Cosmic symplectite found in meteorite Acfer 094 Credit: Ryan Ogliore, Laboratory for Space Sciences
Scientists confirmed their suspicions in 2011: There was a split within the local cosmos. The Genesis mission brought back samples of the solar wind to Earth. These samples proved that oxygen isotopes found in the sun are different from those on Earth, the Moon, and other planets and satellites within the solar system.
This is possible because material that would eventually coalesce into planets was exposed to a lot of ultraviolet light early in the history of the solar system. It is not clear where it came from. There are two theories: The ultraviolet light could have come from the sun's young sun or from a nearby star in its stellar nursery.
Researchers from Ryan Ogliore's lab, an assistant professor of physics at Washington University, St. Louis, have now determined the cause of the split. Most likely, it was light from a long-dead large star that made this impression on the rocky planets of the solar system. Lionel Vacher was a postdoctoral researcher in the Physics Department's Laboratory for Space Sciences.
The journal Geochimica et Cosmochimica Acta published their results.
Ogliore stated that "We knew we were born from stardust: That is, stars created in our galactic vicinity were part of the building blocks for the solar system."
"But this study also showed that starlight has a profound impact on our origins."
Tiny time capsule
Acfer 094, an asteroid discovered in Algeria as a meteorite, contained all of this profundity in a rock of only 85 grams. Although they are made from the same presolar material as planets, their formations have been affected by different natural processes. The rocky blocks that formed asteroids and planets were crushed and battered, vaporized, recombined, and then compressed and heated. Acfer 094 was able to survive for nearly 4.6 billion years largely unscathed.
Vacher stated, "This is one the most primitive meteorites we have," It was not heated in any significant way. It has porous areas and small grains that were formed around other stars. It serves as a reliable witness to how the solar system was formed."
Acfer 094 is also the sole meteorite to contain cosmic symplectite. This is a combination of iron-oxide, iron-sulfide and extremely heavy oxygen isotopes.
The sun has about 6% more lightest oxygen isotopes than the rest of our solar system. This can be explained by ultraviolet light shining onto the solar system's blocks and selectively breaking down carbon monoxide gas into its constituent parts. This process creates a large amount of heavier oxygen isotopes. This signature of heavy oxygen was not found in solar system materials until cosmic symplectite.
However, the only three isotopes available didn't suffice to answer the question about the origin of light. The same result could have been achieved by different ultraviolet spectra.
181-825 is one the bright proplyds proplanetary disks, and it lies close to Theta OrionisC, the Orion Nebula's brightest star. Credit: Credit: NASA/ESA, L. Ricci [ESO].
Vacher stated that Ryan was the one who came up with the idea for sulfur isotopes.
The four sulfur isotopes will leave different marks depending on how much ultraviolet light was irradiated by hydrogen sulfide in the protosolar system. The ultraviolet spectrum of a massive star and one that is young and sun-like have different spectra.
Cosmic symplectite was formed when the ices of an asteroid melted and were reacted with small amounts of iron-nickel metallic. Along with oxygen, cosmic symplectite also contains sulfur in iron-sulfide. Perhaps its sulfur witnessed the ancient astrophysical process that led to heavy oxygen isotopes.
Ogliore stated, "We created a model." What isotope anomalies could be created if I had a huge star? What about a young star that is sun-like? The experimental data will determine the precision of the model. Other scientists have performed amazing experiments to determine what happens when hydrogen sulfide has been exposed to ultraviolet light.
Another challenge was the measurement of sulfur and oxygen isotopes in cosmic symplectite at Acfer 094. These grains were tens of millimeters in diameter and a mixture of different minerals. This required two new techniques using in-situ secondary ion mass spectrometers, the NanoSIMS in physics (with Nan Liu, research assistant professor of physics), and the 7fGEO in the Department of Earth and Planetary Sciences.
The puzzle is complete
It was a great help to have friends in earth and planetary science, especially David Fike, professor in earth and planetary science and director of Environmental Studies in Arts & Sciences, as well as director at the International Center for Energy, Environment and Sustainability, and Clive Jones, research fellow in earth and planetary scientists.
Ogliore stated that "they are experts in high precision in-situ sulfur Iotope measurements biogeochemistry." We wouldn't have been able to distinguish between massive star and young sun scenarios without this collaboration.
The sulfur isotope measurements from cosmic symplectite matched ultraviolet radiation from a large star but were not consistent with the UV spectrum of the young sun. These results provide a unique insight into the astrophysical environment in which the sun was born 4.6 billion years ago. It is possible that nearby massive stars had a significant influence on the formation of the solar system. A nearby massive star would be brighter than the full Moon.
We can now look up and see that a similar story has played out in other parts of the galaxy.
Vacher stated that he saw nascent planet systems (called proplyds) in the Orion Nebula. These are being photoevaporated using ultraviolet light from nearby massive O- and B stars.
"If the proplyds get too close to these stars they can be torn apart and planets will never form. He said that we now know that our solar system was created at a distance close enough to these stars. "But fortunately, it is not too close. This work was supported by NASA grant NNX14AF22G and the McDonnell Center for Space Sciences at Washington University.
Learn more Ultraviolet sheds light on the origins of our solar system
More information: Lionel G. Vacher et Al, Cosmic symplectite documented irradiation from nearby massive stars in a parent molecular cloud of the solar system, Geochimica et Cosmochimica Acta (2021). Information for Journal: Geochimica et Cosmochimica Acta Lionel G. Vacher et. al., Cosmic symplectite reported that nearby massive stars radiated the solar system's parent molecular clouds, (2021). DOI: 10.1016/j.gca.2021.06.026