In a new study published in the Proceedings of the National Academy of Sciences (PNAS), scientists were able to figure out how long ago a supernova star exploded and how much time our solar system spent traveling through its stellar guts. Not only was the length of time our solar system spent in the star’s remains surprising, it also coincides with an extinction event in Earth’s oceans, as well as a period of global cooling. This supernova was so close to our planet that, depending on where it went off, our evolutionary ancestors might have seen it as a bright light in the sky. Scientists used a different type of ocean sediment from the Pacific Ocean that grows at a rate of 10-20 meters every million years. They were searching for atoms of a radioactive isotope of iron called iron-60. Iron-60 is not produced on Earth, and can only be produced in these massive, exploding stars. In fact, this supernova debris is the first place in the history of our species that we’ve even seen it. So what was it that preserved this 2.6 million-year-old radioactive isotope?
According to Shawn Bishop, a physicist at the Technical University of Munich in Germany and coauthor of the study, it’s all thanks to a family of bacteria that lives in the ocean sediments. These bacteria grow dozens of tiny crystals of magnetite, composed of iron and oxygen, in their cells. These crystals, Bishop said, are actually tiny bar magnets. They get their iron from nanosized rust particles falling into the surface of the ocean from our atmosphere. Using a technique that allowed them to count the atoms of iron-60 in the crystals, the scientists were able to figure out that the supernova went off about 2.6 million years ago, and our solar system twirled through its guts for 800,000 years.

Source: Businessinsider.com