# Makemake

Makemake (minor-planet designation 136472 Makemake) is a likely dwarf planet and perhaps the second largest Kuiper belt object[f] in the classical population,[a] with a diameter approximately two-thirds that of Pluto.[19][20] Makemake has one known satellite, S/2015 (136472) 1.[21] Makemake's extremely low average temperature, about 40 K (−230 °C), means its surface is covered with methane, ethane, and possibly nitrogen ices.[16]

Discovery Makemake and its moon (indicated by the arrow), as seen by the Hubble Space Telescope March 31, 2005 (136472) Makemake /ˌmækiˈmæki/, /ˌmɑːkiˈmɑːki/ or [b] Makemake 2005 FY9 Dwarf planetcubewano[1]scattered-near[a] Makemakean Epoch JD 2458600.5 (27 April 2019) January 29, 1955 52.761 AU 7.8929×109 km 38.360 AU 5.7386×109 km 45.561 AU 6.8158×109 km 0.15804 307.53 yr (112,327 d) 4.419 km/s 163.9435° 28.98030° 79.6459° 295.0896° 1 (1434+48−18) × projected (1420+18−24 km)[7] (1502±45) × (1430±9) km[8] 715+19−11 km[7] 739±17 km[8] 0.0098[c] 0.048[d] (6.9±0.3)×106 km2[e][9] (1.7±0.1)×109 km3[e][10] < 4.4 × 1021 kg< (0.000736726 Earths) 1.4–3.2 g/cm3[7] <3.05 g/cm3 < 0.57 < 0.91 22.8266±0.0001 h[11] 0.81+0.03−0.05[7] 32–36 K (single-terrain model) 40–44 K (two-terrain model)[8] B−V=0.83, V−R=0.5[12] 17.0 (opposition)[13][14] −0.3[6]0.049±0.02[11]

Makemake was discovered on March 31, 2005, by a team led by Michael E. Brown, and announced on July 29, 2005. Initially, it was known as 2005 FY9 and later given the minor-planet number 136472. In July 2008 it was named after Makemake, the creator god of the Rapa Nui people of Easter Island, under the expectation by the International Astronomical Union (IAU) that it would prove to be a dwarf planet.[20][22][23][24]

## History

### Discovery

Makemake was discovered on March 31, 2005, by a team at the Palomar Observatory, led by Michael E. Brown,[6] and was announced to the public on July 29, 2005. The team had planned to delay announcing their discoveries of the bright objects Makemake and Eris until further observations and calculations were complete, but announced them both on July 29 when the discovery of another large object they had been tracking, Haumea, was controversially announced on July 27 by a different team in Spain.[25]

Despite its relative brightness (it is about a fifth as bright as Pluto),[g] Makemake was not discovered until after many much fainter Kuiper belt objects. Most searches for minor planets are conducted relatively close to the ecliptic (the region of the sky that the Sun, Moon and planets appear to lie in, as seen from Earth), due to the greater likelihood of finding objects there. It probably escaped detection during the earlier surveys due to its relatively high orbital inclination, and the fact that it was at its farthest distance from the ecliptic at the time of its discovery, in the northern constellation of Coma Berenices.[14]

Precovery images have been identified back to January 29, 1955.[6]

Besides Pluto, Makemake is the only other dwarf planet that was bright enough that Clyde Tombaugh could have detected it during his search for trans-Neptunian planets around 1930.[27] At the time of Tombaugh's survey, Makemake was only a few degrees from the ecliptic, near the border of Taurus and Auriga,[h] at an apparent magnitude of 16.0.[14] This position, however, was also very near the Milky Way, and Makemake would have been almost impossible to find against the dense background of stars. Tombaugh continued searching for some years after the discovery of Pluto,[28] but he did not find Makemake or any other trans-Neptunian objects.

### Name

The provisional designation 2005 FY9 was given to Makemake when the discovery was made public. Before that, the discovery team used the codename "Easterbunny" for the object, because of its discovery shortly after Easter.[2]

In July 2008, in accordance with IAU rules for classical Kuiper belt objects, 2005 FY9 was given the name of a creator deity.[29] The name of Makemake, the creator of humanity and god of fertility in the myths of the Rapa Nui, the native people of Easter Island,[23] was chosen in part to preserve the object's connection with Easter.[2]

## Orbit and classification

Orbits of Makemake (blue), Haumea (green), contrasted with the orbit of Pluto (red) and the ecliptic (grey). The perihelia (q)[6] and the aphelia (Q) are marked with the dates of passage. The positions on April 2006 are marked with the spheres illustrating relative sizes and differences in albedo and colour.

Makemake's orbit outside of Neptune is similar to Haumea's. The positions are as of 1 January 2018.

As of April 2019, Makemake is 52.5 AU (7.85×109 km) from the Sun,[13][14] almost as far from the Sun as it ever reaches on its orbit.[16] Makemake follows an orbit very similar to that of Haumea: highly inclined at 29° and a moderate eccentricity of about 0.16.[30] Nevertheless, Makemake's orbit is slightly farther from the Sun in terms of both the semi-major axis and perihelion. Its orbital period is 308 years,[6] more than Pluto's 248 years and Haumea's 285 years. Both Makemake and Haumea are currently far from the ecliptic—the angular distance is almost 29°. Makemake is approaching its 2033 aphelion,[14] whereas Haumea passed its aphelion in early 1992.[31]

Makemake is a classical Kuiper belt object (KBO),[1][a] which means its orbit lies far enough from Neptune to remain stable over the age of the Solar System.[32][33] Unlike plutinos, which can cross Neptune's orbit due to their 2:3 resonance with the planet, the classical objects have perihelia further from the Sun, free from Neptune's perturbation.[32] Such objects have relatively low eccentricities (e below 0.2) and orbit the Sun in much the same way the planets do. Makemake, however, is a member of the "dynamically hot" class of classical KBOs, meaning that it has a high inclination compared to others in its population.[34] Makemake is, probably coincidentally, near the 11:6 resonance with Neptune.[35]

## Physical characteristics

### Brightness, size, and rotation

Makemake (apparent magnitude 16.9) with edge on galaxy IC 3587

Makemake is currently visually the second-brightest Kuiper belt object after Pluto,[27] having a March opposition apparent magnitude of 17.0[13] it will pass from its present constellation Coma Berenices to Boötes in December 2027.[14] It is bright enough to be visible using a high-end amateur telescope.

Combining the detection in infrared by the Spitzer Space Telescope and Herschel Space Telescope with the similarities of spectrum with Pluto yielded an estimated diameter from 1,360 to 1,480 km.[19] From the 2011 stellar occultation by Makemake, its dimensions have been initially measured to be (1502 ± 45) × (1430 ± 9) km. However, the occultation data was later reanalyzed,[7] which led to the dimension estimate of (1434+48
−18
) × (1420+18
−24
km)
without a pole-orientation constraint.[7] Makemake was the fourth dwarf planet recognized, because it has a bright V-band absolute magnitude of −0.44.[6] Makemake has a high geometrical albedo of 0.81+0.01
−0.02
.[7]

The rotation period of Makemake is estimated at 22.83 hours.[11] A rotation period of 7.77 hours published in 2009[36] later turned out to be an alias of the actual rotation period. The possibility of this had been mentioned in the 2009 study, and the data from that study agrees well with the 22.83 hour period.[11] This rotation period is relatively long for a dwarf planet. Part of this may be due to tidal acceleration from Makemake's satellite. It has been suggested that a second large, undiscovered satellite might better explain the dwarf planet's unusually long rotation.[11]

Makemake's lightcurve amplitude is small, only 0.03 mag.[7][11] This was thought to be due to Makemake currently being viewed pole on from Earth; however, S/2015 (136472) 1's orbital plane (which is probably orbiting with little inclination relative to Makemake's equator due to tides resulting from its rapid rotation) is edge-on from Earth, implying that Makemake is really being viewed equator-on.[37]

Artistic comparison of Pluto, Eris, Haumea, Makemake, 2007 OR10, Quaoar, Sedna, 2002 MS4, Orcus, Salacia, and Earth along with the Moon.

### Spectra and surface

Like Pluto, Makemake appears red in the visible spectrum, and significantly redder than the surface of Eris (see colour comparison of TNOs).[38] The near-infrared spectrum is marked by the presence of the broad methane (CH4) absorption bands. Methane is observed also on Pluto and Eris, but its spectral signature is much weaker.[38]

Spectral analysis of Makemake's surface revealed that methane must be present in the form of large grains at least one centimetre in size.[16] In addition to methane, large amounts of ethane and tholins as well as smaller amounts of ethylene, acetylene and high-mass alkanes (like propane) may be present, most likely created by photolysis of methane by solar radiation.[16][39] The tholins are probably responsible for the red color of the visible spectrum. Although evidence exists for the presence of nitrogen ice on its surface, at least mixed with other ices, there is nowhere near the same level of nitrogen as on Pluto and Triton, where it composes more than 98 percent of the crust. The relative lack of nitrogen ice suggests that its supply of nitrogen has somehow been depleted over the age of the Solar System.[16][40][41]

The far-infrared (24–70 μm) and submillimeter (70–500 μm) photometry performed by Spitzer and Herschel telescopes revealed that the surface of Makemake is not homogeneous. Although the majority of it is covered by nitrogen and methane ices, where the albedo ranges from 78 to 90%, there are small patches of dark terrain whose albedo is only 2 to 12%, and that make up 3 to 7% of the surface.[19] These studies were made before S/2015 (136472) 1 was discovered; thus, these small dark patches may actually have been the dark surface of the satellite rather than any actual surface features on Makemake.[37] However, some experiments have refuted these studies. Spectroscopic studies, collected from 2005 to 2008 using the William Herschel Telescope (La Palma, Spain) were analyzed together with other spectra in the literature, as of 2014. They show some degree of variation in the spectral slope, which would be associated with different abundance of the complex organic materials, byproduct of the irradiation of the ices present on the surface of Makemake. However, the relative ratio of the two dominant icy species, methane and nitrogen, remains quite stable on the surface revealing a low degree of inhomogeneity in the ice component.[42] These results have been recently confirmed when the Telescopio Nazionale Galileo acquired new visible and near infra-red spectra for Makemake, between 2006 and 2013, that covered nearly 80% of its surface; this study found that the variation in the spectra were negligible, suggesting that Makemake's surface may indeed be homogenous.[43] Based on optical observations conducted between 2006 and 2017, Hromakina et al. concluded that Makemake's lightcurve was likely due to heterogeneities across its surface, but that the variations (of the order of 3%) were too small to have been detected spectroscopically.[11]

### Atmosphere

Makemake was expected to have an atmosphere similar to that of Pluto but with a lower surface pressure. However, on 23 April 2011 Makemake passed in front of an 18th-magnitude star and abruptly blocked its light.[44] The results showed that Makemake presently lacks a substantial atmosphere and placed an upper limit of 4–12 nanobar on the pressure at its surface.[8]

The presence of methane and possibly nitrogen suggests that Makemake could have a transient atmosphere similar to that of Pluto near its perihelion.[38] Nitrogen, if present, will be the dominant component of it.[16] The existence of an atmosphere also provides a natural explanation for the nitrogen depletion: because the gravity of Makemake is weaker than that of Pluto, Eris and Triton, a large amount of nitrogen was probably lost via atmospheric escape; methane is lighter than nitrogen, but has significantly lower vapor pressure at temperatures prevalent at the surface of Makemake (32–36 K),[8] which hinders its escape; the result of this process is a higher relative abundance of methane.[45] However, studies of Pluto's atmosphere by New Horizons suggest that methane, not nitrogen, is the dominant escaping gas, suggesting that the reasons for Makemake's absence of nitrogen may be more complicated.[46][47]

## Satellite

Makemake has a single known moon, which was discovered in 2015 or 2016. It is probably less than 200 km in diameter.[48]

## Exploration

It has been calculated that a flyby mission to Makemake could take just over 16 years using a Jupiter gravity assist, based on a launch date of 21 August 2024 or 24 August 2036. Makemake would be approximately 52 AU from the Sun when the spacecraft arrives.[49]

## Notes

1. ^ a b c Astronomers Mike Brown, David Jewitt and Marc Buie classify Makemake as a near scattered object but the Minor Planet Center, from which Wikipedia draws most of its definitions for the trans-Neptunian population, places it among the main Kuiper belt population.[15][16][17][18]
2. ^ The Rapa Nui pronunciation is [ˈmakeˈmake], which is approximated in English as MAH-kee-MAH-kee,[2] MAK-ee-MAK-ee, or as /ˌmɑːkˈmɑːk/ MAH-kay-MAH-kay.[3][4] The first two are anglicized pronunciations; the last is closer to the Polynesian, and is used by Brown and his students.[5]
3. ^ Calculated using (a−b)/a and the dimensions from Brown[7]
4. ^ Calculated using (a−b)/a and the dimensions from Ortiz et al.[8]
5. ^ a b Calculated using the dimensions from [8] assuming an oblate spheroid.
6. ^ The Kuiper Belt is a ring of bodies beyond Neptune.
7. ^ It has an apparent magnitude in opposition of 16.7 vs. 15 for Pluto.[26]
8. ^ Based on Minor Planet Center online Minor Planet Ephemeris Service: March 1, 1930: RA: 05h51m, Dec: +29.0.

## References

1. ^ a b "MPEC 2009-P26 :Distant Minor Planets (2009 AUG. 17.0 TT)". IAU Minor Planet Center. 2009-08-07. Retrieved 2009-08-28.
2. ^ a b c Brown, Mike (2008). "Mike Brown's Planets: What's in a name? (part 2)". California Institute of Technology. Retrieved 2008-07-14.
3. ^ Brown, Mike (2008). "Mike Brown's Planets: Make-make". California Institute of Technology. Retrieved 2008-07-14.
4. ^ Robert D. Craig (2004). Handbook of Polynesian Mythology. ABC-CLIO. p. 63. ISBN 978-1-57607-894-5.
5. ^ Podcast Dwarf Planet Haumea (Darin Ragozzine, at 3′11″)
6. "JPL Small-Body Database Browser: 136472 Makemake (2005 FY 9)". NASA Jet Propulsion Laboratory (2018-05-23 last obs). Retrieved 2019-04-09.
7. M.E. Brown (2013). "On the size, shape, and density of dwarf planet Makemake". The Astrophysical Journal Letters. 767 (1): L7(5pp). arXiv:1304.1041v1. Bibcode:2013ApJ...767L...7B. doi:10.1088/2041-8205/767/1/L7.
8. Ortiz, J. L.; Sicardy, B.; Braga-Ribas, F.; Alvarez-Candal, A.; Lellouch, E.; Duffard, R.; Pinilla-Alonso, N.; Ivanov, V. D.; Littlefair, S. P.; Camargo, J. I. B.; Assafin, M.; Unda-Sanzana, E.; Jehin, E.; Morales, N.; Tancredi, G.; Gil-Hutton, R.; De La Cueva, I.; Colque, J. P.; Da Silva Neto, D. N.; Manfroid, J.; Thirouin, A.; Gutiérrez, P. J.; Lecacheux, J.; Gillon, M.; Maury, A.; Colas, F.; Licandro, J.; Mueller, T.; Jacques, C.; Weaver, D. (2012). "Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation". Nature. 491 (7425): 566–569. Bibcode:2012Natur.491..566O. doi:10.1038/nature11597. PMID 23172214. (ESO 21 November 2012 press release: Dwarf Planet Makemake Lacks Atmosphere)
9. ^
10. ^
11. T. A. Hromakina; I. N. Belskaya; Yu. N. Krugly; V. G. Shevchenko; J. L. Ortiz; P. Santos-Sanz; R. Duffard; N. Morales; A. Thirouin; R. Ya. Inasaridze; V. R. Ayvazian; V. T. Zhuzhunadze; D. Perna; V. V. Rumyantsev; I. V. Reva; A. V. Serebryanskiy; A. V. Sergeyev; I. E. Molotov; V. A. Voropaev; S. F. Velichko (2019-04-09). "Long-term photometric monitoring of the dwarf planet (136472) Makemake". Astronomy & Astrophysics. 625: A46. arXiv:1904.03679. Bibcode:2019A&A...625A..46H. doi:10.1051/0004-6361/201935274.
12. ^ Snodgrass, C.; Carry, B.; Dumas, C.; Hainaut, O. (February 2010). "Characterisation of candidate members of (136108) Haumea's family". Astronomy and Astrophysics. 511: A72. arXiv:0912.3171. Bibcode:2010A&A...511A..72S. doi:10.1051/0004-6361/200913031.
13. ^ a b c "AstDys (136472) Makemake Ephemerides". Department of Mathematics, University of Pisa, Italy. Retrieved 2019-04-09.
14. "Asteroid 136472 Makemake (2005 FY9)". HORIZONS Web-Interface. JPL Solar System Dynamics. Retrieved 2015-12-30.
15. ^ Marc W. Buie (2008-04-05). "Orbit Fit and Astrometric record for 136472". SwRI (Space Science Department). Retrieved 2008-07-13.
16. Mike Brown; K. M. Barksume; G. L. Blake; E. L. Schaller; et al. (2007). "Methane and Ethane on the Bright Kuiper Belt Object 2005 FY9" (PDF). The Astronomical Journal. 133 (1): 284–289. Bibcode:2007AJ....133..284B. doi:10.1086/509734.
17. ^ Audrey Delsanti; David Jewitt. "The Solar System Beyond The Planets" (PDF). University of Hawaii. Retrieved 2008-08-03.
18. ^ "List Of Transneptunian Objects". Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 2008-08-03.
19. ^ a b c T.L. Lim; J. Stansberry; T.G. Müller (2010). ""TNOs are Cool": A survey of the trans-Neptunian region III. Thermophysical properties of 90482 Orcus and 136472 Makemake". Astronomy and Astrophysics. 518: L148. arXiv:1202.3657. Bibcode:2010A&A...518L.148L. doi:10.1051/0004-6361/201014701.
20. ^ a b International Astronomical Union (2008-07-19). "Fourth dwarf planet named Makemake" (Press release). International Astronomical Union (News Release – IAU0806). Retrieved 2008-07-20.
21. ^ HubbleSite (2016-04-26). "Hubble Discovers Moon Orbiting the Dwarf Planet Makemake" (Press release). HubbleSite (News Release no. STScI-2016-18). Retrieved 2016-04-26.
22. ^ Michael E. Brown. "The Dwarf Planets". California Institute of Technology, Department of Geological Sciences. Retrieved 2008-01-26.
23. ^ a b "Dwarf Planets and their Systems". Working Group for Planetary System Nomenclature (WGPSN). U.S. Geological Survey. 2008-11-07. Retrieved 2008-07-13.
24. ^ Gonzalo Tancredi; Sofia Favre (June 2008). "Which are the dwarfs in the Solar System?" (PDF). Icarus. 195 (2): 851–862. Bibcode:2008Icar..195..851T. doi:10.1016/j.icarus.2007.12.020. Retrieved 2008-08-03.
25. ^ Thomas H. Maugh II & John Johnson Jr. (2005-10-16). "His Stellar Discovery Is Eclipsed". Los Angeles Times. Retrieved 2008-07-14.
26. ^ David L. Rabinowitz; Bradley E. Schaefer; Suzanne W. Tourtellotte (2007). "The Diverse Solar Phase Curves of Distant Icy Bodies. I. Photometric Observations of 18 Trans-Neptunian Objects, 7 Centaurs, and Nereid". The Astronomical Journal. 133 (1): 26–43. arXiv:astro-ph/0605745. Bibcode:2007AJ....133...26R. doi:10.1086/508931.
27. ^ a b Brown, M. E.; Van Dam, M. A.; Bouchez, A. H.; Le Mignant, D.; Campbell, R. D.; Chin, J. C. Y.; Conrad, A.; Hartman, S. K.; Johansson, E. M.; Lafon, R. E.; Rabinowitz, D. L. Rabinowitz; Stomski, P. J., Jr.; Summers, D. M.; Trujillo, C. A.; Wizinowich, P. L. (2006). "Satellites of the Largest Kuiper Belt Objects" (PDF). The Astrophysical Journal. 639 (1): L43–L46. arXiv:astro-ph/0510029. Bibcode:2006ApJ...639L..43B. doi:10.1086/501524. Retrieved 2011-10-19.
28. ^ "Clyde W. Tombaugh". New Mexico Museum of Space History. Retrieved 2008-06-29.
29. ^ "Makemake Becomes the Newest Dwarf Planet". Slashdot. July 13, 2008. Retrieved November 23, 2012.
30. ^ S. C. Tegler; W. M. Grundy; W. Romanishin; G. J. Consolmagno; et al. (2007-01-08). "Optical Spectroscopy of the Large Kuiper Belt Objects 136472 (2005 FY9) and 136108 (2003 EL61)". The Astronomical Journal. 133 (2): 526–530. arXiv:astro-ph/0611135. Bibcode:2007AJ....133..526T. doi:10.1086/510134.
31. ^ "Asteroid 136108 (2003 EL61)". HORIZONS Web-Interface. JPL Solar System Dynamics. Retrieved 2008-08-04.
32. ^ a b David Jewitt (February 2000). "Classical Kuiper Belt Objects (CKBOs)". University of Hawaii. Archived from the original on August 5, 2008. Retrieved 2008-08-04.
33. ^ Jane X. Luu & David C. Jewitt (2002). "Kuiper Belt Objects: Relics from the Accretion Disk of the Sun" (PDF). Annu. Rev. Astron. Astrophys. 40 (1): 63–101. Bibcode:2002ARA&A..40...63L. doi:10.1146/annurev.astro.40.060401.093818. Retrieved 2008-08-04.
34. ^ Levison, H. F.; Morbidelli, A. (2003-11-27). "The formation of the Kuiper belt by the outward transport of bodies during Neptune's migration". Nature. 426 (6965): 419–421. Bibcode:2003Natur.426..419L. doi:10.1038/nature02120. PMID 14647375.
35. ^ Preliminary simulation of Makemake (2005 FY9)'s orbit and the 2009-02-04 nominal (non-librating) rotating frame for Makemake. See (182294) 2001 KU76 for a proper 11:6 resonance libration.
36. ^ A. N. Heinze; D. deLahunta (2009). "The rotation period and light-curve amplitude of Kuiper belt dwarf planet 136472 Makemake (2005 FY9)". The Astronomical Journal. 138 (2): 428–438. Bibcode:2009AJ....138..428H. doi:10.1088/0004-6256/138/2/428.
37. ^ a b Parker, Alex (2016-05-02). "A Moon for Makemake". www.planetary.org.
38. ^ a b c J. Licandro; N. Pinilla-Alonso; M. Pedani; E. Oliva; et al. (2006). "The methane ice rich surface of large TNO 2005 FY9: a Pluto-twin in the trans-neptunian belt?". Astronomy and Astrophysics. 445 (3): L35–L38. Bibcode:2006A&A...445L..35L. doi:10.1051/0004-6361:200500219.
39. ^ M. E. Brown; E. L. Schaller; G. A. Blake (2015). "Irradiation products on the dwarf planet Makemake". The Astronomical Journal. 149 (3): 105. Bibcode:2015AJ....149..105B. doi:10.1088/0004-6256/149/3/105.
40. ^ S.C. Tegler; W.M. Grundy; F. Vilas; W. Romanishin; et al. (June 2008). "Evidence of N2-ice on the surface of the icy dwarf Planet 136472 (2005 FY9)". Icarus. 195 (2): 844–850. arXiv:0801.3115. Bibcode:2008Icar..195..844T. doi:10.1016/j.icarus.2007.12.015.
41. ^ Tobias C. Owen, Ted L. Roush, et al. (1993-08-06). "Surface Ices and the Atmospheric Composition of Pluto". Science. 261 (5122): 745–748. Bibcode:1993Sci...261..745O. doi:10.1126/science.261.5122.745. PMID 17757212.
42. ^ Lorenzi, V.; Pinilla-Alonso, N.; Licandro, J. (2015-05-01). "Rotationally resolved spectroscopy of dwarf planet (136472) Makemake". Astronomy & Astrophysics. 577: A86. arXiv:1504.02350. Bibcode:2015A&A...577A..86L. doi:10.1051/0004-6361/201425575. ISSN 0004-6361.
43. ^ Perna, D.; Hromakina, T.; Merlin, F.; Ieva, S.; Fornasier, S.; Belskaya, I.; Epifani, E. Mazzotta (2017-04-21). "The very homogeneous surface of the dwarf planet Makemake" (PDF). Monthly Notices of the Royal Astronomical Society. 466 (3): 3594–3599. Bibcode:2017MNRAS.466.3594P. doi:10.1093/mnras/stw3272. ISSN 0035-8711.
44. ^ "Dwarf Planet Makemake Lacks Atmosphere". ESO Press Release. Retrieved 23 November 2012.
45. ^ E.L. Schaller; M.E. Brown (2007-04-10). "Volatile Loss and Retention on Kuiper Belt Objects". The Astrophysical Journal. 659 (1): L61–L64. Bibcode:2007ApJ...659L..61S. doi:10.1086/516709.
46. ^ Keeter, Bill (2016-05-04). "Pluto's Interaction with the Solar Wind is Unique, Study Finds". NASA. Retrieved 2017-05-03.
47. ^ Beatty, Kelly (2016-03-25). "Pluto's Atmosphere Confounds Researchers". Sky & Telescope. Retrieved 2017-05-03.
48. ^ Parker, A. H.; Buie, M. W.; Grundy, W. M.; Noll, K. S. (2016-04-25). "Discovery of a Makemakean Moon". The Astrophysical Journal. 825 (1): L9. arXiv:1604.07461. Bibcode:2016ApJ...825L...9P. doi:10.3847/2041-8205/825/1/L9.
49. ^ McGranaghan, R.; Sagan, B.; Dove, G.; Tullos, A.; Lyne, J. E.; Emery, J. P. (2011). "A Survey of Mission Opportunities to Trans-Neptunian Objects". Journal of the British Interplanetary Society. 64: 296–303. Bibcode:2011JBIS...64..296M.