An article published in the “Planetary Science Journal” reports the results of simulations that reproduce the possible history of the dwarf planet Haumea that led to its peculiar oval shape. A team of researchers used the geophysical and geochemical data available on Haumea and the asteroids that form a family with this dwarf planet to understand what processes led to their formation and evolution. The simulations lead to a reconstruction of the process that resulted in Haumea’s remarkable fast spin, which in turn led to its present shape.
Discovered in 2004, Haumea was classified as a dwarf planet in 2008. Its distance from the Sun is currently about 50 times the Earth’s and has a year that is about 284 Earth years. The image (©Pablo Carlos Budassi) shows an artistic representation of Haumea with its moons Hiʻiaka and Namaka, which are actually much farther away from it, and the ring whose discovery was announced in 2017.
Haumea’s observations conducted after its discovery quickly led to noting fluctuations in its brightness over a period of 3.9 hours and only this dwarf planet’s spin can explain this. It’s a very fast spin, significantly faster than any planet or dwarf planet in the solar system. It’s such a speed that it leads to the elongated shape we know today.
A hypothesis to explain the dwarf planet Haumea’s fast spin is a collision at the beginning of its history that also led to the formation of the asteroids existing in its own orbit and considered part of its family. The problem is that the various scenarios linked to a collision would have led to very different consequences for Haumea and that makes it difficult to understand what really happened. This new study proposes a different explanation.
The data available on the dwarf planet Haumea is limited due to its considerable distance but the researchers collected it and used it to estimate the unavailable data. An important parameter for the simulations is the amount of frozen water present on Haumea, which almost completely covers its surface.
According to the researchers, around the time of Haumea’s formation, denser rocky materials started concentrating towards its center while the ice rose to the surface. Simulations suggest that Haumea’s core formed just over 4.4 billion years ago. The processes of the materials’ shift influenced the new dwarf planet’s moment of inertia causing it to spin faster. At one point, that spin was so fast that it ejected parts of the surface, which went on to form the asteroids of its family.
The simulations also suggest that the amount of radioactive materials present in Haumea’s core after its formation generated enough heat to create an underground ocean. The liquid water soaked into the rocks forming a considerable clay layer with a density lower than the rocky one. The result was an increase in the moment of inertia and a consequent spin slowdown, which reached the current speed. Over time, the radioactive materials decayed and the water froze.
This study offers an explanation for all the peculiarities of Haumea and its family. There could still be discussions, also because it’s difficult to collect other reliable data on this dwarf planet and its asteroid family due to their distance. It would take a spacecraft many years to reach Haumea for even just a flyby at very high speed. Despite this, scientists are slowly reconstructing the history of one of the strangest objects in the solar system.
