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Moon of Haumea
Namaka
The small icy inner moon of egg-shaped Haumea, named after a Hawaiian water spirit
Key facts
- Diameter
- About 93.2 miles / 150 km (uncertain by about 50 km either way)
- Distance from Haumea
- About 16,000 miles / 25,700 km (semi-major axis)
- One orbit
- About 18.28 Earth days
- Orbit shape
- Noticeably stretched (eccentricity about 0.22 to 0.25)
- Mass
- About 1.2 × 10^18 kg, roughly 0.05% of Haumea
- Discovered
- 30 June 2005, Michael E. Brown and the Keck Observatory team, Keck II telescope (announced 1 December 2005)
- Named after
- Namaka, a Hawaiian water spirit and daughter of Haumea (named 17 September 2008)
- Surface
- Mostly fresh water ice
- Brightness
- Far fainter than Haumea; too small and distant to see clearly
- Parent's moons
- Haumea has 2 known moons, Namaka and Hi'iaka, as of August 2026
- Visited by
- No spacecraft
About Namaka
Namaka is a small moon. It goes round a dwarf planet. The dwarf planet is called Haumea. Haumea is shaped like an egg. It spins very fast. Namaka is Haumea's little moon. Haumea has a big moon too. It is much bigger than Namaka. Namaka is very far from the Sun. It is dark and cold there. Namaka is made of ice. The ice is like frozen water. Namaka was found by a big telescope. Its name comes from Hawaii. Namaka is a water spirit. No spaceship has been there yet. Maybe you will send one!
Namaka is the smaller of the two moons of Haumea. Haumea is a dwarf planet far beyond Neptune in the Kuiper Belt. It is shaped like a squashed rugby ball and spins once every 4 hours. Namaka is about 150 kilometres across, though its exact size is uncertain.
It is so small that its gravity may not pull it into a perfect sphere. Namaka takes about 18 days to complete one orbit around Haumea. It orbits at a distance of roughly 25,700 kilometres from the dwarf planet. Its orbit is stretched, not circular, and is tilted at a steep angle.
Astronomers think the tug of Haumea's odd shape and the big moon Hi'iaka disturb it. Hi'iaka is the outer moon and is more than twice as wide as Namaka. Namaka's surface is made mostly of fresh water ice, so it is bright for its size. Even so, it is far fainter than Haumea when seen from Earth.
Michael Brown's team spotted Namaka on 30 June 2005 using the Keck II telescope in Hawaii. The moon was named in 2008 after Namaka, a water spirit in Hawaiian stories. In the myths, Namaka is one of the daughters of the goddess Haumea. No spacecraft has ever visited Namaka, so we have no close-up pictures.
Namaka is the inner and smaller of the two known moons of the dwarf planet Haumea, as of August 2026. Haumea itself is a fast-rotating, elongated Kuiper Belt object about 1,740 km across at its equator, orbiting the Sun at an average distance of about 43 AU with a period of 285 years, and completing one rotation every 4 hours. Haumea is also the first Kuiper Belt object known to have a ring, confirmed in 2017.
Namaka was found by Michael E. Brown and the adaptive-optics team at the W. M. Keck Observatory in Hawaii, in Keck II images taken on 30 June 2005. The discovery was announced on 1 December 2005. Brown's team nicknamed it Blitzen; the larger moon, Hi'iaka, was Rudolph. The International Astronomical Union gave both moons their permanent names on 17 September 2008. Namaka is a water spirit and one of the daughters of Haumea, the Hawaiian goddess of fertility.
Namaka's diameter is poorly known. The commonly quoted estimate is about 150 km, with an uncertainty of roughly 50 km either way. Its mass is about 1.2 × 10^18 kg, roughly 0.05 per cent of Haumea's mass. Namaka orbits at a semi-major axis of about 25,700 km with a period of 18.28 days. The orbit is unusually eccentric, about 0.22 to 0.25, and steeply inclined, about 13 degrees, to Hi'iaka's orbit. These dynamics are thought to be shaped by Haumea's non-spherical mass distribution and by perturbations from Hi'iaka; the ratio of the two moons' periods, about 2.69, is close to an 8:3 resonance. The surface is mostly fresh water ice, yet Namaka is far fainter than either Haumea or Hi'iaka because it is so small. Both moons are believed to be fragments of an ancient collision that also produced the Haumea collisional family.
No spacecraft has visited Namaka, and none is currently scheduled. Everything known comes from ground-based telescopes, chiefly Keck II, and from the Hubble Space Telescope, which refined the moons' orbits. Between about 2008 and 2011 the moons' orbits were seen almost edge-on from Earth, and Namaka periodically passed in front of Haumea, giving astronomers rare eclipses to time.
Did you know?
- Namaka's discoverers first nicknamed it Blitzen, and Haumea's other moon Rudolph, because Haumea itself had been nicknamed Santa.
- Between 2008 and 2011, Namaka passed in front of Haumea as seen from Earth, letting astronomers time these rare eclipses.
- Nobody knows exactly how big Namaka is. The best guess is about 150 km across, but it might be only half that.
Neighbours around Haumea
Questions children ask
How big is Namaka?
Nobody is certain. Namaka is far too small and distant to see clearly, so astronomers estimate its size from its brightness. The best guess is about 150 kilometres across, but it could be 50 kilometres bigger or smaller than that.
Why is Namaka's orbit so strange?
Namaka's orbit is stretched and tilted rather than neat and circular. Haumea is egg-shaped and spins very quickly, so its gravity pulls unevenly, and the larger moon Hi'iaka tugs on Namaka too. Together these effects keep nudging Namaka's orbit about.
Has any spacecraft been to Namaka?
No. Namaka has never been visited, and no mission is planned. Everything we know comes from telescopes on Earth, especially the Keck II telescope in Hawaii, and from the Hubble Space Telescope, which helped measure the moons' orbits.
What does the name Namaka mean?
In Hawaiian tradition, Namaka is a water spirit and one of the daughters of Haumea, the goddess of fertility. Because the dwarf planet was named Haumea, its two moons were named after her daughters, Namaka and Hi'iaka, in 2008.
Quick quiz
Three questions for space cadets. Nothing is recorded.
- What is Namaka's surface mostly made of?
- About how long does Namaka take to orbit Haumea once?
- Which telescope was used to discover Namaka in 2005?
Hi'iaka
Haumea
MK2 (S/2015 (136472) 1)