December 17, 2012
Evidence Found That Exploding Star Gave Birth To Solar System
Lee Rannals for redOrbit.com — Your Universe Online
University of Chicago researchers wrote in the journal Earth and Planetary Science Letters that they found the radioactive isotope iron 60 low in abundance, and well mixed in solar system material, leading to the notion that the force of an exploding star prompted the formation of the Solar System.
Scientists look for remnants of stellar explosions in meteorites to help determine the conditions under which the solar system formed. Some of the remnants that cosmochemists find are radioactive isotopes, which are unstable, energetic atoms that decay over time.
In the past, scientists have found high amounts of the radioactive isotope iron 60 in early solar system materials.
Iron 60 can originate from a supernova, so scientists have tried explaining this abundance by suggesting that a supernova occurred nearby, spreading the isotope through the explosion.
The scientists' results were different from previous work, discovering that levels of iron 60 were uniform and low in early solar system materials. The team found this by testing meteorite samples.
The researchers looked at the same materials that previous studies worked on, but used a different approach that yielded evidence of very low iron 60.
Past methods kept the meteorite samples intact and did not remove impurities completely. The new approach required that they "digest" the meteorite samples into solutions before measurement.
“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.
They looked at another isotope of iron (iron 58) to address whether this one was widely distributed. 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 did not find much of a variation of iron 58 in their measurements of various meteorite samples. In order to account for their unprecedented findings, the team suggest that the low levels of iron 60 probably come from the long-term accumulation of iron 60 in the interstellar medium from the ashes of countless stars past.
Dauphas said there is "no need to invoke any nearby star to make iron 60." They said it was more difficult to account for the high abundance of aluminum 26, which implies the presence of a nearby star.
The team believes that a massive star sheds its gaseous outer layers through winds, spreading aluminum 26 and contaminating the material that would eventually form the solar system.
“In the future, this study must be considered when people build their story about solar system origin and formation,” said Haolan Tang, a coauthor of the paper.