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Makemake, minor-planet designation "136472 Makemake" is a dwarf planet and plutoid discovered on March 31, 2005 by astronomers Michael E. Brown, Chad Trujillo, and David Rabinowitz, and was announced on July 29 of the same year. It was confirmed as a dwarf planet on June 11, 2008. On April 26, 2016, a moon was discovered orbiting Makemake, given the temporary name S/2015 (136472) 1.

Makemake has an extremely low average temperature, around 30 K (-243 °C; -405 °F), one of the coldest in the Solar System. Its surface is likely covered with methane, ethane, and possibly nitrogen ices.

HistoryEdit

DiscoveryEdit

Makemake was initially discovered on March 31, 2005 by a team of astronomers at the Palomar Observatory, led by Michael E. Brown. It 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.

Despite its relative brightness (being about 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 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.

Along with 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. At the time of Tombaugh's survey, Makemake was only a few degrees from the ecliptic, near the border of Taurus and Auriga, with an apparent magnitude of 16.0. However, this position would have made it extremely difficult to find against the dense background of stars because it was very near the Milky Way. Tombaugh continued searching for some years after the discovery of Pluto although he was not able to find Makemake or any other trans-Neptunian objects.

NameEdit

When Makemake was made public, it was originally given the provisional designation 2005 FY9. The team used the codename "Easerbunny" because it was discovered shortly after Easter. In July 2008, in accordance with IAU rules for classical Kuiper belt objects, 2005 FY9 was given the name of a creator deity. It was named after Makemake, the creator of humanity and god of fertility in the myths of the Rapa Nui, the native people of Easter Island.

Orbit and classificationEdit

As of December 2015 Makemake is about 52.4 AU 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 Haumea, highly inclined at 29° and a moderate eccentricity of 0.16. The orbital period of Makemake is about 310 years, more than Pluto's 248 years and Haumea's 283 years. Both Makemake and Haumea are currently far from the ecliptic - the angular distance is almost 29°. Makemake is approaching its 2033 aphelion, whereas Haumea passed its aphelion in early 1982.

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 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. 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 11:6 resonance with Neptune.

Physical characteristicsEdit

Brightness, size and rotationEdit

Makemake is currently visually the second-brightest Kuiper belt object, after Pluto.

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 of 1,360 to 1,480 km. This means that Makemake is slightly larger than Haumea, making it likely the fourth-largest-known trans-Neptunian object after Pluto, Eris, and 2007 OR10, though the error bats with the latter overlap. Makemake was the fourth dwarf planet recognized, because it has a bright V-band absolute magnitude of -0.44.

The rotation period of Makemake is estimated at 7.77 hours. Its 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 tides resulting from its rapid rotation) is edge-on from Earth, implying that Makemake is really being viewed equator-on.

Spectra and surfaceEdit

As with Pluto, Makemake appears red in the visible spectrum, and significantly redder than the surface of Eris. The near-infrared spectrum is marked by the presence of the broad methane abosrption bands. Methane is also observed on Pluto and Eris, but its spectral signature is far 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. 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. 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.

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. 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. 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. 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.

AtmosphereEdit

Makemake was thought to have an atmosphere similar to Pluto's, but with a lower surface pressure. However, on April 23 2011 Makemake passed in front of an 18-th magnitude star and abruptly blocked its light. The results showed that Makemake currently lacks a substantial atmosphere and placed an upper limit of 4-12 nanobar 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 perihelion. 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 suggest that methane, not nitrogen, is the dominant escaping gas, suggesting that the reasons for Makemake's absence of nitrogen may be more complicated.