NASA scientists may have revealed the origin of the dwarf planet that lurks at the outer edge of the Solar System and has become one of its strangest objects. Haumea is about the same size as the dwarf planet Pluto and is located in the Kuiper Belt, a cluster of icy debris and cometary bodies orbiting Neptune, the outermost planet of the Solar System, reports Space.com.
Haumea is notable for rotating faster than any other solar system object of its size, completing a rotation around its axis — or “day” — in just four hours.
This rapid rotation caused Haumea to take on a shape more like a deflated soccer ball than a sphere. However, the shape is not the only feature of this dwarf planet. Haumea also has a surface that is primarily composed of a type of water ice, unlike most other bodies in the Kuiper belt.
This water-ice surface is shared by some of Haumea’s “siblings,” which also appear to be orbiting the dwarf planet. This led scientists to the conclusion that Haumea and these icy bodies have the same origin and that they form a single “family” of related objects found in the Kuiper belt – the “Haumean family”.
Using computer simulations, NASA scientists investigated the question “How did something as weird as Haumea and its family come to be?”
Computer simulations are necessary to achieve this goal because the dwarf planet is too far away to be accurately measured by a ground-based telescope, and Haumea has not yet been visited by a space mission.
These simulations allowed the team to “take apart” Haumea and then “rebuild” it from scratch. The goal of this was to understand the chemical and physical processes that formed the dwarf planet.
“To explain what happened to Haumea forces us to put time limits on all these things that happened when the solar system was forming, so it starts to connect everything across the solar system,” said in a statement a team member and professor of astrophysics at Arizona State University in Tempe Steve Desch. “There are a lot of odd, ‘gee whiz’ parts to Haumea, and trying to explain them all at once has been a challenge.”
The team’s model began by entering just three pieces of information about Haumea: its estimated size, its estimated mass, and its short four-hour “day.” This made it possible to obtain a refined forecast of the size and mass of the dwarf planet, as well as its density. It also became possible to predict the size and density of Haumea’s core.
Using this information, scientists were able to determine how the mass of the dwarf planet was distributed and how this distribution affected its rotation. Next, the researchers began modeling Haumea’s billions of years of evolution in search of the right set of characteristics that would have led to the dwarf planet becoming the way astronomers observe it today.
The team hypothesized that newborn Haumea was about 3% larger than its current size, a difference that explains the creation of its Kuiper Belt siblings.
Scientists also suggested that the young dwarf planet rotated at a different speed and that its volume was larger than today.
Varying the characteristics of Haumea in the models they developed allowed the team to run dozens of simulations, observing how small changes, such as increasing or decreasing the dwarf planet’s size, changed its evolution.
After obtaining a model that reproduced Haumea just as astronomers observe it today, the team realized that they had found the correct early features and the current evolutionary path of the Kuiper Belt dwarf planet.
The simulations showed that Haumea collided with another body in a powerful collision during the first years of its existence and during the era of the solar system, which was characterized by chaotic conditions.
This caused pieces to break off from the young Haumea, but the fragments did not become objects of its family. This is because such a large impact would have knocked the pieces into far more scattered orbits than that possessed by the Haumean family bodies.
The objects that make up the Haumean family would probably actually have formed later in the dwarf planet’s existence as its structure evolved. During this late period of its evolution, dense rocky material sank to the center of the dwarf planet, while lighter ice rose to its surface.
This moment of inertia would be further increased by reducing the dwarf planet’s rotation speed as a result of radioactivity from Haumea rocks melting on the ice surface.This water soaked to the center of the dwarf planet caused rocky material there to swell to a large but less dense clay core.