Haumea (dwarf planet)

Haumea
2003EL61art.jpg
Artist's conception of Haumea with its moons Hiʻiaka and Namaka. The moons are actually much more distant than depicted here.
 
Discovery
Discovered by Brown et al.; Ortiz et al. (neither official)
Discovery date 2004 December 28 (Brown et al.); 2005 July (Ortiz et al.)
Designations
MPC designation (136108) Haumea
Alternate name 2003 EL61
Minor planet
category		 dwarf planet, plutoid, TNO (cubewano?)[1][2]
fifth-order 12:7 resonance?[3]
Epoch 2005-08-18 (JD 2 453 600.5)
Aphelion 7 708 Gm (51.526 AU)
Perihelion 5 260 Gm (35.164 AU)
Semi-major axis 6 484 Gm (43.335 AU)
Eccentricity 0.188 74
Orbital period 104 234 d (285.4 a)
Average orbital speed 4.484 km/s
Mean anomaly 198.07°
Inclination 28.19°
Longitude of ascending node 121.90°
Argument of perihelion 239.51°
Satellites 2
Physical characteristics
Dimensions ~1960 × 1518 × 996 km (Keck)[5]
(~1400 km)
1150 +250−100 km (Spitzer)[6]
Mass (4.2 ± 0.1)×1021 kg[7]
Mean density 2.6–3.3 g/cm³[5]
Equatorial surface gravity 0.44 m/s²
Escape velocity 0.84 km/s
Sidereal rotation
period		 0.163 146 ± 0.000 004 d
(3.915 5 ± 0.000 1 h)[8]
Albedo 0.7 ± 0.1[5]
Temperature <50 K[9]
Spectral type ?
Apparent magnitude 17.3 (opposition)[10]
Absolute magnitude (H) 0.17[4]

Haumea (pronounced /ˌhɑːuːˈmeɪə/ HAH-oo-MAY-ə), formal designation (136108) Haumea, is a dwarf planet in the Kuiper belt one-third the mass of Pluto.[note 1] It was discovered in 2004 by a team headed by Mike Brown of Caltech at the Palomar Observatory in the United States, and in 2005 by a team headed by J. L. Ortiz at the Sierra Nevada Observatory in Spain, though the latter claim has been contested. On September 17, 2008, it was accepted as a dwarf planet by the International Astronomical Union (IAU) and named after Haumea, the Hawaiian goddess of childbirth.

Haumea's extreme elongation makes it unique among known trans-Neptunian objects (TNOs). Although its shape has not been directly observed, calculations from its light curve suggest it is an ellipsoid, with its greatest axis twice as long as its shortest. Nonetheless, its gravity is believed sufficient for it to have relaxed into hydrostatic equilibrium, thereby meeting the definition of a dwarf planet. This elongation, along with its unusually rapid rotation, high density, and high albedo (due to a surface of crystalline water ice), are thought to be the results of a giant collision, which left Haumea the largest member of a collisional family that includes several large TNOs and its two known moons.

Contents

Classification

Haumea is a plutoid,[11] a term used to describe dwarf planets beyond Neptune's orbit. Its status as a dwarf planet means it is presumed to be massive enough to have been rounded by its own gravity, but not to have cleared its neighborhood of similar objects. Although Haumea appears to be far from spheroidal, its ellipsoidal shape is thought to result from its rapid rotation (in much the same way that a water balloon stretches out when tossed with a spin), and not from a lack of sufficient gravity to overcome the tensile strength of its material.[12] Haumea is provisionally listed as a classical Kuiper belt object (classical KBO) as it is not proven to be in orbital resonance with Neptune, nor is it likely to be significantly perturbed by the planet. Classical KBOs are the most numerous population of trans-Neptunian objects observed to date.[1] Should a resonance be proven, Haumea would qualify as a resonant rather than a classical KBO.

Name

Until it was given a permanent name, the Caltech discovery team used the nickname "Santa" among themselves, as they had discovered Haumea on December 28, 2004, just after Christmas.[13] The Spanish team proposed a separate discovery to the Minor Planet Center (MPC) in July 2005. On September 7, 2006, Haumea was given its first official label, the temporary designation (136108) 2003 EL61, with the "2003" based on the date of the Spanish discovery image.

Following guidelines established by the IAU that classical KBOs be given names of mythological beings associated with creation,[14] in September 2006 the Caltech team submitted formal names from Hawaiian mythology to the IAU for both (136108) 2003 EL61 and its moons, in order "to pay homage to the place where the satellites were discovered".[15] The names were proposed by David Rabinowitz of the Caltech team.[12] Haumea is the patron goddess of the island of Hawaiʻi, where the Mauna Kea Observatory is located. In addition, she is identified with Pāpā, the goddess of the earth and wife of Wākea (space),[16] which is appropriate because 2003 EL61 is thought to be composed almost entirely of solid rock, without the thick ice mantle over a small rocky core typical of other known Kuiper belt objects.[17][18] Lastly, Haumea is the goddess of fertility and childbirth, with many children who sprang from different parts of her body;[16] this corresponds to the swarm of icy bodies thought to have broken off the dwarf planet during an ancient collision.[18] The two known moons, also believed to have been born in this manner,[18] are thus named after two of Haumea's daughters, Hiʻiaka and Nāmaka.[17]

Discovery controversy

Main article: Controversy over the discovery of Haumea

Two teams claim credit for the discovery of Haumea. Mike Brown and his team at Caltech discovered Haumea in December 2004 on images they had taken on May 6, 2004. On July 20, 2005, they published an online abstract of a report intended to announce the discovery at a conference in September 2005.[19] At around this time, José Luis Ortiz Moreno and his team at the Instituto de Astrofísica de Andalucía at Sierra Nevada Observatory in Spain found Haumea on images taken on March 7–10, 2003.[20] Ortiz emailed the Minor Planet Center with their discovery on the night of July 27, 2005, giving a discovery date of March 7, 2003.[20]

Brown came to suspect the Spanish team of fraud upon learning that his observation logs were accessed from the Spanish observatory the day before the discovery announcement. These logs included enough information to allow the Ortiz team to precover Haumea in their 2003 images, and they were accessed again just before Ortiz scheduled telescope time to obtain confirmation images for a second announcement to the MPC on July 29. Ortiz later admitted he had accessed the Caltech observation logs but denied any wrongdoing, stating he was merely verifying whether they had discovered a new object.[21]

IAU protocol is that discovery credit for a minor planet goes to whoever first submits a report to the MPC with enough positional data for a decent determination of its orbit, and that the credited discoverer has priority in choosing a name. However, the IAU announcement on September 17, 2008, that Haumea had been accepted as a dwarf planet, made no mention of a discoverer. The location of discovery was listed as the Sierra Nevada Observatory of the Spanish team,[11][22] but the chosen name, Haumea, was the Caltech proposal.[20]

Orbit

Orbits of Haumea (yellow) and Pluto (red), relative to that of Neptune (grey), as of April 2006

Haumea has a typical orbit for a classical Kuiper belt object, with an orbital period of 285 Earth years, a perihelion of 35 AU, and an orbital inclination of 28°.[4] It passed aphelion in early 1992,[10] and is currently more than 50 AU from the Sun.

Haumea's orbit lies at a slightly higher inclination than the other members of its collisional family. This may be due to a possible 12:7 orbital resonance with Neptune. Such a resonance would have shifted its orbit over the course of the last billion years,[23] through the Kozai effect, which allows the exchange of an orbit's eccentricity for increased inclination.

With a visual magnitude of 17.5, Haumea is the third brightest object in the Kuiper belt after Pluto and Makemake, and easily observable with a large amateur telescope.[5] However, since the planets and most small Solar System bodies share a common orbital alignment from their formation in the primordial disk of the Solar System, most early surveys for distant objects focused on the projection on the sky of this common plane, called the ecliptic.[24] As the region of sky close to the ecliptic became well explored, later sky surveys began looking for objects that had been dynamically excited into orbits with higher inclinations, as well as more distant objects, with slower mean motions across the sky.[25][26] These surveys eventually covered the location of Haumea, with its high orbital inclination and current position far from the ecliptic.

Physical characteristics

The Earth Dysnomia (136199) Eris Charon (134340) Pluto (136472) Makemake (136108) Haumea (90377) Sedna (90482) Orcus (50000) Quaoar File:EightTNOs.png

Haumea compared to Eris, Pluto, Makemake, Sedna, Orcus, Quaoar, Varuna, and Earth (all to scale)

Since Haumea has moons, the mass of the system can be calculated from their orbits using Kepler's third law. The result is 4.2×1021 kg, 28% the mass of the Plutonian system and 6% the mass of the Earth's Moon. Nearly all of this mass is in Haumea.[7]

Haumea displays large fluctuations in brightness over a period of four hours, which can only be explained by a rotational period of this length. This is faster than any other known equilibrium body in the Solar System, and indeed faster than any other known body larger than 100 km in diameter.[5] This rapid rotation is thought to have been caused by the impact that created its satellites and collisional family.[18]

Size, shape, and composition

The size of a Solar System object can be derived from its optical magnitude, its distance, and its albedo. Objects appear bright to Earth observers either because they are large or or because they are highly reflective. If their reflectivity (albedo) can be ascertained, then a rough estimate can be made of their size. For most distant objects, the albedo is unknown, but Haumea is large and bright enough for its thermal emission to be measured, which has given an approximate value for its albedo and thus its size.[6] However, the calculation of its dimensions is complicated by its rapid rotation. The rotational physics of deformable bodies predicts that over as little as a hundred days,[5] a body rotating as rapidly as Haumea will have been distorted into the equilibrium form of a scalene ellipsoid. It is thought that most of the fluctuation in Haumea's brightness is caused not by local differences in albedo but by the alternation of the side view and end view as seen from Earth.[5]

The calculated ellipsoid shape of Haumea, 1960×1518×996 km. At left are the minimum and maximum equatorial silhouettes (1960×996 and 1518×996 km); at right is the view from the pole (1960×1518 km).

The rotation and amplitude of Haumea's light curve place strong constraints on its composition. If Haumea had a low density like Pluto, with a thick mantle of ice over a small rocky core, its rapid rotation would have elongated it to a greater extent than the fluctuations in its brightness allow. Such considerations constrain its density to a range of 2.6–3.3 g/cm³.[5][note 2] This range covers the values for silicate minerals such as olivine and pyroxene, which make up much of the rocky objects in the Solar System. This suggests that the bulk of Haumea is rock covered with a relatively thin layer of ice. A thick ice mantle more typical of Kuiper belt objects may have been blasted off during the impact that formed the Haumean collisional family.[18]

The denser the object in hydrostatic equilibrium, the more spherical it must be for a given rotational period, placing constraints on Haumea's possible dimensions. Fitting its mass, rotation, and inferred density to an equilibrium ellipsoid predicts that Haumea is approximately the diameter of Pluto along its longest axis and about half that at its poles.[5] This would make it one of the largest trans-Neptunian objects discovered, third or fourth after Eris, Pluto, and perhaps Makemake, and larger than Sedna, Orcus, or Quaoar.[27]

Surface

In addition to the large fluctuations in Haumea's light curve due to the body's shape, which affect all colors equally, smaller independent color variations found in 2008 show a region on the surface that differs both in color and albedo from the rest. Thus Haumea may have a mottled surface reminiscent of Pluto, if not as extreme.[8]

In 2005, the Gemini and Keck telescopes obtained spectra of Haumea which showed strong crystalline water ice features similar to the surface of Pluto's moon Charon.[9] This is peculiar, because crystalline ice forms at temperatures above 110 K, while the surface temperature of Haumea is below 50 K, a temperature at which amorphous ice is formed.[9] In addition, the structure of crystalline ice is unstable under the constant rain of cosmic rays and energetic particles from the Sun that strike trans-Neptunian objects.[9] The timescale for the crystalline ice to revert to amorphous ice under this bombardment is on the order of ten million years,[28] while trans-Neptunian objects have been in their present cold-temperature locations for timescales of thousands of millions of years.[23] Radiation damage should also redden and darken the surface of trans-Neptunian objects where the common surface materials of organic ices and tholin-like compounds are present, as is the case with Pluto. Therefore, the spectra and colour suggest Haumea and its family members have undergone recent resurfacing that produced fresh ice. However, no plausible resurfacing mechanism has been suggested.[29]

Haumea is as bright as snow, with an albedo in the range of 0.6–0.8, consistent with crystalline ice.[5] Other large TNOs such as Eris appear to have albedos as high or higher.[30] Best-fit modeling of the surface spectra suggests that 66% to 80% of the Haumean surface appears to be pure crystalline water ice, with one contributor to the high albedo possibly hydrogen cyanide or phyllosilicate clays.[9] Inorganic cyanide salts such as copper potassium cyanide may also be present.[9] In contrast to Makemake,[31] an absence of measurable methane in the spectra means that at most 10% of Haumea could be covered in methane ice, consistent with a warm collisional history that would have removed such volatiles.[9]

Moons

Main articles: Moons of Haumea, Hi'iaka (moon), and Namaka (moon)

Two small satellites have been discovered orbiting Haumea, (136108) Haumea I Hiʻiaka and (136108) Haumea II Namaka.[11] Brown's team discovered both in 2005, through observations of Haumea using the W.M. Keck Observatory.

Hiʻiaka, at first nicknamed "Rudolph" by the Caltech team,[32] was discovered January 26, 2005.[33] It is the outer and, at roughly 310 km in diameter, the larger and brighter of the two, and orbits Haumea in a nearly circular path every 49 days.[34] Strong absorption features at 1.5 and 2 micrometres in the infrared spectrum are consistent with nearly pure crystalline water ice covering much of the surface.[35] The unusual spectrum, along with similar absorption lines on Haumea, led Brown and colleagues to conclude that capture was an unlikely model for the system's formation, and that the Haumean moons must be fragments of Haumea itself.[23]

Namaka, the smaller, inner satellite of Haumea, was discovered on June 30, 2005, and nicknamed "Blitzen". It is a tenth the mass of Hiʻiaka, orbits Haumea in 18 days in a highly elliptical, non-Keplerian orbit, and as of 2008 is inclined 13° from the larger moon, which perturbs its orbit.[36]

At present, the orbits of the Haumean moons appear almost exactly edge-on from Earth, with the moons potentially occulting Haumea.[37] Observation of such transits would provide precise information on the size and shape of Haumea and its moons, as happened in the late 1980s with Pluto and Charon.[38] The tiny change in brightness of the system during these occultations will require at least a medium-aperture professional telescope for detection.[39] Hiʻiaka last occulted Haumea in 1999, a few years before discovery, and will not do so again for some 130 years.[40] However, in a situation unique among regular satellites, Namaka's orbit is being greatly torqued by Hiʻiaka, preserving the viewing angle of Namaka–Haumea transits for several more years.[36][39]

Collisional family

Main article: Haumea family

Haumea is the largest member of its collisional family, a group of astronomical objects with similar physical and orbital characteristics thought to have formed when a larger progenitor was shattered by an impact.[18] This family is the first to be identified among TNOs and includes—beside Haumea and its moons—(55636) 2002 TX300 (~600 km), (24835) 1995 SM55 (< 700 km), (19308) 1996 TO66 (~500 km), (120178) 2003 OP32 (< 700 km), and (145453) 2005 RR43 (< 700 km).[3]

The presence of the collisional family could imply that Haumea and its "offspring" might have originated in the scattered disc. In today's sparsely populated Kuiper belt, the chance of such a collision occurring over the age of the Solar System is less than 0.1 percent.[41] The family could not have formed in the denser primordial Kuiper belt because such a close-knit group would have been disrupted by Neptune's migration into the belt—the believed cause of the belt's current low density.[41] Therefore it appears likely that the dynamic scattered disc region, in which the possibility of such a collision is far higher, is the place of origin for the object that generated Haumea and its kin.[41]

Because it would have taken at least a billion years for the group to have diffused as far as it has, the collision which created the Haumea family is believed to have occurred very early in the Solar System's history.[3]

Notes

  1. ↑ Haumea is 1400 times less massive than Earth (0.07% the mass of Earth).
  2. ↑ By comparison, Earth's rocky moon has a density of 3.3 g/cm³, while Pluto, which is typical of icy objects in the Kuiper belt, has a density of 2.0 g/cm³.

References

  1. ↑ 1.0 1.1 "Minor Planet Electronic Circular 2008-O05 : Distant Minor Planets (2008 AUG. 2.0 TT)" ((older provisional Cubewano listing)). Minor Planet Center (2008-07-17). Retrieved on 2008-09-27.
  2. ↑ Marc W. Buie (2008-06-25). "Orbit Fit and Astrometric record for 136108". Southwest Research Institute (Space Science Department). Retrieved on 2008-10-02.
  3. ↑ 3.0 3.1 3.2 D. Ragozzine; M. E. Brown (2007-09-04). "Candidate Members and Age Estimate of the Family of Kuiper Belt Object 2003 EL61". The Astronomical Journal 134 (6): 2160–2167. doi:10.1086/522334. http://adsabs.harvard.edu/abs/2007arXiv0709.0328R. Retrieved on 2008-09-19. 
  4. ↑ 4.0 4.1 4.2 "Jet Propulsion Laboratory Small-Body Database Browser: 136108 Haumea ((2003 EL61)". NASA's Jet Propulsion Laboratory (2008-05-10 last obs). Retrieved on 2008-06-11.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 D. L. Rabinowitz, K. M. Barkume, M. E. Brown, H. G. Roe, M. Schwartz, S. W. Tourtellotte, C. A. Trujillo (2006). "Photometric Observations Constraining the Size, Shape, and Albedo of 2003 EL61, a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt" (preprint on arXiv). The Astrophysical Journal 639 (2): 1238–1251. doi:10.1086/499575. 
  6. ↑ 6.0 6.1 John Stansberry, Will Grundy, Mike Brown, Dale Cruikshank, John Spencer, David Trilling, Jean-Luc Margot (2007-02-20). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". University of Arizona, Lowell Observatory, California Institute of Technology, NASA Ames Research Center, Southwest Research Institute, Cornell University. Retrieved on 2008-07-27.
  7. ↑ 7.0 7.1 M. E. Brown, A. H. Bouchez, D. L. Rabinowitz, R. Sari, C. A. Trujillo, M. A. van Dam, R. Campbell, J. Chin, S. Hartman, E. Johansson, R. Lafon, D. LeMignant, P. Stomski, D. Summers, P. L. Wizinowich (October 2005). "Keck Observatory laser guide star adaptive optics discovery and characterization of a satellite to large Kuiper belt object 2003 EL61" (full text from Caltech). The Astrophysical Journal Letters 632: L45. doi:10.1086/497641. 
  8. ↑ 8.0 8.1 Pedro Lacerda, David Jewitt and Nuno Peixinho (2008-04-02). "High-Precision Photometry of Extreme KBO 2003 EL61". The Astronomical Journal 135: 1749–1756. doi:10.1088/0004-6256/135/5/1749. http://www.iop.org/EJ/abstract/1538-3881/135/5/1749. Retrieved on 2008-09-22. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 Chadwick A. Trujillo, Michael E. Brown, Kristina Barkume, Emily Shaller, David L. Rabinowitz (February 2007). "The Surface of 2003 EL61 in the Near Infrared" (preprint). The Astrophysical Journal 655: 1172–1178. doi:10.1086/509861. 
  10. ↑ 10.0 10.1 "HORIZONS Web-Interface". NASA Jet Propulsion Laboratory Solar System Dynamics. Retrieved on 2008-07-02.
  11. ↑ 11.0 11.1 11.2 "Dwarf Planets and their Systems", US Geological Survey Gazetteer of Planetary Nomenclature. Retrieved on 2008-09-17. 
  12. ↑ 12.0 12.1 "IAU names fifth dwarf planet Haumea", IAU Press Release (2008-09-17). Retrieved on 2008-09-17. 
  13. ↑ "Santa et al.". NASA Astrobiology Magazine (2005-09-10). Retrieved on 2008-10-16.
  14. ↑ "Naming of astronomical objects: Minor planets", International Astronomical Union. Retrieved on 2008-11-17. 
  15. ↑ Mike Brown (2008-09-17). "Dwarf planets: Haumea". CalTech. Retrieved on 2008-09-18.
  16. ↑ 16.0 16.1 Robert D. Craig (2004). Handbook of Polynesian Mythology. ABC-CLIO. pp. 128. http://books.google.ca/books?id=LOZuirJWXvUC&pg=PA128&dq=haumea&lr=&sig=ACfU3U3pDIRAYQihFLO5R-rkQ1Y2G3OHxg. 
  17. ↑ 17.0 17.1 "News Release - IAU0807: IAU names fifth dwarf planet Haumea". International Astronomical Union (2008-09-17). Retrieved on 2008-09-18.
  18. ↑ 18.0 18.1 18.2 18.3 18.4 18.5 Michael E. Brown, Kristina M. Barkume; Darin Ragozzine; Emily L. Schaller (2007-01-19). "A collisional family of icy objects in the Kuiper belt". Nature 446 (7133): 294–296. doi:10.1038/nature05619. 
  19. ↑ Michael E Brown. "The electronic trail of the discovery of 2003 EL61". CalTech. Retrieved on 2006-08-16.
  20. ↑ 20.0 20.1 20.2 Pablo Santos Sanz (2008-09-26). "La historia de Ataecina vs Haumea" (in Spanish). infoastro.com. Retrieved on 2008-09-29.
  21. ↑ Jeff Hecht (2005-09-21). "Astronomer denies improper use of web data", NewScientist.com. Retrieved on 2006-08-16. 
  22. ↑ Rachel Courtland (2008-09-19). "Controversial dwarf planet finally named 'Haumea'". NewScientistSpace. Retrieved on 2008-09-19.
  23. ↑ 23.0 23.1 23.2 Michael E. Brown. "The largest Kuiper belt objects" (PDF). CalTech. Retrieved on 2008-09-19.
  24. ↑ C. A. Trujillo and M. E. Brown (June 2003). The Caltech Wide Area Sky Survey. Earth Moon and Planets. 112. pp. 92–99. doi:10.1023/B:MOON.0000031929.19729.a1. (inactive 2008-10-12). 
  25. ↑ M. E. Brown, C. Trujillo, D. L. Rabinowitz (2004). "Discovery of a candidate inner Oort cloud planetoid". The Astrophysical Journal 617 (1): 645–649. doi:10.1086/422095. 
  26. ↑ M. E. Schwamb, M. E. Brown, D. L. Rabinowitz (2008). "Constraints on the distant population in the region of Sedna". American Astronomical Society (DPS meeting \#40}, \#38.07). 
  27. ↑ J. Stansberry, W. Grundy, M. Brown, et al. (2008-04-17). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope" (abstract). The Solar System beyond Neptune (University of Arizona Press). http://arxiv.org/abs/astro-ph/0702538v1. Retrieved on 2008-08-04. 
  28. ↑ "Charon: An ice machine in the ultimate deep freeze". Gemini Observatory (2007-07-17). Retrieved on 2007-07-18.
  29. ↑ David L. Rabinowitz, Bradley E. Schaefer, Martha W. Schaefer, Suzanne W. Tourtellotte (2008-04-17). "The Youthful Appearance of the 2003 EL61 Collisional Family". ArXiv.org. http://arxiv.org/abs/0804.2864. Retrieved on 2008-09-20. 
  30. ↑ M. E. Brown, E.L. Schaller, H.G. Roe, D. L. Rabinowitz, C. A. Trujillo (2006-02-08). "Direct measurement of the size of 2003 UB313 from the Hubble Space Telescope" (PDF). The Astronomical Journal 643 (2): L61–L63. doi:10.1086/504843. http://www.gps.caltech.edu/~mbrown/papers/ps/xsize.pdf. 
  31. ↑ S.C. Tegler, W. Grundy, W. Romanishin, G. Consolmagno, K. Mogren, F. Vilas. "Optical Spectroscopy of the Large Kuiper Belt Objects 136472 (2005 FY9) and 136108 (2003 EL61)". Retrieved on 2008-10-19.
  32. ↑ Kenneth Chang (2007-03-20). "Piecing Together the Clues of an Old Collision, Iceball by Iceball". New York Times. Retrieved on 2008-10-12.
  33. ↑ M. E. Brown, A. H. Bouchez, D. Rabinowitz. R. Sari, C. A. Trujillo, M. van Dam, R. Campbell, J. Chin, S. Hardman, E. Johansson, R. Lafon, D. Le Mignant, P. Stomski, D. Summers, and P. Wizinowich (2005-09-02). "Keck Observatory Laser Guide Star Adaptive Optics Discovery and Characterization of a Satellite to the Large Kuiper Belt Object 2003 EL61". The Astrophysical Journal Letters 632: L45–L48. doi:10.1086/497641. http://www.journals.uchicago.edu/doi/pdf/10.1086/497641. 
  34. ↑ M. E. Brown, M. A. van Dam, A. H. Bouchez et. al. (2005-10-02). "Satellites of the largest Kuiper belt objects" (PDF). The Astrophysical Journal 639: 43–46. doi:10.1086/501524. http://web.gps.caltech.edu/~mbrown/papers/ps/gab.pdf. Retrieved on 2009-09-29. 
  35. ↑ K. M Barkume, M. E. Brown, and E. L. Schaller (March 2006). "preprint Water Ice on the Satellite of Kuiper Belt Object 2003 EL61". The Astrophysical Journal 640: L87–L89. doi:10.1086/503159. http://arxiv.org/abs/astro-ph/0601534 preprint. 
  36. ↑ 36.0 36.1 D. Ragozzine, M. E. Brown, C. A. Trujillo, E. L. Schaller. "Orbits and Masses of the 2003 EL61 Satellite System". AAS DPS conference 2008. Retrieved on 2008-10-17.
  37. ↑ "IAU Circular 8949". International Astronomical Union (2008-09-17). Retrieved on 2008-12-06.
  38. ↑ Lucy-Ann Adams McFadden, Paul Robert Weissman, Torrence V. Johnson. "Encyclopedia of the Solar System". Retrieved on 2008-10-17.
  39. ↑ 39.0 39.1 D. C. Fabrycky, M. J. Holman, D. Ragozzine, M. E. Brown, T. A. Lister, D. M. Terndrup, J. Djordjevic, E. F. Young, L. A. Young, R. R. Howell. "Mutual Events of 2003 EL61 and its Inner Satellite". AAS DPS conference 2008. Retrieved on 2008-10-17.
  40. ↑ Mike Brown (2008-05-18). "Moon shadow Monday (fixed)". Mike Brown's Planets. Retrieved on 2008-09-27.
  41. ↑ 41.0 41.1 41.2 Harold F. Levison, Alessandro Morbidelli, David Vokrouhlický and William F. Bottke (2008-04-14). "On a Scattered Disc Origin for the 2003 EL61 Collisional Family—an Example of the Importance of Collisions in the Dynamics of Small Bodies". The Astronomical Journal 136: 1079–1088. doi:10.1088/0004-6256/136/3/1079. http://www.iop.org/EJ/abstract/1538-3881/136/3/1079. Retrieved on 2008-09-19. 

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Haumea
Moons
Namaka · Hiʻiaka
 Artistic impression of Haumea and its two known satellites
Classification
Dwarf planet · Plutoid · Definition of planet · 2006 definition of planet · Kuiper belt · Cubewano  · Trans-Neptunian object
Collisional family
2002 TX300  · (24835) 1995 SM55  · (19308) 1996 TO66  · (120178) 2003 OP32  · (145453) 2005 RR43
Controversy
Controversy over the discovery of Haumea  · José Luis Ortiz Moreno  · Michael E. Brown
Minor planets navigator

(136107) 2003 EY58       ·       (136108) Haumea       ·       (136109) 2003 FA22
Plutoids (trans-Neptunian dwarf planets) and Plutoid candidates
Kuiper belt
Orcus · 2003 AZ84 · Ixion · Pluto · 2005 RN43 · 2002 MS4 · 2002 UX25 · Varuna · Haumea  · 2002 TX300 · 2005 UQ513 · Quaoar · Makemake · 2003 MW12 · 2002 AW197
Scattered disc
2002 TC302 · 2006 QH181 · Eris · 2007 UK126 · 2005 QU182 · Sedna
See also Triton · List of trans-Neptunian objects · List of objects in the Solar System (by radius · by mass)
For a pronunciation guide, see Centaur and TNO pronunciation. Plutoids are bolded, candidates are not.