A Specific Kind of Stellar Outburst produces the Stardust Grains

A Specific Kind of Stellar Outburst produces the Stardust Grains

A Specific Kind of Stellar Outburst produces the Stardust Grains
Image Credits: ASU Now

According to a new model of Nova Eruptions, stardust grains were produced by a particular type of stellar outburst.

A couple of researchers from the Arizona State University (ASU) studied the microscopic stardust grains in order to unravel the mystery of Silicon Carbide stardust (found in aging stars and meteorites). Both, Summer Starrfield (an Astrophysicist) and Maitrayee Bose (a Cosmochemist) belong to the School of Earth and Space Exploration at ASU. They were successful in pinpointing the kind of stellar outburst that gave birth to the stardust grains. The study explained that repeated cataclysmic eruptions by certain types of white dwarf stars created these Silicon Carbide grains, which were then embedded in primitive meteorites. Referring to that, Bose said,

“Silicon carbide is one of the most resistant bits found in meteorites. Unlike other elements, these stardust grains have survived unchanged from before the solar system was born.”

Violent Birth of Stardust Grains

Nova eruptions occur in pairs of stars where a cool giant star feeds gas onto a hot white dwarf star. The outer atmosphere of the cooler star continues to pass interstellar gas to the white dwarf star until it produces a massive thermonuclear eruption. This violent reaction gives birth to a new star, which is referred to as a ‘Nova’. Despite the fact that it is an extremely powerful explosion, neither the white dwarf nor its companion is destroyed and novae keep on erupting over and over. Consequently, more and more interstellar gas and stardust grains are added to their surroundings. Both of these commodities eventually merge with each other to become the ingredients of new star systems.

One of these interstellar clouds resulted in the formation of our Sun and Solar System, about 4.6 billion years ago. Almost all the stardust grains (apart from some tiny specks of Silicon Carbide) from earlier stellar eruptions were consumed during the process. The presolar grains that were left behind can be identified in primitive solar system materials like Chondritic Meteorites. Bose described their experience of discovering the stardust in the following words:

“The key that unlocked this for us was the isotopic composition of the stardust grains. Isotopic analysis lets us trace the raw materials that came together to form the solar system. Each silicon carbide grain carries a signature of the isotopic composition of its parent star. This provides a probe of that star’s nucleosynthesis — how it made elements.”

Bose was able to group all the grains of stardust into three main categories, except 30 grains that couldn’t be traced back to any specific stellar origin. Therefore, it was believed that they originated in nova explosions but no physical evidence was there to support this idea.

Latest Model for Tracing Stardust Grains

Starrfield studies various types of stellar explosions ranging from novae to supernovae and from X-ray bursts to recurrent novae. He uses computer simulations and calculations for compiling his theoretical results. He was trying to develop a computer model that could explain the ejected materials of nova (discovered in 2015) when he attended a colloquium talk of Bose. That was the time when he decided to dig deeper into the details of Nova eruptions and presolar stardust grains. He mentioned that by saying,

“I would not have pursued this if I hadn’t heard Maitrayee’s talk and then had our follow-up discussion. After talking with her, I discovered our initial way of solving the problem was not agreeing with either the astronomical observations or her results. So I had to figure out a way to get around this.”

He designed a completely new method of doing the model calculation by using multidimensional studies of classical nova eruptions. He was previously working on the Oxygen-Neon class of nova for 20 years and decided to shift to the Carbon-Oxygen class in an attempt to find some important results. His calculations made predictions for 35 isotopes that would be created due to Carbon-Oxygen nova eruptions.


The researching team observed that getting the right proportion of accreted and the white dwarf core material is absolutely necessary for the simulations to work. In order to draw a conclusion, both the researchers compared the predictions with the published compositions of stardust grains. The results they got were disappointing yet important as they found that only 5 of the 30 grains could have come from novae. Bose mentioned that it is a positive result because they will now have to search for the new stellar source(s) in order to explain the remaining stardust grains. Talking about a larger perspective, she said,

“We have also found that astronomical observations, computer simulations, and high-precision laboratory measurements of stardust grains are all needed if we want to understand how stars evolve. And this is exactly the kind of interdisciplinary science that the school excels at.”

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