Makemake

Makemake (minor-planet number 136472) is a dwarf planet orbiting the Sun in the Kuiper belt, a disc of icy bodies beyond the orbit of Neptune. It is the fourth largest dwarf planet and trans-Neptunian object in the Solar System, having a diameter 60% that of Pluto. It was discovered on March 31, 2005, by American astronomers Michael E. Brown, Chad Trujillo, and David Rabinowitz at Palomar Observatory. As one of the largest outer Solar System objects found by this team, the discovery of Makemake contributed to the reclassification of Pluto as a dwarf planet in 2006. Makemake's surface is similar to that of Pluto: it is highly reflective, covered largely by frozen methane, and stained reddish-brown by tholins. Makemake has one known moon, which has not been named. The orbit of this moon suggests that Makemake's rotation has a high axial tilt, which implies that it experiences extreme seasons. Makemake shows evidence of geochemical activity and cryovolcanism, which has led scientists to suspect that it might harbor a subsurface ocean of liquid water. Gaseous methane has been detected around Makemake, although it is unclear whether it is contained in an atmosphere or comes from temporary outgassing. No high-resolution images of Makemake's surface exist because it has not been visited up close by a space probe.…

Makemake (minor-planet number 136472) is a dwarf planet orbiting the Sun in the Kuiper belt, a disc of icy bodies beyond the orbit of Neptune. It is the fourth largest dwarf planet and trans-Neptunian object in the Solar System, having a diameter 60% that of Pluto. It was discovered on March 31, 2005, by American astronomers Michael E. Brown, Chad Trujillo, and David Rabinowitz at Palomar Observatory. As one of the largest outer Solar System objects found by this team, the discovery of Makemake contributed to the reclassification of Pluto as a dwarf planet in 2006. Makemake's surface is similar to that of Pluto: it is highly reflective, covered largely by frozen methane, and stained reddish-brown by tholins. Makemake has one known moon, which has not been named. The orbit of this moon suggests that Makemake's rotation has a high axial tilt, which implies that it experiences extreme seasons. Makemake shows evidence of geochemical activity and cryovolcanism, which has led scientists to suspect that it might harbor a subsurface ocean of liquid water. Gaseous methane has been detected around Makemake, although it is unclear whether it is contained in an atmosphere or comes from temporary outgassing. No high-resolution images of Makemake's surface exist because it has not been visited up close by a space probe. Makemake is so far from Earth that it appears as a star-like point of light even when viewed through a telescope. Scientists have expressed desire to send a space probe to explore Makemake because of its geological activity and potential subsurface ocean. at Palomar Observatory (pictured).|alt=Palomar Observatory's 1.22-meter Samuel Oschin telescope was used to discover Makemake.]] plane.|alt=A diagram showing the orbits of Makemake and the outer planets. Makemake's orbit is much more tilted compared to the planets.]] Makemake orbits the Sun beyond Neptune at an average distance of 45.5 astronomical units (AU; ). It completes one orbit every 307 years. With an orbital eccentricity of 0.16, Makemake follows a moderately elliptical orbit that comes as close as to the Sun (perihelion) to as far as from the Sun (aphelion). Makemake has a relatively high orbital inclination of 29° with respect to the ecliptic. Makemake is currently near aphelion, the farthest point of its orbit. It is away from the Sun , and will reach aphelion in May 2033. Makemake is currently positioned far above the ecliptic and will remain so at aphelion, where its ecliptic latitude will be 25.9°. Makemake will cross the ecliptic in 2103 and will come to perihelion –26° below the ecliptic in 2186. N-body simulations show that Makemake's orbit is stable on a scale of billions of years and is unlikely to change significantly over the remaining life of the Solar System. Makemake shares its orbital characteristics with many other small icy bodies beyond Neptune, which together belong to a region known as the Kuiper belt. Makemake specifically belongs to the "dynamically hot" population of classical Kuiper belt objects, whose orbits have high inclinations (i > 5°), relatively low eccentricities (e 2 (about 3.6% Earth gravity) and its surface escape velocity is about  km/s.{{efn|name=escvel|The surface escape velocity in meters per second (m/s) is calculated according to v_{esc} = \sqrt{\frac{2GM}{r}} , where G is the gravitational constant, M is Makemake's mass in kilograms, and r is Makemake's radius in meters.}} spectrum of Makemake, as measured by the James Webb Space Telescope. The absorption signatures of methane ( ) at 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 ( ), acetylene ( ), deuterated methane ( ), and possibly ethylene ( ). |alt=A spectrum of Makemake plots its relative brightness over wavelengths of light. Dips in brightness at certain wavelengths represent absorption signatures caused by certain chemical compounds. In near-infrared wavelengths of light, Makemake's spectrum shows absorption signatures caused by frozen methane, ethane, acetylene, deuterated methane, gaseous methane, and possibly ethylene.]] Because of its great distance from the Sun, Makemake's surface has an extremely low temperature of —cold enough that some volatile substances like methane can exist as solid ice. 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. In visible light, the surface of Makemake appears very bright and reflective with a geometric albedo of 82% (more reflective than Pluto), suggesting that its methane is freshly deposited. Makemake's methane ice is highly absorbent in near-infrared, which indicates that it either exists in the form of unusually large, centimeter-sized pellets, or more likely, thick slabs of sintered particles. Meanwhile, phase curve measurements by the New Horizons spacecraft suggest that the regolith on Makemake's surface consists of smooth grains resembling snow. The long-chain hydrocarbons on Makemake's surface come from the irradiation of methane by ultraviolet sunlight and cosmic rays, which break down the methane and trigger photochemical reactions. These photochemical reactions can cascade: transforming methane into ethane, into ethylene, into acetylene, and so on until it leaves a dark, reddish mixture of complex hydrocarbons, called tholins. These tholins give Makemake a reddish-brownish color, similar to what has been seen on Pluto. Makemake is less red than Pluto, but is somewhat redder than Eris; the difference in color may be due to differing concentrations of tholins on these dwarf planets. Although tholins should darken the surface of Makemake, the dwarf planet remains bright because fresh methane ice covers up its tholins. 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. 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. Without nitrogen and carbon monoxide to mix with, methane ice on Makemake remains pure and can grow to large thicknesses or grain sizes. 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. 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. 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. 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.|alt=In Makemake's near-infrared spectrum, a series of brightness spikes is present. This is indicative of gaseous methane fluorescence.]] Analysis of JWST spectroscopy in 2025 revealed the presence of gaseous methane on Makemake, which fluoresces in near-infrared due to sunlight absorption. Makemake is the second trans-Neptunian object confirmed to have gas, after Pluto. 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 due to methane ice sublimation or cryovolcanic plumes. 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. 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. Such an extremely thin atmosphere was not detected in observations of Makemake's 2011 stellar occultation, which supports the occultation finding that Makemake lacks a substantial global atmosphere greater than 4–12 nanobars (0.4–1.2 millipascals). The temperature of this putative thin atmosphere would be about , 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. 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. Alternatively, if the methane gas detected by JWST is coming from outgassing only, then it would suggest that Makemake is releasing roughly of methane per second from 4–30% of its entire surface area. It is unknown if the methane is being outgassed at speeds fast enough to escape Makemake's gravity. If methane gas is escaping, it would form a comet-like coma surrounding Makemake. The estimated mass loss rate would be comparable to that of Enceladus's water plumes ( ) and the limited surface area of methane emission could potentially be related to Makemake's proposed cryovolcanic hotspot. Cryovolcanic outgassing of methane has been hypothesized to be ubiquitous among trans-Neptunian dwarf planets like Makemake. from April 2015. The moon was visible on April 27, but had moved and become hidden by April 29.|alt=Hubble Space Telescope images of Makemake's moon S/2015 (136472) 1 show it as a small gray dot positioned right next Makemake, which appears as a larger white dot.]] of 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.|alt=A time lapse of S/2015 (136472) 1 orbiting Makemake shows it moving back and forth about the dwarf planet. The back-and-forth motion of S/2015 (136472) 1 is due to its edge-on orbit from Earth's point of view.]] Makemake has only one known natural satellite or moon, which is unnamed with the provisional designation and unofficial nickname "MK 2". 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. 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 in order to explain some of Makemake's excess mid-infrared radiation. The moon follows a likely circular orbit around Makemake with an orbital period of 18 days and a semi-major axis of . When 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. Although this edge-on configuration made it difficult for telescopes to image , it may have allowed the moon to eclipse and occult Makemake. It is predicted that the moon may have eclipsed Makemake during 2009–2013, or may be still eclipsing Makemake during 2023–2027. No eclipses by have been reported . precovery image of Makemake (circled) above the large galaxy NGC 4274 on December 13, 2004|alt=A 2004 precovery image of Makemake shows it as a white dot amidst other white dots (stars) against the black backdrop of space.]] In terms of visual absolute magnitude, Makemake is the third intrinsically brightest known trans-Neptunian object, after Eris and Pluto. Makemake owes its high intrinsic brightness to its large size and highly reflective surface.{{efn|The absolute magnitude (H) of a Solar System body is calculated according to the equation H = -5\log_{10}{\left( \frac{D \sqrt{p} }{1329 \mathrm{km}} \right)} , which is rearranged from the original absolute magnitude and albedo (p) to diameter (D) equation D = \frac{1329 \mathrm{km}}{\sqrt{p}} \times 10^{-0.2H} given by Harris & Harris (1997). In the absolute magnitude equation, larger values for both diameter D and albedo p give a smaller (and thus brighter) value for H. Brown alludes to this relationship in his webpage describing the discovery of Eris, where he mentions that a dwarf planet can appear bright if it is either large, highly reflective, or both. Makemake is both large and highly reflective. }} In terms of visual apparent magnitude, on the other hand, Makemake is the second brightest trans-Neptunian object in the sky after Pluto, owing to its closer distance to the Sun than Eris. Makemake reaches a peak brightness of about apparent magnitude 17 when it comes to opposition during March to April, which is bright enough to be visible using a high-end amateur telescope. Because Makemake is very far from Earth, it appears very small with an angular diameter of about 38 milliarcseconds, so telescopes cannot resolve it beyond a star-like point of light. In the sky, Makemake is located in the northern constellation Coma Berenices and has been there since its discovery. In late 2028, Makemake will move to the constellation Boötes. Despite being one of the brightest trans-Neptunian objects, Makemake was discovered relatively late—well after the discoveries of many fainter trans-Neptunian objects. This is because Makemake follows a highly inclined orbit that brings it far outside the ecliptic—outside where previous sky surveys had mainly been searching. Although various sky surveys have serendipitously detected Makemake several years before its discovery, these observations (known as precoveries) were not recognized until after the fact. The earliest known precovery of Makemake comes from a photographic plate taken at Palomar Observatory on January 29, 1955, which predates Makemake's discovery by just over 50 years (16% of Makemake's orbital period). While moving across the sky, Makemake may pass in front of a background star and briefly block out its light from Earth's point of view, resulting in a stellar occultation. Stellar occultations by Makemake can reveal details such as its shape and potential atmosphere, but are difficult to accurately predict because the dwarf planet's great distance from Earth makes it subject to large uncertainties in its position. Stellar occultations by Makemake are rare because the dwarf planet is located in a region of the sky with relatively few stars. , only one stellar occultation by Makemake has been successfully predicted and detected by astronomers. The first and only observed stellar occultation by Makemake took place on April 23, 2011, which yielded 7 positive detections out of 16 participating telescopes located at sites scattered across South America. spacecraft on October 6, 2007|alt=Images of Makemake by the New Horizons spacecraft show it as a gray dot moving with respect to background stars against the black backdrop of space.]] Makemake has not been visited up close by a space probe, although astronomers and planetary scientists have expressed desire to send one there. Makemake has been recognized as an attractive exploration target because it potentially hosts a subsurface ocean with ongoing geological activity. The exploration of a trans-Neptunian object like Makemake would provide insights to the formation and evolution of the Solar System. A 2011 study by Ryan McGranaghan and colleagues 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 from the Sun when the spacecraft arrives. A 2024 study by the University of Tennessee suggested that if a flyby mission to Makemake made use of a powered Jupiter gravity assist, it could reach Makemake within a shorter time duration of 9.6–16.4 years, depending on the spacecraft's payload mass. A powered Jupiter gravity assist would be most optimal for launch dates of August 22, 2036 and September 27, 2048. A 2019 study by Amanda Zangari and collaborators identified several possible flyby trajectories to Makemake for different gravity assists and excess launch energies. For launch dates in 2036–2039, a single Jupiter gravity assist could bring a spacecraft to Makemake in 12.8–23.6 or 11.6–19.2 years, respectively. A single Saturn gravity assist may provide a faster route for lower-energy launches: for launch dates in 2032–2033 or 2036–2040, a spacecraft could reach Makemake in 19.2–22.5 or 12.8–19.1 years, respectively. For launch dates in 2037–2049, a spacecraft could reach Makemake in 16.8–17.3 years using gravity assists from both Jupiter and Saturn. 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. The spacecraft's outbound trajectory through the Kuiper belt permitted observations of Makemake at high phase angles that are otherwise unobtainable from Earth, which enabled the determination of the light scattering properties and phase curve behavior of Makemake's surface. ===Citations=== (r = distance from Sun in AU, rdot = radial velocity from the Sun in km/s) (Aphelion occurs when radial velocity or "rdot" changes from positive to negative. "hEcl-Lat" is the heliocentric ecliptic latitude, or angular distance above the ecliptic.) (Ecliptic crossing occurs when heliocentric ecliptic latitude or "hEcl-Lat" changes from positive to negative.) (Perihelion occurs when radial velocity or "rdot" changes from negative to positive. "hEcl-Lat" is the heliocentric ecliptic latitude, or angular distance above the ecliptic.) Ephemeris Type: Observer and Center: 500@399 (geocentric) (smaller values of H are brighter) 2012 Kavli Prize Laureate Lecture: Tales From the Outer Solar System by Michael E. Brown (video) Makemake Sky Charts and Coordinates – The Sky Live Precovery image with the 1.06-meter Kleť Observatory telescope on April 20, 2003 Makemake image by the Keck 1 Telescope on February 18, 2010 (Mike Brown)

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