Makemake

This article is about the dwarf planet. For the Rapa Nui god, see Makemake (deity). For other uses, see Makemake (disambiguation).

Makemake^[g] (minor-planet designation: 136472 Makemake) is a dwarf planet and the largest of what is known as the classical population of Kuiper belt objects,^[b] with a diameter of 1,430 kilometres (890 mi), or 60% that of Pluto.^[24] It has one known satellite, which has not been named. Its extremely low average temperature, between 30 and 40 K (−240 and −230 °C), means its surface is covered with frozen methane, which eventually breaks down into heavier organic compounds including ethane, ethylene, and acetylene.^[13] Makemake appears reddish-brown in color like Pluto,^[h] due to tholins on its surface. Makemake shows signs of geothermal activity and thus may be capable of supporting active geology and harboring an active subsurface ocean.^[25]

136472 Makemake

Low-resolution image of Makemake and its unnamed moon S/2015 (136472) 1 by the Hubble Space Telescope, April 2015
Discovery
Discovered by	Michael E. Brown Chad Trujillo David Rabinowitz
Discovery date	March 31, 2005
Designations
MPC designation	(136472) Makemake
Pronunciation	UK: /ˌmækiˈmæki/, US: /ˌmɑːkiˈmɑːki/ or /ˌmɑːkeɪˈmɑːkeɪ/ ⓘ[a]
Named after	Makemake
Alternative designations	2005 FY9
Minor planet category	Dwarf planet TNO classical (hot)[5] scattered-near[b]
Adjectives	Makemakean[6]
Symbol	(mostly astrological)
Orbital characteristics[7]
Epoch May 31, 2020 (JD 2458900.5)
Earliest precovery date	January 29, 1955
Aphelion	52.756 AU (7.8922 Tm)
Perihelion	38.104 AU (5.7003 Tm)
Semi-major axis	45.430 AU (6.7962 Tm)
Eccentricity	0.16126
Orbital period (sidereal)	306.21 yr (111,845 d)
Mean anomaly	165.514°
Inclination	28.9835°
Longitude of ascending node	79.620°
Time of perihelion	17 November 2186[8]
Argument of perihelion	294.834°
Known satellites	1 (S/2015 (136472) 1)
Physical characteristics
Dimensions	(1434+48 −18) × (1420+18 −24 km)[9]
Mean radius	715+19 −11 km[9]
Flattening	0.0098[c]
Surface area	6.42×106 km2[d][10]
Volume	1.53×109 km3[d][11]
Mass	(2.69±0.20)×1021 kg[12]
Mean density	1.67±0.17 g/cm3[12]
Equatorial surface gravity	0.35 m/s2[e]
Equatorial escape velocity	0.71 km/s[f][13]: 8
Sidereal rotation period	11.4133 h[14] or 22.8266±0.0001 h[14]
Axial tilt	46°–78° wrt orbit[6]: 4  63°–87° wrt ecliptic[6]: 3
Geometric albedo	0.82±0.02 (geometric)[14]: 7  0.74±0.06 (Bond)[15]: 23
Temperature	30–40 K[16][13]
Spectral type	B−V = 0.868±0.004[17] V−R = 0.449±0.003[17]
Apparent magnitude	17.0 (opposition)[18][19]
Absolute magnitude (H)	0.049±0.020 (corrected)[14] −0.12 (JPL)[7]

Makemake was discovered on March 31, 2005, by a team led by Michael E. Brown, and announced on July 29, 2005. It was initially known as 2005 FY₉ and later given the minor-planet number 136472. In July 2008, it was named after Makemake, a creator god in the Rapa Nui mythology of Easter Island, under the expectation by the International Astronomical Union (IAU) that it would prove to be a dwarf planet.^{[26][27][28][29]}

History

Discovery

Makemake was discovered on March 31, 2005, by a team at the Palomar Observatory, led by Michael E. Brown,^[7] 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.^[30]

The earliest known precovery observations of Makemake have been found in photographic plates of the Palomar Observatory's Digitized Sky Survey from January 29, 1955 to May 1, 1998.^[31]

Despite its relative brightness (a fifth as bright as Pluto),^[i] 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.^[19]

Name and symbol

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.^[1]

In July 2008, in accordance with IAU rules for classical Kuiper belt objects, 2005 FY₉ was given the name of a creator deity.^[33] 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,^[28] was chosen in part to preserve the object's connection with Easter.^[1]

Planetary symbols are no longer much used in astronomy. A Makemake symbol ⟨⟩ is included in Unicode as U+1F77C:^[34] it is mostly used by astrologers,^[35] but has also been used by NASA.^[36] The symbol was designed by Denis Moskowitz and John T. Whelan; it is a traditional petroglyph of Makemake's face stylized to resemble an 'M'.^[37] The commercial Solar Fire astrology software uses an alternative symbol (),^[35] a crossed variant of a symbol () created by astrologer Henry Seltzer for his commercial software.

Orbit and classification

Diagram showing Makemake's inclined orbit (gray) around the Sun, with the outer planets shown. The vertical gray lines along Makemake's orbital path mark its positions above and below the ecliptic plane.

As of April 2019^[update], Makemake was 52.5 AU (7.85 billion km) from the Sun,^[18][19] almost as far from the Sun as it ever reaches on its orbit.^[21] Makemake follows an orbit very similar to that of Haumea: highly inclined at 29° and a moderate eccentricity of about 0.16.^[38] But still, Makemake's orbit is slightly farther from the Sun in terms of both the semi-major axis and perihelion. Its orbital period is 306 years,^[7] more than Pluto's 248 years and Haumea's 283 years. Both Makemake and Haumea are currently far from the ecliptic (at an angular distance of almost 29°). Makemake will reach its aphelion in 2033,^[19] whereas Haumea passed its aphelion in early 1992.^[39]

Makemake is a classical Kuiper belt object (KBO),^[40][b] which means its orbit lies far enough from Neptune to remain stable over the age of the Solar System.^[41][42] 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.^[41] 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.^[5] Makemake is, probably coincidentally, near the 13:7 resonance with Neptune.^[43]

Size, shape, and mass

Comparison of sizes, albedos, and colors of various large trans-Neptunian objects with diameters greater than 700 km (430 mi). Makemake is shown on the top row, second from the right. The dark colored arcs represent uncertainties of the object's size.

Makemake is a nearly spherical object with an average diameter of 1,430 km (890 mi),^[9]: 2 which is about 60% (3⁄5) the diameter of Pluto^[j][24] or 11% (1⁄9) the diameter of Earth.^[45] In terms of diameter, Makemake is the fourth largest known dwarf planet and trans-Neptunian object in the Solar System, after Pluto, Eris, and Haumea.^[46] Observations of a stellar occultation in 2011 showed that Makemake is slightly oblate or flattened at its poles, with a polar diameter of up to 1,420 km (880 mi)^[k] and an equatorial diameter of 1,434 km (891 mi).^[9] This flattened spherical shape is known as an oblate spheroid (or more technically, a Maclaurin spheroid); Makemake is rounded by own gravity via hydrostatic equilibrium, whereas its rotation bulges out its equator.^{[9]: 2 [14]: 5 [16]: 12}

Makemake has mass of around 2.69×10²¹ kg (with an uncertainty of ±0.20×10²¹ kg), which was determined from the orbital period and distance of its moon.^[12]: 3 This makes Makemake the fourth most massive known dwarf planet and trans-Neptunian object in the Solar System, again after Eris, Pluto, and Haumea.^[47] Compared to other Solar System objects, Makemake is about 3.7% the mass of Earth's Moon (or 0.045% Earth's mass)^[l] or around 20% Pluto's mass.^[m] Given Makemake's mass and average diameter, its average surface gravity is about 0.35 m/s^2[e] and its surface escape velocity is about 0.71 km/s.^[f][13]: 8

Rotation

The rotation period of Makemake is uncertain, with measurements giving either 11.4 or 22.8 hours (0.48 or 0.95 d) as of 2025^[update].^{[16]: 2, 7} These rotation period measurements were made by monitoring changes in Makemake's brightness over time, which is plotted as a light curve.^{[14][16]: 2} Makemake exhibits very little variation in brightness (0.03 magnitudes) presumably due to small albedo variations across its surface, which makes it difficult for telescopes to measure Makemake's light curve and rotation period.^{[14]: 1, 6} For example, studies prior to 2019 have suggested possible rotation periods of 7.77, 11.24, 11.5, or 22.48 hours.^[14]: 1 For measurements as of 2025^[update], it is unclear whether Makemake's brightness peaks once or twice during one rotation, so it is ambiguous whether the rotation periods of 11.4 hours or its double value 22.8 hours are correct.^[16]: 2

The axial tilt of Makemake has not been measured, although it can be reasonably assumed that its rotation axis is aligned with the orbital plane of its moon.^{[6]: 4 [49]: 16} In that case, Makemake would have a high axial tilt somewhere between 46° and 78° with respect to its orbit around the Sun (or 63°–87° with respect to the ecliptic), with its equator facing toward the Sun and Earth (near equinox) at the time its moon was discovered.^[6]: 3–4 This high axial tilt together with Makemake's eccentric orbit can give rise to major seasonal changes, similar to those seen on Pluto.^{[6]: 4–5 [49]: 16} Makemake's moon was predicted to eclipse Makemake sometime during 2009–2013 or 2023–2027, so Makemake may have passed equinox during either of those year ranges if its rotation is aligned with its moon's orbit.^[12]: 1

Geology

Surface

The near-infrared spectrum of Makemake, as measured by the James Webb Space Telescope. The absorption signatures of methane (CH
₄) at 1–2 μm are very prominent in Makemake's spectrum, which indicates it is very abundant on Makemake's surface. Other chemical compounds detected on Makemake include ethane (C
₂H
₆), acetylene (C
₂H
₂), deuterated methane (CH
₃D), and possibly ethylene (C
₂H
₄).^[13]: 2

An artistic illustration of Makemake depicting its uniform, light brown surface and lack of a substantial atmosphere

Because of its great distance from the Sun, Makemake's surface has an extremely low temperature of 30 to 40 K (−243 to −233 °C; −406 to −388 °F),^{[16]: 5 [13]: 17}—cold enough that some volatile substances like methane can exist as solid ice.^[50] Astronomical spectroscopy has shown that the surface of Makemake is dominated by frozen methane, with smaller amounts of long-chain hydrocarbons including ethane, ethylene, acetylene, and various high-mass alkanes like propane.^{[51][13]: 2} In visible light, the surface of Makemake appears very bright and reflective with a geometric albedo of 82% (more reflective than Pluto),^{[14]: 7 [15]: 5} suggesting that its methane is freshly deposited.^{[49]: 15 [52]: 3–4} Makemake's methane ice is highly absorbant in near-infrared, which indicates that it either exists in the form of unusually large, centimeter-sized pellets, or thick slabs of sintered particles.^{[45][53]: 3597 [52]: 16} Planetary scientists consider the second option more likely.^{[53]: 3597 [52]: 16} It is estimated that methane ice makes up roughly 80% of Makemake's surface composition, with the remaining 20% attributed to long-chain hydrocarbons.^[51]: 2

The long-chain hydrocarbons on Makemake's surface come from the irradiation of methane by ultraviolet sunlight and cosmic rays, which breaks down the methane and triggers photochemical reactions.^{[51]: 1 [13]: 2, 9} These photochemical reactions can cascade: transforming methane into ethane, into ethylene, into acetylene, and so on^{[53]: 3594–3595} until it leaves a dark, reddish mixture of complex hydrocarbons, called tholins.^{[21]: 285 [52]: 4} These tholins give Makemake a reddish-brownish color,^[h] similar to what has been seen on Pluto.^[45][55] Makemake is less red than Pluto, but is somewhat redder than Eris;^[15]: 5 the difference in color may be due to differing concentrations of tholins on these dwarf planets.^[17]: 5475 Although tholins should darken the surface of Makemake, the dwarf planet remains bright because fresh methane ice covers up its tholins.^{[58]: 569 [49]: 15 [52]: 3–4}

Makemake shares its high abundance of methane ice with Pluto and Eris, but unlike those two, Makemake apparently lacks both carbon monoxide and nitrogen ices.^{[52]: 1–2} The James Webb Space Telescope (JWST) could not find these two ices in Makemake's surface, indicating that it contains less than 3% nitrogen and less than 1 part per million of carbon monoxide.^{[52]: 13 [13]: 1} Without nitrogen and carbon monoxide to mix with, methane ice on Makemake remains pure and can grow to large thicknesses or grain sizes.^{[21]: 288 [52]: 16} Makemake's lack of nitrogen is expected, because nitrogen is highly volatile and its vapor can escape from Makemake's gravity more easily than from the stronger gravities of Pluto and Eris.^{[50]: 287 [49]: 16 [52]: 18} The reason for Makemake's apparent lack of carbon monoxide is less clear: it could have been removed via either atmospheric escape or hydrothermally-driven geochemical reactions inside Makemake, or Makemake could have somehow formed with low amounts of carbon monoxide.^{[52]: 19 [59]: 10 [60]: 5} Water and carbon dioxide ices are also apparently absent in Makemake's surface, even though they are common refractory (non-volatile) materials in Kuiper belt objects; this may be because on Makemake, these ices are completely covered by volatile material like methane and its irradiation products.^{[53]: 3598 [59]: 13}

Makemake appears to have a uniform surface with very small longitudinal variations in albedo, color, and composition,^{[61][53][14]: 1, 6} in contrast to the highly mottled terrain of Pluto.^[49]: 16 It is unknown whether Makemake shows latitudinal surface variations, as detecting these would require continuous observations of Makemake changing its aspect angle^[n] as it orbits the Sun (in other words, change seasons), which takes many years.^{[14]: 6–7 [16]: 8} Makemake showed no change in its absolute magnitude and light curve from 2006 to 2017, during which Makemake's aspect angle changed by about 11°.^[14]: 7 If Makemake has latitudinal surface variations, they would likely resemble bands running longitudinally across Makemake's surface.^[49]: 16 Planetary scientists William M. Grundy, Alex H. Parker, and colleagues have hypothesized that Makemake's abundant volatile methane may lead to similar geography and geology as Pluto.^{[49]: 16 [52]: 4} If Makemake has seasonal volatile transport processes like Pluto, it could potentially produce a longitudinally uniform band of dark material, akin to Pluto's Belton Regio.^[49]: 16 Alternatively, if Makemake has a non-global atmosphere that froze onto its surface, its equator could be bright and frost-covered, whereas its poles could be darker.^[49]: 16 Seasonal sublimation and deposition of methane could potentially produce bladed terrain or even thick, convecting glaciers resembling Pluto's Sputnik Planitia.^[52]: 4 Makemake is not expected to have mountains taller than 10 km (6.2 mi).^[14]: 6

Interior and possible geological activity

Makemake has a bulk density of about 1.67 g/cm³ (with an uncertainty of ±0.17 g/cm³),^[12]: 3 similar to the trans-Neptunian dwarf planets Pluto, Gonggong, and Quaoar.^[47]: 7 Like for these dwarf planets, this density suggests that Makemake has an interior mostly made of water ice and rock.^{[47]: 7 [62]: 10} Makemake is large enough that its interior is likely differentiated, having a rocky core surrounded by layers of ice.^{[63]: 230 [64][62]: 8} Planetary scientists suspect that Makemake's interior contains enough radionuclides and primordial heat to sustain a subsurface liquid water ocean, in the past or potentially even today.^[62][65] A high amount of heat inside Makemake could give rise to geological phenomena such as cryovolcanism.^{[66][16]: 4}

Spectroscopy by the JWST has detected heavy isotopologues of methane containing deuterium (D or ²H) and carbon-13 (¹³C) in Makemake's surface, for which astronomers have determined a deuterium-to-hydrogen (D/H) ratio of (2.9±0.6)×10⁻⁴ and a ¹³C/¹²C ratio of 0.010±0.003.^[52] While Makemake's ¹³C/¹²C ratio matches those of other Solar System objects, Makemake's D/H ratio is different: it is much lower than the D/H ratios of methane in comets, but is similar to the D/H ratios of water in comets.^[52][67] Planetary scientists have interpreted Makemake's low D/H ratio as evidence for Makemake having a warm interior with active hydrothermal geochemistry: Makemake's deuterium-poor methane may have inherited its hydrogen from geochemical reactions in subsurface water, which require high temperatures of 150 °C (302 °F) that could only be sustained by heat from Makemake's putative core.^[67][62] In this scenario, Makemake's subsurface water may either exist in the form of liquid water or convecting solid ice, and internally-produced methane may have been transported to Makemake's surface via outgassing or cryovolcanic eruptions.^[62] However, it is still possible that Makemake's deuterium-poor methane may be primordial (originating directly from the protosolar nebula via accretion), so internal geochemical activity may not be necessary to explain its existence.^[60]

Makemake emits an unusually high amount of mid-infrared radiation compared to far-infrared, which has received various interpretations by astronomers since its first reported detection by the Spitzer Space Telescope in 2008.^[16]: 1 Astronomers initially thought that Makemake's excess mid-infrared emission came from patches of dark, warm terrain mixed with bright, cold terrain (and also from its moon after it was discovered), but this hypothesis could not accurately describe Makemake's infrared emission at different wavelengths,^{[16]: 1–2} nor could it explain Makemake's minimal brightness variability.^[68] In 2025, Csaba Kiss and collaborators proposed that Makemake's excess mid-infrared emission could instead be caused by either a cryovolcanic hotspot reaching temperatures of about 150 K (−123 °C; −190 °F), or an orbiting ring consisting of tiny carbonaceous dust grains.^{[16]: 1–2 [65]} The cryovolcanic hotspot scenario is favored because the aforementioned dust ring would quickly destabilize due to solar radiation pressure, although the ring could potentially be replenished if cryovolcanic eruptions could eject carbonaceous dust into orbit around Makemake.^[16]: 6 The proposed cryovolcanic hotspot may be emitting a similar amount of heat energy as the south pole geysers of Saturn's moon Enceladus, and it could potentially erupt cryolavas containing ammonia and various salts dissolved in liquid water.^{[16]: 4 [65]} The location of this cryovolcanic hotspot on Makemake's surface is unknown, though it is estimated to cover an area of about 350 km² (140 sq mi; equivalent to a ~10 km or 6.2 mi-radius circle).^{[16]: 3–4}

Atmosphere or outgassing

JWST detection of gaseous methane (CH
₄) fluorescence in Makemake's near-infrared spectrum (left panel, labeled a). Either an outgassing methane coma (b) or a thin methane atmosphere (c) can explain the observed fluorescence.

Analysis of JWST spectroscopy in 2025 has revealed the presence of gaseous methane on Makemake, which fluoresces in near-infrared due to sunlight absorption.^[69][13] Makemake is the second trans-Neptunian object confirmed to have gas, after Pluto.^[13][69] However, it is uncertain whether Makemake's methane gas is contained in a gravitationally bound atmosphere, or is temporarily outgassing (if not escaping) from its surface via methane ice sublimation or cryovolcanic plumes.^{[13]: 1 [69]} Makemake is barely massive and cold enough to theoretically hold onto an atmosphere of methane or nitrogen; JWST observations have shown that Makemake does not appear to have nitrogen gas, which indicates most of it had already been lost to atmospheric escape.^[13]: 17

If Makemake's detected methane gas is entirely contained in a gravitationally bound atmosphere, then the surface atmospheric pressure would be roughly 10 picobars (1 micropascal), which is 100 billion times less than Earth's atmospheric pressure and 1 million times less than Pluto's.^[69] Such an extremely thin atmosphere was not detected in observations of Makemake's 2011 stellar occultation, which supports earlier conclusions that Makemake lacks a substantial global atmosphere greater than 4–12 nanobars (0.4–1.2 millipascals).^{[13]: 9 [58][53]} The temperature of this putative thin atmosphere would be about 40 K (−233.2 °C; −387.7 °F), which is slightly above the sublimation temperature of methane at this atmosphere's surface pressure. This raises the possibility that Makemake's putative atmosphere may be sustained by the sublimation of surface methane ice.^{[69][13]: 9} As Makemake follows an eccentric orbit, its putative atmosphere may change with distance from the Sun: for example, in the warmer temperatures of perihelion, Makemake may sublimate more methane but may lose some to atmospheric escape.^[50]: L62

Alternatively, if the methane gas detected by JWST is coming from outgassing only, then Makemake would be releasing roughly 266 kg (586 lb) of methane per second from 4–30% of its entire surface area.^[13]: 9 It is unknown if the methane is being outgassed at speeds fast enough to escape Makemake's gravity; if it is escaping, it would form a comet-like gas coma surrounding Makemake.^[13]: 8 The estimated mass loss rate would be comparable to that of Enceladus's water plumes (300 kg/s or 660 lb/s) and the limited surface area of methane emission could be potentially related to Makemake's proposed cryovolcanic hotspot.^[13]: 9 Cryovolcanic outgassing of methane has been hypothesized to be ubiquitous among large trans-Neptunian dwarf planets like Makemake.^[70]: 5

Satellites and potential rings

S/2015 (136472) 1

Main article: S/2015 (136472) 1

Discovery images of Makemake's moon by the Hubble Space Telescope from April 2015. The moon was visible on April 27, but had moved and become hidden by April 29.

Animated time lapse of S/2015 (136472) 1 orbiting Makemake, as seen by Hubble during 2018–2019. Makemake appears smudged because its glare has been digitally removed to make the moon more visible.

Makemake has only one known natural satellite or moon, which is unnamed with the provisional designation S/2015 (136472) 1 and unofficial nickname "MK2".^[6][64] It was discovered by astronomers Alex H. Parker, Marc W. Buie, William M. Grundy, and Keith S. Noll in Hubble Space Telescope images taken on April 27, 2015, and was announced on April 26, 2016.^[71] S/2015 (136472) 1 is about 1,300 times (7.8 magnitudes) fainter than Makemake in visible light and is suspected to have a very dark surface with a diameter of 175 km (109 mi) in order to explain some of Makemake's excess mid-infrared radiation.^{[68][6]: 3–4} The moon follows a likely circular orbit around Makemake with an orbital period of 18 days and a semi-major axis of 22,250 ± 780 km (13,830 ± 480 mi).^[12]

When S/2015 (136472) 1 was discovered, its orbit was oriented nearly edge-on from the point of view of Earth-based observatories, which meant that the moon appeared to pass in front of or behind Makemake.^{[6]: 2 [12]: 3} Although this edge-on configuration made it difficult for telescopes to image S/2015 (136472) 1,^[68] it may have allowed the moon to eclipse and occult Makemake.^{[6]: 4 [64]} Although eclipses by S/2015 (136472) 1 have not been observed, it is predicted that the moon may have eclipsed Makemake during 2009–2013, or may be still eclipsing Makemake during 2023–2027.^[12]: 1

Makemake system

Name	Diameter (km)	Semi-major axis (km)	Discovery date
Makemake	1430+38 −22		March 31, 2005
S/2015 (136472) 1	≈ 175	22250±780	April 27, 2015

Possibility of other satellites

Imaging observations by the Hubble Space Telescope indicate Makemake does not have additional moons brighter than apparent magnitude 26.9 (~10 magnitudes fainter than Makemake)^[o] at distances beyond 30,000 km (19,000 mi).^[72]: 8 Larger moons could be hidden if they orbited very close to Makemake.^[14]: 6 The possibility of Makemake having an additional dark moon larger than S/2015 (136472) 1 was discussed by astronomers as a potential solution for Makemake's excess mid-infrared emission and apparently slow rotation,^[14]: 6 but it was disfavored because it required an unrealistically large moon size.^[16]: 3

Possibility of rings

Makemake is not known to have rings. Rings around distant objects are too small to be directly imaged by telescopes, so they would ideally be detected in observations of stellar occultations.^[73]: 27 However, rings were not detected in Makemake's stellar occultation from 2011. If rings do exist around Makemake, they would likely orbit around its equator in an edge-on configuration like S/2015 (136472) 1, which could have made them missable to astronomers during the 2011 occultation.^[16]: 5 The possibility of a ring around Makemake has been explored as a potential solution to Makemake's excess mid-infrared emission, but it was deemed unlikely because the hypothesis would require the ring to be made of extremely small (~100 nm) dust particles, which would make it vulnerable to destruction by solar radiation pressure within a decade.^{[16]: 6, 15} Nevertheless, it might be possible for Makemake to sustain such a ring if it has shepherd moons, a continuous production of dust from colliding particles and small moons, or cryovolcanic eruptions ejecting dust into orbit.^[16]: 6

Origin

Like other dwarf planets in the Kuiper belt, Makemake is believed to have formed early in the Solar System's history,^[45][74] within 10 million years after the formation of the Sun's protosolar nebula approximately 4.57 billion years ago.^{[63]: 214 [75]: 176} Makemake presumably begun as a planetesimal that grew to its present-day size by accreting surrounding material and other planetesimals until the protosolar nebula dissipated within a few million years.^[63]: 214 The temperature of Makemake's formation environment must have been cold enough for volatiles such as methane to condense into solids and subsequently accrete into the dwarf planet,^{[52]: 3, 17 [60]: 3} although it is likely that Makemake lost some of its primordial methane during accretion, when it had a smaller mass and was experiencing warming by large impacts and its closer distance to the Sun.^[62]: 9

According to a 2020 hypothesis based on Solar System formation models (an update of the Nice model from 2005 that first proposed a similar scenario), a few tens of millions of years after the protosolar nebula's formation, gravitational interactions among the giant planets caused Neptune to abruptly migrate outward into a massive circumstellar disk between 15 and 30 AU from the Sun, gravitationally scattering many of the objects within it.^{[76][75]: 176} The model indicates that nearly all Kuiper belt objects including Makemake originally formed closer to the Sun than where they are now, in that circumstellar disk.^{[75]: 175–176} Makemake was among the objects scattered by Neptune and ended up on a highly inclined and eccentric orbit far from the Sun—located in what is now known as the "hot" classical Kuiper belt.^{[75]: 176 [p]} The existence of Makemake's moon S/2015 (136472) 1 suggests that the dwarf planet may have experienced a massive collision with another body sometime in its history, as has been hypothesized for other dwarf planets with moons.^[64]

Exploration

New Horizons

Makemake, indicated with red bars, as imaged by the New Horizons spacecraft in October 2007

Makemake was observed from afar by the New Horizons spacecraft in October 2007 and January 2017, from distances of 52 AU and 70 AU, respectively.^[15] The spacecraft's outbound trajectory permitted observations of Makemake at high phase angles that are otherwise unobtainable from Earth, enabling the determination of the light scattering properties and phase curve behavior of Makemake's surface.^[15]

Proposed

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 August 24, 2036. Makemake would be approximately 52 AU from the Sun when the spacecraft arrives.^[77]

See also

• Astronomical naming conventions
• Clearing the neighbourhood
• International Astronomical Union
• Planets beyond Neptune
• Ocean worlds
• Extraterrestrial liquid water

Notes

1. The Rapa Nui pronunciation is [ˈmakeˈmake], which is anglicized as /ˈmækiˈmæki/ in the UK and /ˈmɑːkiˈmɑːki/^[1] as well as /ˈmɑːkeɪˈmɑːkeɪ/ in the US.^[2][3] The distinction between /ɑː/ and /æ/ reflect how the US and UK handle the Polynesian 'a' (parallel to the first 'a' in Italian 'pasta'); the /eɪ/ pronunciation attempts to approximate the Polynesian 'e', and is used by Brown and his students.^[4]
2. 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.^{[20][21][22][23]}
3. Calculated using (a−b)/a and the dimensions from Brown^[9]
4. Calculated using the dimensions from Brown^[9] assuming an oblate spheroid.
5. The surface gravity in meters per second squared (m/s²) is calculated according to ${\displaystyle {\frac {GM}{r^{2}}}}$, where G = 6.6743×10⁻¹¹ m³⋅kg⁻¹⋅s⁻²‍^[48] is the gravitational constant, M is Makemake's mass in kilograms, and r is Makemake's radius in meters.
6. The surface escape velocity in meters per second (m/s) is calculated according to ${\displaystyle v_{esc}={\sqrt {\frac {2GM}{r}}}}$, where G = 6.6743×10⁻¹¹ m³⋅kg⁻¹⋅s⁻²‍^[48] is the gravitational constant, M is Makemake's mass in kilograms, and r is Makemake's radius in meters.
7. Pronounced as four syllables, with stress on the a's. Values of the vowels vary; see info-box.
8. In planetary astronomy, the term "red" is used to describe objects that reflect more light at longer (redder) wavelengths.^[54]: 145 Astronomers have described Makemake and Pluto as similarly "red",^{[55]: L38 [56]: 437} although it is known that Pluto appears more of a brown color (not literally red) to the human eye.^[57]
9. It has an apparent magnitude at opposition of 16.7 vs. 15.1 for Pluto.^[32]
10. Pluto has a radius of 1188 km, or a diameter of 2376 km.^[44] Dividing Makemake's radius by Pluto's radius gives the fraction of Pluto's radius (0.602 R_P), which can be converted to a percentage by multiplying by 100.
11. The exact flattening and tilt of Makemake's poles with respect to Earth's line of sight is not known, so the apparent polar diameter of 1420+18
    −24 km from the 2011 occultation only represents an upper limit to Makemake's true polar diameter. This is because in a stellar occultation, only the occulting object's shadow is seen.^[9]
12. Earth has a mass of 5.9722×10²⁴ kg and its Moon has a mass of 7.346×10²² kg. Dividing Makemake's mass by these aforementioned mass values gives the fraction of Earth's mass (0.00045 M_🜨) and Moon's mass (0.037 M_☾), respectively. These decimal values converted to percentages by multiplying by 100.
13. Pluto has a mass of 1.303×10²² kg^[44] Dividing Makemake's mass by Pluto's mass gives the fraction of Pluto's mass (0.206 M_P), which can be converted to a percentage by multiplying by 100.
14. The aspect angle of a Solar System object is defined as the angle between the object's rotation axis and Earth's line of sight to the object.^[78]
15. The size of an object with a known brightness depends on its albedo. If a satellite 10 magnitudes fainter than Makemake has an albedo of 0.7, its diameter would be roughly 16 km (9.9 mi).^[72]: 8 A smaller albedo would correspond to a larger diameter.
16. "Hot" in this case does not indicate temperature (Makemake is very frigid), but the dynamics of its orbit, which is highly perturbed.