Haumea facts for kids
Low-resolution Hubble Space Telescope image of Haumea and its two moons, Hiʻiaka (top) and Namaka (bottom)
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| Discovery | |
|---|---|
| Discovered by | |
| Discovery date |
|
| Designations | |
| MPC designation | (136108) Haumea |
|
Named after
|
Haumea |
| (136108) Haumea 2003 EL61 |
|
|
|
| Adjectives | Haumean |
| Orbital characteristics | |
| Epoch 17 December 2020 (JD 2459200.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 65 years and 291 days |
| Earliest precovery date | 22 March 1955 |
| Aphelion | 51.585 AU (7.7170 Tm) |
| Perihelion | 34.647 AU (5.1831 Tm) |
| 43.116 AU (6.4501 Tm) | |
| Eccentricity | 0.19642 |
| 283.12 yr | |
|
Average orbital speed
|
4.53 km/s |
| 218.205° | |
| Inclination | 28.2137° |
| 122.167° | |
| 239.041° | |
| Known satellites | 2 (Hiʻiaka and Namaka) |
| Physical characteristics | |
| Dimensions | 2,122+174 −144 × 1,688+10 −14 × 1,036+36 −38 km |
|
Mean diameter
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1,544+40 −38 km |
| ≈ 8.14×106 km2 | |
| Volume | ≈ 1.98×109 km3 |
| Mass | (3.952±0.011)×1021 kg |
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Mean density
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2.050+0.157 −0.152 g/cm3 |
|
Sidereal rotation period
|
3.915341±0.000005 h |
| ≈ 126° | |
| ≈ 0.66 | |
| Temperature | < 50 K |
Haumea is an unusual dwarf planet that travels in the cold outer edges of our Solar System. It circles the Sun far beyond the orbit of Neptune. Haumea has a very weird shape because it looks like a stretched football or an egg. It spins faster than almost any other large world in our cosmic neighborhood. A single day on Haumea lasts less than four hours. It also has two small moons, a dark red spot, and its own thin ring system.
Astronomers classify Haumea as a trans-Neptunian object because its path lies beyond Neptune. It is also the third-largest known trans-Neptunian object, right behind Pluto and Eris. Even though it is very far away, scientists have learned many exciting facts about it. Haumea is covered in shiny, frozen water ice, making it gleam brightly in deep space.
Contents
Discovering the Weird World of Haumea
Who Found Haumea in the Night Sky?
The discovery of Haumea involves two different teams of sky watchers. A team led by astronomer Mike Brown studied pictures taken at the Palomar Observatory. They spotted the object on December 28, 2004, from pictures taken earlier that year. His partners included Chad Trujillo and David L. Rabinowitz. They watched it secretly for many months so they could learn more about its movement.
At the same time, another group was working in Spain. Astronomer José Luis Ortiz Moreno and his team worked at the Sierra Nevada Observatory. They found the object in July 2005 while checking older photographs taken in March 2003. Ortiz sent an email to the Minor Planet Center to announce the find first. Both teams had found the same icy world, creating a puzzle over who should get credit.
The International Astronomical Union stepped in to make an official choice. They decided to list the Spanish observatory as the location of the discovery. However, they chose the name suggested by Brown's team from the California Institute of Technology. Before it got an official name, Brown's group called the object "Santa" because they found it around Christmas time. The object was also given the code number 136108 and the temporary label 2003 EL61.
How Haumea Got Its Hawaiian Name
Scientists follow rules made by the International Astronomical Union when naming newly found worlds. Objects in the distant Kuiper belt are often named after creator figures from world myths. The American astronomers suggested naming the planet after Haumea, the Hawaiian goddess of nature and childbirth. This honored the island of Hawaiʻi, where huge telescopes like the W. M. Keck Observatory operate on Mauna Kea.
In Hawaiian legends, many children sprang from different parts of Haumea's body. Astronomers thought this name was perfect because Haumea has icy moons that broke off from it during a giant crash. The two moons were named Hiʻiaka and Namaka, who are daughters of the goddess. A special planetary symbol was even made for Haumea, showing a simple drawing for woman and birth.
Journey Around the Sun
The Long Path in Outer Space
Haumea takes an extraordinarily long time to travel around the Sun. Its orbital period is about 284 Earth years. When it comes closest to the Sun, at its perihelion, it is about 35 astronomical units away. One astronomical unit is the distance from Earth to the Sun. At its farthest point, called aphelion, it travels over 51 astronomical units away.
Haumea passed its farthest point from the Sun in 1992. It is slowly moving inward and will reach its closest point around the year 2133. Haumea has a tilted path with an orbital inclination of 28 degrees. Most major planets stay flat on the main disc of the Solar System, called the ecliptic. Because Haumea is tilted, astronomers had to look far above the common path to find it.
Haumea also has an oval path, which astronomers describe as eccentricity. A special gravitational dance called the Kozai mechanism slowly changes its orbit over millions of years. Even though it is billions of miles away, Haumea has a bright visual magnitude of 17.3. It is the third-brightest body in the Kuiper belt after Pluto and Makemake, making it visible through large backyard telescopes.
A Gravitational Dance with Neptune
Haumea has a special relationship with the giant planet Neptune. It is considered a resonant object because of how their paths interact. For every seven times Neptune circles the Sun, Haumea travels around roughly twelve times. This is called a weak 7:12 orbital resonance.
This gentle gravitational balance changes back and forth over millions of years. As the planet travels, its path wobbles through a motion called libration. Scientists study this motion using a rotating frame to understand how Neptune shapes the outer solar system. Over billions of years, gravity might push Haumea into a completely different path, sending it into deep space.
The Super Fast Spin of Haumea
A Day Shorter Than Four Hours
One of the coolest facts about Haumea is how quickly it spins on its axis of rotation. It completes a full turn in just 3.91 hours. This is faster than any other known large round object in our entire Solar System. If Earth spun that quickly, breakfast, lunch, and dinner would all happen within a few hours.
Astronomers discovered this wild spin by watching the planet's light curve. As Haumea turns, its brightness changes dramatically in a regular pattern. When the wide side faces Earth, it looks brighter because more ice reflects sunlight. When the pointed end faces us, it looks dimmer. This regular change showed scientists that the fast spin causes the brightness shifts.
Why Haumea Looks Like a Football
Gravity usually pulls large worlds into neat, round balls called spheres. When a planet reaches this balance, scientists say it has achieved hydrostatic equilibrium. However, Haumea spins so fast that strong outward forces stretch its middle into an equatorial bulge. This extreme force deformed Haumea into a three-dimensional oval known as a Jacobi ellipsoid.
If Haumea spun just a little bit faster, the outward pull would tear it apart. It would split into two separate lumps like a dumbbell. Instead, it remains held together, looking like an enormous cosmic egg. Astronomers watch it almost edge-on from Earth, giving us a great view of its spinning motion.
Size, Structure, and Ice Surface
How Big Is Haumea?
Measuring the size of distant objects in space is a tricky job for astronomers. Telescopes see them as tiny points of light rather than clear discs. Scientists look at their optical magnitude, distance, and albedo, which means how much light their surface reflects. Shiny objects can look large even if they are small, while dark objects look tiny.
In January 2017, astronomers got lucky when Haumea passed directly in front of a distant star. This event is called a stellar occultation. By timing how long the star was hidden from different observatories, scientists measured Haumea with great accuracy. Along its longest side, it measures more than 2,100 kilometers across, which is nearly as wide as Pluto. From top to bottom, it measures only about 1,000 kilometers.
Haumea has a mass of around 4.0 × 1021 kilograms, calculated using Kepler's laws of planetary motion. That makes it about one-third the mass of Pluto and much smaller than Earth's Moon. Its overall density is about 2.0 grams per cubic centimeter. This tells scientists that Haumea is mostly heavy stone inside, rather than just soft ice.
What Is Haumea Made Of?
Underneath its frozen crust, Haumea has a large core made of silicate rocks. Scientists believe the core contains minerals like kaolinite, olivine, and pyroxene. These heavy rocks settled into the middle through a natural process called planetary differentiation.
Around this rocky core lies an icy mantle. The ice layer is about 70 kilometers thick near the poles and up to 170 kilometers thick near the equator. Unlike typical Kuiper belt objects that have huge amounts of ice, Haumea has a thinner coat. Scientists think a colossal collision long ago knocked away much of its original icy shell.
A Sparkling Surface of Pure Ice
Haumea has a brilliant surface that shines almost as brightly as fresh snow. When astronomers studied its light with the Gemini Observatory and the W. M. Keck Observatory, they found clean water ice. The light showed clear signs of crystalline ice, which normally forms in warm conditions.
This crystalline ice is a big mystery. Space in the Kuiper belt is freezing cold, with temperatures dropping below 50 kelvin. At those low temperatures, water usually forms messy amorphous ice. Also, high-energy particles called cosmic rays constantly hit the surface, which should destroy crystalline patterns. Some unknown process might be refreshing the surface with brand-new ice.
The surface of Haumea also has a fascinating dark red patch. Astronomers discovered this spot in 2009 by watching small changes in color. This red area stands out brightly against the clean white frost. It might be an ancient impact crater where space rocks churned up minerals and carbon-rich chemicals called tholin.
The Discovery of Haumea's Ring
During the 2017 star-blocking event, astronomers noticed something unexpected. The star's light blinked out briefly before Haumea reached it, and blinked again after Haumea passed by. This proved that Haumea has its own ring system. It became the first dwarf planet and the first trans-Neptunian object known to possess rings.
The ring sits about 2,287 kilometers from the center of the planet and is roughly 70 kilometers wide. It lies well within Haumea's Roche limit, which is the danger zone where gravity stops moons from sticking together. The ring particles circle the planet in a steady orbit, tilted slightly compared to the equator.
Scientists study the ring using orbital dynamics to learn how it survives. The ring particles complete one trip around the planet for every three times Haumea spins. This balance keeps the particles safe from being thrown outward into space.
Two Tiny Moons: Hiʻiaka and Namaka
Haumea has two known natural moons, discovered in 2005 using the Keck telescope in Hawaii. Both moons were named after daughters of the Hawaiian goddess Haumea. They travel around the dwarf planet in chilly, stable paths.
The larger and outer moon is named Hiʻiaka. It measures about 310 to 370 kilometers across and takes 49 days to orbit Haumea. Hiʻiaka is covered in pure water ice, just like Haumea itself. Its surface reflects lots of sunlight, making it much brighter than most captured asteroids.
The smaller, inner moon is named Namaka. It is about half the size of Hiʻiaka and has only one-tenth the mass. Namaka circles Haumea in just 18 days on a tilted path. The gravity of the bigger moon tugs on Namaka, causing its path to shift through a process called apsidal precession.
Between 2008 and 2011, Namaka passed directly in front of Haumea as seen from Earth. These events are called occultations. Observers at places like the Pico dos Dias Observatory in Brazil watched the moons cross the planet. These rare alignments gave scientists valuable clues about the size and shape of the entire system.
| Moon Name | Diameter (km) | Distance from Haumea (km) | Time to Orbit (days) | Discovery Year |
|---|---|---|---|---|
| Namaka | ≈ 150 | 25,657 | 18 | 2005 |
| Hiʻiaka | ≈ 310–370 | 49,880 | 49 | 2005 |
The Broken Family in Deep Space
Haumea is not traveling alone; it leads a group of space rocks called a collisional family. A collisional family is a group of objects that share similar paths and surfaces because they were once part of the same parent body. This was the very first family of its kind discovered in the outer solar system.
Billions of years ago, a massive object likely smashed into Haumea at high speed. This collision knocked away much of Haumea's outer ice crust and spun it up like a top. The shattered pieces became Haumea's two moons and several smaller icy worlds. Known members of this family include objects with names like (55636) 2002 TX300 and (24835) 1995 SM55.
Astronomers believe this crash must have happened more than a billion years ago. Today, the Kuiper belt is mostly empty space, so collisions are extremely rare. The smash probably occurred when the solar system was very young and crowded, in a region called the scattered disc.
Missions and Exploration
Because Haumea is located so far away, no spacecraft has visited it up close yet. However, the robotic probe New Horizons took distant pictures of Haumea between 2007 and 2020. Even from huge distances, the probe gathered helpful data about how Haumea's surface reflects light.
Scientists have planned possible future space missions to explore Haumea. A spacecraft could use the gravity of giant planets like Jupiter to slingshot itself toward the outer solar system. Traveling that far takes a long time, often requiring more than 15 years of flight. A robot visitor would give us our very first clear pictures of Haumea's strange egg shape, its gleaming ring, and its icy moons.
Related Pages
- 20000 Varuna – another fast-spinning, elongated space rock in the outer Solar System
- 208996 Achlys – a distant icy world with a fast spin
- Astronomical naming conventions – how stars, planets, and moons get their names
- Dwarf planet – small worlds that circle the Sun
- Kuiper belt – the icy ring of worlds beyond Neptune
Images for kids
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The orbital path of Haumea moving in resonance with Neptune.
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A chart tracking the gravitational balance between Haumea and Neptune over time.
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Haumea captured as a faint dot of light by the New Horizons spacecraft.
See also
In Spanish: Haumea (planeta enano) para niños
