Makemake ( minor-planet designation: 136472 Makemake) is a

dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit around the Sun, massive enough to be hydrostatic equilibrium, gravitationally rounded, but insufficient to achieve clearing the neighbourhood, orbital dominance like the ...

and the largest of what is known as the classical population of

Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

objects, with a diameter approximately that of Saturn's moon

Iapetus In Greek mythology, Iapetus (; ; ), also Japetus, is a Titan, the son of Uranus and Gaia and father of Atlas, Prometheus, Epimetheus, and Menoetius. He was also called the father of Buphagus and Anchiale in other sources. Iapetus was linked ...

, or 60% that of

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of Trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Su ...

. It has one known satellite. Its extremely low average temperature, about , means its surface is covered with

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

ethane Ethane ( , ) is a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...

, and possibly nitrogen ices. Makemake shows signs of geothermal activity and thus may be capable of supporting active geology and harboring an active subsurface ocean. 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 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 Easter Island (, ; , ) is an island and special territory of Chile in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. The island is renowned for its nearly 1,000 extant monumental statues, ...

, under the expectation by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(IAU) that it would prove to be a dwarf planet.

History

Discovery

Makemake was discovered on March 31, 2005, by a team at the

Palomar Observatory The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

, led by Michael E. Brown, 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 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, , was controversially announced on July 27 by a different team in Spain. The earliest known precovery observations of Makemake have been found in

photographic plate Photographic plates preceded film as the primary medium for capturing images in photography. These plates, made of metal or glass and coated with a light-sensitive emulsion, were integral to early photographic processes such as heliography, d ...

s of the Palomar Observatory's

Digitized Sky Survey The Digitized Sky Survey (DSS) is a digital data, digitized version of several photography, photographic astronomical surveys of the night sky, produced by the Space Telescope Science Institute between 1983 and 2006. Versions and source materia ...

from January 29, 1955 to May 1, 1998. Despite its relative brightness (a fifth as bright as Pluto), 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 ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

(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 Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth ...

, and the fact that it was at its farthest distance from the ecliptic at the time of its discovery, in the northern

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

of Coma Berenices. Makemake is the brightest trans-Neptunian object after

, with an apparent magnitude of 16.2 in late 1930, it is theoretically bright enough to have been discovered by Clyde Tombaugh, whose search for trans-Neptunian objects was sensitive to objects up to magnitude 17. Indeed, in 1934 Tombaugh reported that there were no other planets out to a magnitude of 16.5 and an inclination of 17 degrees, or of greater inclination but within 50 degrees of either node. And Makemake was there: At the time of Tombaugh's survey (1930–1943), Makemake varied from 5.5 to 13.2 degrees from the ecliptic, moving across Auriga, starting near the northwest corner of Taurus and cutting across a corner of Gemini. The starting position, however, was very close to the galactic anticenter, and Makemake would have been almost impossible to find against the dense background of stars. Tombaugh continued searching for thirteen years after his discovery of Pluto (and Makemake, though growing dimmer, was still magnitude 16.6 in early 1943, the last year of his search), but by then he was searching higher latitudes and did not find any more objects orbiting beyond Neptune.

Name and symbol

The provisional designation 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 Easter, also called Pascha ( Aramaic: פַּסְחָא , ''paskha''; Greek: πάσχα, ''páskha'') or Resurrection Sunday, is a Christian festival and cultural holiday commemorating the resurrection of Jesus from the dead, described in t ...

. In July 2008, in accordance with IAU rules for classical Kuiper belt objects, was given the name of a

creator deity A creator deity or creator god is a deity responsible for the creation of the Earth, world, and universe in human religion and mythology. In monotheism, the single God is often also the creator. A number of monolatristic traditions separate a ...

. The name of Makemake, the creator of humanity and god of fertility in the myths of the

Rapa Nui Easter Island (, ; , ) is an island and special territory of Chile in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. The island is renowned for its nearly 1,000 extant monumental statues, ...

, the native people of

, was chosen in part to preserve the object's connection with Easter.

Planetary symbol Planetary symbols are used in astrological symbol, astrology and traditionally in astronomical symbol, astronomy to represent a classical planet (which includes the Sun and the Moon) or one of the modern planets. The classical symbols were also use ...

s are no longer much used in astronomy. A Makemake symbol is included in

Unicode Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...

as U+1F77C: it is mostly used by astrologers, but has also been used by NASA. 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'. The commercial ''Solar Fire'' astrology software uses an alternative symbol (), a crossed variant of a symbol ( 16px) created by astrologer Henry Seltzer for his commercial software.

Orbit and classification

, Makemake was from the Sun, almost as far from the Sun as it ever reaches on its orbit. Makemake follows an orbit very similar to that of : highly inclined at 29° and a moderate

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of about 0.16. But still, Makemake's orbit is slightly farther from the Sun in terms of both the

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

and

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

. Its

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

is 306 years, more than Pluto's 248 years and Haumea's 283 years. Both Makemake and Haumea are currently far from the

(at an angular distance of almost 29°). Makemake will reach its

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

in 2033, whereas Haumea passed its aphelion in early 1992. Makemake is a classical Kuiper belt object (KBO), which means its orbit lies far enough from Neptune to remain stable over the age of the Solar System. Unlike

plutino In astronomy, the plutinos are a dynamical group of trans-Neptunian objects that orbit in 2:3 mean-motion resonance with Neptune. This means that for every two orbits a plutino makes, Neptune orbits three times. The dwarf planet Pluto is the la ...

s, which can cross Neptune's orbit due to their 2:3

resonance Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

with the planet, the classical objects have perihelia further from the Sun, free from Neptune's perturbation. 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. Makemake is, probably coincidentally, near the 13:7 resonance with Neptune.

Physical characteristics

Brightness, size, and rotation

Makemake is currently visually the second-brightest

object after

, having a March opposition

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 17.0 it will pass from its present

Coma Berenices to

Boötes Boötes ( ) is a constellation in the northern sky, located between 0° and +60° declination, and 13 and 16 hours of right ascension on the celestial sphere. The name comes from , which comes from 'herder, herdsman' or 'plowman' (literally, 'o ...

in November 2028. It is bright enough to be visible using a high-end

amateur An amateur () is generally considered a person who pursues an avocation independent from their source of income. Amateurs and their pursuits are also described as popular, informal, autodidacticism, self-taught, user-generated, do it yourself, DI ...

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

. Combining the detection in infrared by the Spitzer Space Telescope and Herschel Space Telescope with the similarities of Pluto's spectrum yielded an estimated diameter from 1,360 to 1,480 km. From the 2011 stellar occultation by Makemake, its dimensions had initially been measured at . However, the occultation data was later reanalyzed, leading to an estimate of without a pole-orientation constraint. Makemake was the fourth

recognized, because it has a bright V-band absolute magnitude of 0.05. Makemake has a highly reflective surface with a geometrical albedo of . The rotation period of Makemake is estimated at 22.83 hours. A rotation period of 7.77 hours published in 2009 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. This rotation period is relatively long for a dwarf planet. Part of this may be due to

tidal acceleration Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon) and the primary planet that it orbits (e.g. Earth). The acceleration causes a gradual recession of a satellite in a prograde orbit (satel ...

from Makemake's satellite. It has been suggested that a second large, undiscovered satellite might better explain the dwarf planet's unusually long rotation. Makemake's lightcurve amplitude is small, only 0.03 ''mag''. 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 tidal effects) is edge-on from Earth, implying that Makemake is being viewed equator-on.

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). The near-infrared spectrum is marked by the presence of the broad

(CH₄)

absorption band In spectroscopy, an absorption band is a range of wavelengths, frequency, frequencies or energies in the electromagnetic spectrum that are characteristic of a particular transition from initial to final state in a substance. According to quantum ...

s. Methane is observed also on Pluto and Eris, but its spectral signature is much weaker. Spectral analysis of Makemake's surface revealed that methane must be present in the form of large grains at least one centimetre in size. Large amounts of

and tholins, as well as smaller amounts of

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

acetylene Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is u ...

, and high-mass

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...

s (like

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

), may be present, most likely created by

photolysis Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons wi ...

of methane by solar radiation. 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 Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

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. The far-infrared (24–70 μm) and

submillimeter Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy that is conducted at submillimetre wavelengths (i.e., terahertz radiation) of the electromagnetic spectrum. Astronomers plac ...

(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. These studies were made before S/2015 (136472) 1 was discovered; thus, these small dark patches may have instead been the dark surface of the satellite rather than any actual surface features on Makemake. 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, byproducts 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. These results were 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 variations in the spectra were negligible, suggesting that Makemake's surface may indeed be homogenous. 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. More research shows that Eris,

and Makemake show signs of noticeable geothermal activity and could likely harbor active subsurface oceans. Rebuking the earlier speculations about distant celestial objects being uninhabitable.

Atmosphere

Makemake was expected to have an

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

similar to that of

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. The results showed that Makemake presently lacks a substantial atmosphere and placed an upper limit of 0.4–1.2 millipascals on the pressure at its surface. The presence of methane and possibly nitrogen suggests that Makemake could have a transient atmosphere similar to that of Pluto near its

. Nitrogen, if present, will be the dominant component of it. 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), which hinders its escape; the result of this process is a higher relative abundance of methane. However, studies of Pluto's atmosphere by ''

New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...

'' suggest that methane, not nitrogen, is the dominant escaping gas, suggesting that the reasons for Makemake's absence of nitrogen may be more complicated.

Satellite

Makemake has a single discovered moon, S/2015 (136472) 1 and nicknamed MK2. It was seen 21,000 km (13,000 mi) from the dwarf planet, and its diameter is estimated at (for an assumed albedo of 4%).

Exploration

Makemake was observed from afar by the ''

'' spacecraft in October 2007 and January 2017, from distances of 52 AU and 70 AU, respectively. 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. It has been calculated that a flyby mission to Makemake could take just over 16 years using a Jupiter

gravity assist A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby (spaceflight), flyby which makes use of the relative movement (e.g. orbit around the Sun) and gra ...

, based on a launch date of 24 August 2036. Makemake would be approximately 52 AU from the Sun when the spacecraft arrives.