnetosphere: None
  • Dominant Surface Material: Water Ice
  • Discovery Date: 26 June 2012
  • Discoverer: Mark Showalter & New Horizons Team

Frequently Asked Questions

In case you finished reading above, you already have knowledge about below. Don’t waste your time and skip to another article!

  • Question: Does Pluto Have Moons?
  • Answer: Yes! We hope you’ve read this article till this line and do not seek an answer for this question.. Dude, that’s the name of our article!
  • Question: How many moons does Pluto have?
  • Answer: 5pcs.
  • Question: What are the Pluto Moon names?
  • Answer: Names of Pluto moons, from big to small: Charon, Hydra, Nix, Kerberos and Styx.
  • Question: What is the size of Pluto moons?
  • Answer: Charon: 606km in radius, Hydra: 50.9×36.1×30.9 km , Nix: 49.8 x 33.2 x 31.1 km , Kerberos: 19 x 10 x 9 km, Styx: 16 x 9 x 8 km.
  • Question: Can you explain Pluto moons’ orbits?
  • Answer: Sure! All Pluto moons (together with Pluto itself) orbit the systems’ gravitational center with almost circular orbits as shown on below image.
Pluto moons
Orbits of Pluto moons. Source: NASA
  • Question: Which one is the biggest moon of Pluto?
  • Answer: Charon.
  • Question: Discovery years of Pluto Moons?
  • Answer: Charon: 1978, Hydra: 2005, Nix: 2005, Kerberos: 2011, Styx: 2012.
  • Question: What are Pluto moons made of?
  • Answer: They are all dominated by water ice on the surface. Scientists believe the inner cores include silicates, oxides and sulfides.
  • Question: What is the temperature on Pluto moons?
  • Answer: -200 to -270ºC.
  • Question: Do they have atmospheres?
    Answer: NO.
  • Question: Is there life on Pluto moons?
  • Answer: No, as far as we know.
  • Question: What are other quick facts about Pluto Moons?
  • Answer: Charon is the the only moon of Pluto being a sphere and having planet-like features. Rest of the moons are not spherical, have chaotic axial rotations and primitive rocks. All moons have water ice and wide crater areas on their surfaces.
  • Question: Why does the shape of Pluto moons vary?
  • Answer: Planets and moons are the residues of Star System formations. They are formed and shaped by collisions. According to calculations and given enough time, a body needs to be bigger than 500km in diameter to be able to settle to a hydrostatic equilibrium and be spherical. Smaller bodies can not maintain this and they can not be spherical. While Charon and Pluto have diameters bigger than 1.000km, widest dimension of Hydra (biggest of rest of Pluto Moons) is about 50km.


  • We aim to build a proper Pluto encyclopedia and your contributions are highly appreciated!
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