Extraterrestrial Stone Could Be First Evidence Found On Earth Of A Supernova Explosion: Study
The stone named Hypatia discovered from the Great Sand Sea desert in Egypt could be the first tangible evidence found on Earth of a supernova type Ia explosion, which are rare, and extremely energetic
New Delhi: The stone named Hypatia discovered from the Great Sand Sea desert in Egypt could be the first tangible evidence found on Earth of a supernova type Ia explosion, new chemistry "forensics" indicate. Type Ia supernovae are rare supernovae which are some of the most energetic events in the universe.
These supernovae occur in binary systems, in which two stars orbit one another, one of which is a white dwarf, and the other can be anything from a giant star to an even smaller white dwarf. Type Ia supernovae, also known as thermonuclear supernovae, do not take place when the core of a massive star collapses, and are the brightest of all supernovae. They are characterised by a silicon absorption feature in their maximum light spectra. The supernovae are thought to be the result of the explosion of a carbon-oxygen white dwarf in a binary system.
The study, describing the findings on Hypatia, and led by researchers from University of Johannesburg, were recently published in the journal Icarus.
Researchers Eliminated “Cosmic Suspects” For Hypatia’s Origin
Jan Kramers and Georgy Belyanin from the University of Johannesburg, who were involved in the study, have been uncovering a series of highly unusual chemistry clues in a small fragment of the Hypatia stone, since 2013. In the new study, the researchers have eliminated "cosmic suspects" for the origin of the stone in a painstaking process, and have pieced together a timeline stretching back to the early stages of formation of Earth, the Sun, and other planets in the solar system.
Cosmic Timeline Of Hypatia’s Origin
The scientists' hypothesis about Hypatia's origin starts with a star, and states that a red giant star collapsed onto a white dwarf star. The collapse would have happened inside a gigantic dust cloud, called a nebula, according to the hypothesis.
The white dwarf was present in a binary system with a second star, and eventually "ate" the other star. There came a point at which the "hungry" white dwarf exploded as a supernova type Ia inside the dust cloud.
The gas atoms which remained of the supernova Ia after cooling started sticking to the particles of the dust cloud. In a statement released by University of Johannesburg, Kramers said that the researchers have 'caught' a supernova Ia explosion 'in the act', because the gas atoms from the explosion were caught in the surrounding dust cloud, which eventually formed Hypatia's parent body.
Also, a huge "bubble" of this supernova dust-and-gas-atoms mix never interacted with other dust clouds, the statement said.
After millions of years passed, the "bubble" slowly became a solid, in a "cosmic dust bunny" kind of way, and Hypatia's "parent body" became a solid rock some time in the early stages of the formation of the solar system.
The process probably happened in a cold, uneventful outer part of the solar system, in the Oort cloud or in the Kuiper Belt, and at some point, Hypatia's parent rock started hurtling towards Earth. The heat of entry into Earth's atmosphere, combined with the pressure of impact in the Great Sand Sea in south-western Egypt, created micro-diamonds and shattered the parent rock, as a result of which the Hypatia stone, which is one of the many fragments of the original impactor, was obtained.
Kramers said that if the hypothesis is correct, the Hypatia stone would be the first tangible evidence on Earth of a supernova type Ia explosion, and shows that an individual anomalous 'parcel' of dust from outer space could actually be incorporated in the solar nebula our solar system was formed from, without being fully mixed in.
He explained that this goes against the conventional view that dust which our solar system was formed from was thoroughly mixed.
Proton Beam Used To Analyse Hypatia
The researchers used several techniques to analyse the stones, and to piece together the timeline of how Hypatia may have formed. A 2013 study of the argon isotopes showed the rock was not formed on Earth, and had to be extraterrestrial. According to a 2015 study of noble gases in the fragment, the stone may not be from any known type of meteorite or comet.
The University of Johannesburg team published various analyses in 2018, which included the discovery of a mineral, nickel phosphide, that was not previously found in any object in our solar system.
Hypatia, at that stage, was proving difficult to analyse further. In order to visualise some trace metals in detail, Kramers and Belyanin needed a more powerful instrument that would not destroy the tiny sample.
Belyanin had created a dataset a few years before, which Kramers started analysing. Belyanin, in 2015, had done a series of analyses on a proton beam at the iThemba Labs in Somerset West.
Kramers said that rather than exploring all the incredible anomalies Hypatia presents, the scientists wanted to explore if there is an underlying unity, and wanted to see if there is some kind of consistent chemical pattern in the stone.
Belyanin selected 17 targets on the tiny sample for analysis, in a way such that they were well away from the earthly minerals that had formed in the cracks of the original rock after its impact in the desert.
15 Different Elements In Hypatia Identified
Belyanin said that the researchers identified 15 different elements in Hypatia with much greater precision and accuracy, with the proton microprobe. This gave the scientists the 'ingredients' they needed, so that Kramers could start the next process of analysing all the data.
Kramers added that high iron, high sulphur, high phosphorus, high copper, and high vanadium were conspicuous and anomalous.
Did Hypatia Originate From A Meteor Or Asteroid?
He said that they found a consistent pattern of trace element abundances that is completely different from anything in the solar system, primitive or evolved. Objects in the asteroid belt and meteors do not match this either; hence, the team looked outside the solar system next.
Did Hypatia Come From Solar System Arm Of Milky Way?
According to the study, Kramers compared the Hypatia element concentration pattern with what one would expect to see in the dust between stars in the solar system arm of the Milky Way galaxy. He said that the researchers looked to see if the pattern they got from average interstellar dust in the arm of the Milky Way galaxy fits what they see in Hypatia. Again, there was no similarity at all, he said.
What Were The Four “Suspects” Ruled Out By Proton Beam?
The proton beam data had ruled out four "suspects" of where Hypatia could have formed. According to the study, Hypatia did not form on Earth, was not part of any known type of comet or meteorite, did not form from average inner solar system dust, and not from average interstellar dust either.
Could A Red Giant Star Explain Hypatia’s Element Concentration?
The next simplest possible explanation for the element concentration pattern in Hypatia was a red giant star, which is commonly found in the universe. However, the proton beam data ruled out mass outflow from a red giant star, because Hypatia had too much iron, too little silicon, and too low concentrations of heavy elements heavier than iron, the study said.
Did A Supernova Type II Explosion Form Hypatia?
The next suspect was a supernova type II, which cooks up a lot of iron. These supernovae are also a relatively common type of supernova.
However, the proton beam data for Hypatia ruled out the promising suspect with "chemistry forensics". According to the study, a supernova type II was highly unique as the source of strange minerals like nickel phosphide in the pebble. Also, there was too much iron in Hypatia compared to silicon and calcium.
Supernova Type Ia Explosion Gave Rise To Hypatia?
Therefore, it was time to closely examine the predicted chemistry of one of the most dramatic explosions in the universe.
Supernova type Ia, which is a rarer kind of supernova, also makes a lot of iron. They happen only once or twice per galaxy per century. However, supernova type Ia manufactures most of the iron in the universe, and most of the steel on Earth was once the element iron created by these supernovae.
Some Ia supernovae leave very distinctive 'forensic chemistry' clues behind because of the way Ia supernovae are set up.
A red giant star at the end of its life collapses into a very dense white dwarf, which is usually incredibly stable for very long periods and most unlikely to explode. However, there are exceptions to this, the study said.
This is because a white dwarf could start "pulling" matter off another star in a binary system, because of which the white dwarf can be described as eating up its companion star. The white dwarf star gets so heavy, hot, and unstable, that it explodes in a supernova Ia.
Accepted scientific theoretical models predict that the nuclear fusion during the supernova Ia explosion should create highly unusual element concentration patterns.
What Happens To A White Dwarf Star In A Supernova Ia?
According to the study, the white dwarf star that explodes in a supernova Ia is not just blown to bits, but literally blown to atoms. As a result, the supernova Ia matter is delivered into space as gas atoms.
The team, in an extensive literature search of star data and model results, could not identify any similar or better chemical fit for the Hypatia stone than a specific set of supernova Ia models, the study said.
Kramers said that all supernova Ia data and theoretical models show much higher proportions of iron compared to silicon and calcium than supernova II models. He added that in this respect, the proton beam laboratory data on Hypatia fit to supernova Ia data and models.
Which Elements Conform To Predicted Ranges Of Proportions Relative To Iron?
According to the study, eight of the 15 elements analysed conform to the predicted ranges of proportions relative to iron. These elements are silicon, sulphur, calcium, titanium, vanadium, chromium, manganese, iron, and nickel.
According to the study, not all 15 of the analysed elements in Hypatia fit the predictions. In six of the 15 elements, proportions were between 10 and 100 times higher than the ranges predicted by theoretical models for supernova type Ia. These elements were aluminium, phosphorus, potassium, chlorine, copper, and zinc.
Where Did Hypatia Inherit The Six Elements From?
Kramers said that since a white dwarf star is formed from a dying red giant, Hypatia could have inherited these element proportions for the six elements from a red giant star. The phenomenon has been observed in white dwarf stars in other research, he explained.
If the hypothesis is correct, the Hypatia stone would be the first tangible evidence on Earth of a supernova type Ia explosion, one of the most energetic events in the universe, the study said.
The Hypatia stone would be a clue of a cosmic story started during the early formation of the solar system, only to be found many years later in a remote desert strewn with other pebbles, the researchers noted in the study.
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