In this study, published online last month in Earth and Planetary Science Letters, authors Haolan Tang and Nicolas Dauphas found the radioactive isotope iron 60 — the telltale sign of an exploding star—low in abundance and well mixed in solar system material. As cosmochemists, they look for remnants of stellar explosions in meteorites to help determine the conditions under which the solar system formed.
Some remnants are radioactive isotopes: unstable, energetic atoms that decay over time. Scientists in the past decade have found high amounts of the radioactive isotope iron 60 in early solar system materials. “If you have iron 60 in high abundance in the solar system, that’s a ‘smoking gun’—evidence for the presence of a supernova,” said Dauphas, professor in geophysical sciences.
Iron 60 can only originate from a supernova, so scientists have tried to explain this apparent abundance by suggesting that a supernova occurred nearby, spreading the isotope through the explosion.
But Tang and Dauphas’ results were different from previous work: They discovered that levels of iron 60 were uniform and low in early solar system material. They arrived at these conclusions by testing meteorite samples. To measure iron 60’s abundance, they looked at the same materials that previous researchers had worked on, but used a different, more precise approach that yielded evidence of very low iron 60.
Previous methods kept the meteorite samples intact and did not remove impurities completely, which may have led to greater errors in measurement. Tang and Dauphas’ approach, however, required that they “digest” their meteorite samples into solution before measurement, which allowed them to thoroughly remove the impurities.
This process ultimately produced results with much smaller errors. “Haolan has dedicated five years of very hard work to reach these conclusions, so we did not make those claims lightly. We’ve been extremely careful to reach a point where we’re ready to go public on those measurements,” Dauphas said.
To address whether iron 60 was widely distributed, Tang and Dauphas looked at another isotope of iron, iron 58. Supernovae produce both isotopes by the same processes, so they were able to trace the distribution of iron 60 by measuring the distribution of iron 58.
“The two isotopes act like inseparable twins: Once we knew where iron 58 was, we knew iron 60 couldn’t be very far away,” Dauphas explained.
They found little variation of iron 58 in their measurements of various meteorite samples, which confirmed their conclusion that iron 60 was uniformly distributed. To account for their unprecedented findings, Tang and Dauphas suggest that the low levels of iron 60 probably came from the long-term accumulation of iron 60 in the interstellar medium from the ashes of countless stars past, instead of a nearby cataclysmic event like a supernova.
If this is true, Dauphas said, there is then “no need to invoke any nearby star to make iron 60.” However, it is more difficult to account for the high abundance of aluminum 26, which implies the presence of a nearby star.
Instead of explaining this abundance by supernova, Tang and Dauphas propose that a massive star (perhaps more than 20 times the mass of the sun) sheds its gaseous outer layers through winds, spreading aluminum 26 and contaminating the material that would eventually form the solar system, while iron 60 remained locked inside the massive star’s interior. If the solar system formed from this material, this alternate scenario would account for the abundances of both isotopes.
“In the future, this study must be considered when people build their story about solar system origin and formation,” Tang said. — Chelsea Leu
Citation: “Abundance distribution, and origin of 60Fe in the solar protoplanetary disk,” by Haolan Tang and Nicolas Dauphas, Earth and Planetary Science Letters, December 2012.
Funding: National Aeronautics and Space Administration, National Science Foundation, and the Packard Foundation.
Steve Koppes | Newswise
Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science
NASA's fermi finds possible dark matter ties in andromeda galaxy
22.02.2017 | NASA/Goddard Space Flight Center
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
22.02.2017 | Power and Electrical Engineering
22.02.2017 | Life Sciences
22.02.2017 | Physics and Astronomy