Makemake is a dwarf planet and perhaps the largest Kuiper belt object (KBO) in the classical population (cubewano) with a diameter that is probably about 2/3 the size of Pluto. Makemake has no known satellite, which makes it unique among the largest KBOs and means that it's mass can only be estimated.
Discovery
Makemake was discovered by the team of Mike Brown, Chad Trujillo and David Rabinowitz on March 31, 2005.
Despite its relative brightness (it is about a fifth as bright as Pluto), Makemake was not discovered until well 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.
Makemake 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.
Besides Pluto, Makemake is the only other dwarf planet that was bright enough for Clyde Tombaugh to have possibly detected 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, at an apparent magnitude of 16.0. 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.
Naming
Makemake was discovered just a few days after Easter and was nicknamed "Easterbunny." by the discovery team. Its official designation was 2005 FY9.
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 decided that, since the planet was discovered on Easter, to name it after Easter Island mythology over Roman Mythology, and thus the name Makemake was chosen.
Makemake, in the Rapa Nui mythology of Easter Island, was the creator of humanity, the god of fertility and the chief god of the "Tangata manu" or bird-man cult (this cult succeeded the island's more famous Moai era).
Stats
Estimated Diameter: 1440 km (1360 – 1480 km)
Aphelion: 53.07 AU
Perihelion: 38.51 AU
Semi-major axis: 45.79 AU
Orbital Period: 309.88 years
Rotation period: 7.77 hrs
Date discovered: 2005.3.31
Satellite: 0
Classification: Dwarf Planet, Kuiper Belt Object - Cubewano
Orbit
Makemake is classified a classical Kuiper belt object (Cubewano), which means its orbit lies far enough from Neptune to remain stable over the age of the Solar System. Cubewanos have perihelia further from the Sun and free from Neptune's perturbation.
Cubewanos 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 (29°) compared to others in that population.
Makemake is, probably coincidentally, near the 11:6 resonance with Neptune.
Brightness
Makemake is currently visually the second-brightest Kuiper belt object after Pluto, having a March opposition apparent magnitude of 16.7 in the constellation Coma Berenices. This is bright enough to be visible using a high-end amateur telescope.
Size
The size of Makemake is not precisely known, but the detection in infrared by the Spitzer space telescope and Herschel Space Telescope, combined with the similarities of spectrum with Pluto yielded an estimate of the diameter from 1,360 to 1,480 km. This makes Makemake possibly the third largest known trans-Neptunian object after Eris and Pluto.
Makemake is now designated the fourth dwarf planet in the Solar System because it has a bright V-band absolute magnitude of −0.44. This practically guarantees that it is large enough to achieve hydrostatic equilibrium and become an oblate spheroid.
Spectra and surface
Like 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 (CH4) absorption bands.
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 large amounts of ethane and tholins may be present as well, 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. While 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 which make up 3–7% of the surface.
Atmosphere
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: since 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 (30–35 K), which hinders its escape. The result of this process is a higher relative abundance of methane.
How big is it?
Makemake is so far away in the outer solar system that we don't know for sure how large it is. Because all we see is a dot of light, which is sunlight reflected off the surface of the dwarf planet. But we don't know if the object is bright because it is large or if it is bright because it is highly reflective or both.
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