The origin of a dwarf planet lurking at the outer edge of the solar system that has become one of its strangest objects may have been revealed by NASA scientists.
Haumea it is about the size of another dwarf planet Pluto and is located in Kuiper belt, a collection of icy debris and cometary bodies outside Neptune’s orbit — the solar systemit is the most distant planet.
Haumea is notable for rotating faster than any other solar system object of similar size, completing one revolution on its axis — or a “day” — in just four hours.
This rapid rotation caused Haumea to develop a shape that resembles a deflated football rather than a sphere. However, its shape is not the only unusual thing about this dwarf planet.
A strange ice mystery
Haumea also has a surface mostly from a kind of water ice unlike most of the other Kuiper Belt bodies.
This water-ice surface is shared by some of Haumea’s siblings which also appear to share the same orbit as dwarf planet. This led scientists to conclude that Haumea and these icy bodies share the same origin and that they form the only “family” of related objects found in the Kuiper belt — the “Haumean family.”
Using computer simulations, including NASA scientists Goddard Space Flight Center in Greenbelt, Maryland, postdoctoral student Jessica Noviello investigated the question “How did something as strange as Haumea and her family come to be?”
Computer simulations are needed to accomplish this, as the dwarf planet is too far away to be accurately measured using an Earth-based telescope, and Haumea has yet to be visited by a space mission.
These simulations allowed the team to “tear apart” Haumea and then rebuild it from scratch. The aim of this was to understand the chemical and physical processes that formed the dwarf planet.
“To explain what happened at 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 throughout the solar system,” team member and University of Arizona at Tempe, professor of astrophysics. , Steve Desch told a statement. “There are a lot of weird, ‘gee whiz’ places in Haumea and trying to explain them all at once was a challenge.”
The model developed by the team started by inputting just three facts about Haumea. Its estimated size, its estimated mass, and its short four-hour “day”.
This provided a revised prediction of the dwarf planet’s size and mass, as well as its density. It also provided a prediction for the size and density of Haumea’s core.
Using this information, Noviello was able to determine how the dwarf planet’s mass is distributed and how that distribution has affected its rotation. From here, the researcher began simulating billions of years of evolution for Haumea, looking for the right set of characteristics that would result in the dwarf planet astronomers observe today.
“We wanted to really understand Haumea before we look back in time,” Noviello said.
The values of the Haumea family
The team hypothesized that the infant Haumea was about 3% larger than its current size, with this difference due to the creation of its Kuiper belt siblings.
Scientists also hypothesized that the young dwarf planet rotated at a different speed and that its mass was larger than it is today.
Changing the characteristics of Haumea in the models they developed allowed the team to run dozens of simulations to see how small changes such as increasing or decreasing the dwarf planet’s size changed its evolution.
Arriving at a model that delivered a simulation of Haumea exactly as astronomers observe it today, he told the team they had hit on the right early characteristics and current evolutionary path for the Kuiper belt dwarf planet.
Modeling by Noviello and her colleagues revealed that in its early years and during an epoch of the solar system characterized by chaotic conditions, Haumea collided with another body in a powerful impact.
This resulted in fragments of the young Haumea being detached, but these fragments did not become the objects of the Haumean family. This is because such a large impact would have knocked the pieces into far more scattered orbits than the Haumean bodies possessed.
Desch said the objects that make up the Haumean family would likely have actually formed later in the dwarf planet’s existence as its structure developed. In this later period of its evolution, dense, rocky material was sinking into the center of the dwarf planet while lighter-density ice rose to its surface.
“When you concentrate all the mass towards the axis, the moment of inertia is reduced, so Haumea ended up spinning even faster than it does today,” Desch said. This would result in rotational speeds fast enough to blow the ice that became the Haumean family off the surface.
This moment of inertia would have increased further, slowing the dwarf planet’s rotation rate as a result of radioactivity from the melting ice rocks of Haumea’s surface. This water soaked into the center of the dwarf planet caused the rocky material there to swell into a large but less dense core of clay.
The team’s research was published in the Planetary Science Journal on September 29.
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