Namaka (moon)
Michael E. Brown spotted a faint smudge of light in high-resolution images taken by the Keck II telescope on the 1st of March, the 28th of May, and the 30th of June 2005. This object was much dimmer than its brighter sibling moon Hiiaka, which had been found earlier that January. The Central Bureau of Astronomical Telegrams announced the discovery to the world on the 1st of December 2005. Brown initially nicknamed the new find Blitzen after one of Santa Claus's reindeer. He used Christmas-themed names for the entire Haumea system during that holiday season. The International Astronomical Union officially named the satellite Namaka on the 17th of September 2008. This name honors a water spirit from Hawaiian mythology who is a daughter of the goddess Haumea. Brown's team proposed these names in September 2006 to honor the location where they made their discoveries at Mauna Kea in Hawaii.
Namaka circles the dwarf planet Haumea every 18.3 days at an average distance of roughly 25,000 kilometers. Its path follows a highly elliptical orbit with an eccentricity of about 0.22. The orbital plane tilts roughly 13 degrees relative to both Haumea's equator and the orbit of its larger sister moon Hiiaka. Gravitational tugs from Hiiaka constantly pull on Namaka while the elongated shape of Haumea creates a variable gravitational field. These forces cause Namaka's orbit to shift over time with changing eccentricity and inclination. Simulations suggest the moons share an 8:3 mean-motion resonance where Hiiaka completes three orbits for every eight completed by Namaka. This resonance likely transferred initial orbital energy from Hiiaka to Namaka over hundreds of millions of years. The exact duration of this resonant state remains uncertain among astronomers today.
Visible light and thermal infrared observations place Namaka's diameter between 170 and 260 kilometers. If it measures around 210 kilometers across, it would be half the size of Hiiaka. Scientists estimate its mass at approximately 4.9 times 10 to the 19th kilograms. This makes Namaka ten times less massive than Hiiaka and only 0.03 percent as heavy as Haumea itself. Such low density suggests a highly porous interior similar to other small trans-Neptunian objects. The surface reflects fresh water ice with an albedo ranging from 50 to 80 percent. Only one stellar occultation has been recorded so far on the 16th of March 2025 when Namaka passed in front of a distant background star. Future measurements of such events could refine our understanding of its true dimensions.
Hubble Space Telescope images from 2008 showed brightness fluctuations of 0.3 magnitudes indicating an elongated shape. Later observations from 2009 and 2010 failed to detect any significant periodic fluctuation in that same brightness data. These conflicting results suggest either a highly tilted rotation axis or a slow spin lasting longer than one day. Tidal forces from nearby Haumea should have slowed the moon's rotation over time. If the spin remains slow, the eccentric orbit causes multiple spin-orbit resonances to induce chaotic behavior. Simulations predict axial tilt and rotation period will vary unpredictably over years much like Saturn's moon Hyperion. Confirming this chaotic state requires long spans of high-resolution observation that astronomers are still gathering today.
Namaka and Hiiaka likely formed 4.4 billion years ago following a massive collision between two large Kuiper belt objects. This event occurred roughly 77 to 82 million years after the Solar System first came into existence. A 2022 study led by Jessica Noviello suggests Haumea continued differentiating after the initial impact. Centrifugal forces eventually grew so strong that icy surface material ejected into orbit around the dwarf planet. About 3 percent of Haumea's initial mass and 14 percent of its angular momentum were lost during this rotational fission process. The accretion of surrounding material was gentle enough to allow Namaka to form with low density. Some moons escaped the system while others remained as Namaka, Hiiaka, and a ring of debris.
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Common questions
When was the moon Namaka discovered by Michael E. Brown?
Michael E. Brown spotted the faint smudge of light on the 1st of March, the 28th of May, and the 30th of June 2005 using images from the Keck II telescope. The Central Bureau of Astronomical Telegrams announced the discovery to the world on the 1st of December 2005.
Why did the International Astronomical Union name the satellite Namaka in 2008?
The International Astronomical Union officially named the satellite Namaka on the 17th of September 2008 to honor a water spirit from Hawaiian mythology who is a daughter of the goddess Haumea. Brown's team proposed these names in September 2006 to honor the location where they made their discoveries at Mauna Kea in Hawaii.
How long does it take for the moon Namaka to orbit the dwarf planet Haumea?
Namaka circles the dwarf planet Haumea every 18.3 days at an average distance of roughly 25,000 kilometers. Its path follows a highly elliptical orbit with an eccentricity of about 0.22 that tilts roughly 13 degrees relative to both Haumea's equator and the orbit of its larger sister moon Hiiaka.
What are the physical dimensions and mass of the moon Namaka?
Visible light and thermal infrared observations place Namaka's diameter between 170 and 260 kilometers while scientists estimate its mass at approximately 4.9 times 10 to the 19th kilograms. This makes Namaka ten times less massive than Hiiaka and only 0.03 percent as heavy as Haumea itself.
When did the collision that created the moon Namaka occur?
Namaka and Hiiaka likely formed 4.4 billion years ago following a massive collision between two large Kuiper belt objects. This event occurred roughly 77 to 82 million years after the Solar System first came into existence when centrifugal forces ejected icy surface material into orbit around the dwarf planet.