Makemake

Makemake (designated 136472) is classified as a dwarf planet, a category established by the International Astronomical Union (IAU) in 2006. This classification signifies that it is massive enough to be rounded by its own gravity but has not cleared the neighborhood around its orbit. Makemake is a prominent member of the Kuiper Belt, a vast circumstellar disc of icy bodies extending from Neptune's orbit to roughly 50 AU from the Sun.

More specifically, its eccentric orbit suggests it may also be considered part of the scattered disk, a region of TNOs with orbits that are more inclined and eccentric than those in the main Kuiper Belt. Its estimated diameter is around 1,430 kilometers (890 miles), making it one of the largest known dwarf planets, comparable in size to Pluto and Eris. Spectroscopic analysis reveals a surface rich in methane ice, similar to Pluto, which contributes to its reddish hue and low albedo, meaning it reflects only a small fraction of the sunlight it receives.

Makemake was discovered on March 31, 2005, by the astronomical team of Michael Brown, Chad Trujillo, and David Rabinowitz using the Palomar Observatory. Its discovery was part of an ongoing effort to survey the outer solar system for large trans-Neptunian objects (TNOs). The discovery of Makemake, along with Eris and Haumea, was instrumental in prompting the IAU to formally define the term 'planet' and establish the category of 'dwarf planet.' This reclassification led to Pluto being reclassified as a dwarf planet.

The object was initially given the provisional designation 2005 FY9. Following IAU guidelines for naming dwarf planets after creation deities, it was eventually named Makemake, after the creator god of the Rapa Nui people of Easter Island. This naming choice reflects the object's remote and significant nature, linking it to a culture that has a deep connection to celestial observation.

Makemake's surface is predominantly composed of methane ice, with possible traces of ethane and tholins, which are complex organic molecules formed by ultraviolet radiation acting on methane. This composition gives Makemake its characteristic reddish-brown color. The surface temperature is extremely low, estimated to be around 30-300 Kelvin (-243 to -43 degrees Celsius), or approximately -380 to -43 degrees Fahrenheit.

The presence of methane ice suggests that Makemake has a tenuous atmosphere, which may freeze out and fall to the surface during its aphelion (farthest point from the Sun). The discovery of its moon, S/2015 (136472) 1, in 2015 was crucial. This moon's orbit allowed astronomers to calculate Makemake's mass with greater precision, estimated to be about 3.1 x 10^21 kg.

This mass is essential for understanding its gravitational influence and its role in the dynamics of the Kuiper Belt.

Makemake follows a highly eccentric and inclined orbit around the Sun, taking approximately 306 Earth years to complete a single revolution. Its orbital semi-major axis is about 42.4 AU, but its eccentricity of 0.16 causes its distance from the Sun to vary significantly, ranging from about 35.8 AU at perihelion to 49.0 AU at aphelion. Its orbital inclination is about 29 degrees.

These orbital parameters place Makemake within the Kuiper Belt, but its characteristics also suggest it might be a member of the scattered disk, a population of icy bodies with orbits that have been perturbed by Neptune. Studying Makemake's orbit helps scientists understand the long-term stability of the Kuiper Belt and the gravitational interactions within the outer solar system. Its existence and properties provide vital data for models of solar system formation and evolution, offering insights into the conditions of the protoplanetary disc from which our planets emerged.