A space rock discovered more than two decades ago could be the first physical evidence of a rare type of powerful stellar explosion called a Type Ia supernova, according to a new study.
In 1996, a researcher working in the Egyptian desert found a small rock that scientists later determined was most likely of extraterrestrial origin, as it contained mysterious mineral compounds not found anywhere else on Earth. In a new study, scientists at the University of Johannesburg in South Africa say they have found that this space rock, named the Hypatia Rock after the ancient Greek philosopher and astronomer, may be the first physical evidence of a Type Ia supernova, one of the most energetic phenomena in the universe.
The team conducted years of research, including studies in 2013, 2015 and 2018, which showed that the stone did not originate on Earth, from a meteorite or comet, or from any other part of the solar system, respectively.
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(Image credit: Romano Serra)
In their new analysis of the Hypatia stone, scientists used the proton beam, a high-energy particle accelerator that identified 15 elements in more detail than ever before. Using these clues, the team began to reconstruct the locations from which the stone might have originated using a process of elimination.
For example, the amount of silicon in Hypatia’s rock was extremely low—less than 1% of what would be expected for an object that formed in our solar system. Likewise, the levels of chromium, manganese, iron, sulfur, copper, and vanadium were not typical of the solar system’s inner material.
“We found a consistent trace element abundance pattern that is completely different from anything in the solar system, whether primitive or evolved,” study lead author Jan Kramers, a geochemist at the University of Johannesburg, said in a statement. “Objects in the asteroid belt and meteors don’t fit that either. So then we looked beyond the solar system.”
They kept changing their parameters according to various possible sources, including interstellar dust lanes in the Milky Way, a red giant star, and even a Type II supernova, which occurs when a massive star runs out of fuel, collapses, and then explodes. However, the composition of the Hypatia stone ruled out each of these possibilities.
(Image courtesy of NASA’s Goddard Space Flight Center Conceptual Imaging Lab)
So the scientists investigated whether the source could be a Type Ia supernova, a super-powerful explosion that occurs when a dense, dim remnant of a star called a white dwarf in a binary system explodes with such force that the white dwarf breaks into atoms. Once these atoms are solidified with dust from the white dwarf nebula, the resulting rocky material would theoretically have a very specific chemical characteristic, the scientists say.
It turned out that the chemical characteristics of the Hypatia stone are very similar to the chemical characteristics of the supernova, which scientists have assumed for a type Ia supernova. However, they did not match 100%.
“In six of the 15 elements, the proportions were 10 to 100 times higher than the ranges predicted by theoretical models for type Ia supernovae,” the scientists said in a statement. “These are the elements aluminium, phosphorus, chlorine, potassium, copper and zinc.”
The researchers hope to explain these abnormal levels with more analysis. At the same time, they are enthusiastic about the prospect of potential supernova evidence and what they can say about the origin of the solar system.
“Perhaps just as importantly, this shows that a single anomalous ‘send’ of dust from space can be incorporated into the solar nebula from which our solar system was formed without completely mixing with it,” Kramers said. “This goes against the conventional wisdom that the dust from which our solar system formed was thoroughly mixed.”
The team’s research is published in the August 2022 issue of Icarus.
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