Diary of an Interstellar Voyage, Report 22 (June 22, 2023)
Following our daily team meeting today on the upper floor of Silver Star, we established a procedure for processing the material retrieved from our sleds. The latest retrievals include Run 11 with the sluicing device, which selected high-density particles independent of their magnetic properties. The latest Runs 12 & 13 brought back a new collection of corroded iron shards and loads of black powder (magnetite) — where we search for sub-millimeter spherules from the first recognized interstellar meteor, IM1.
I established a counter for IM1’s spherules, which currently stands at 11, out of which 9 are from Run 8, and ones from Runs 9 & 12. The counter lies as a motivation banner above the workspace of Ryan Weed, who mastered the art of isolating these metallic pearls using tweezers with the help of microscope imaging.
If an equal amount of total mass was deposited per logarithmic spherule mass, we will need to count about a thousand spherules of 0.3-millimeter diameter before we should statistically expect to encounter the first 3-millimeter spherule.
It is difficult to identify visually or separate with tweezers spherules smaller than 0.25-millimeter and so we are using a filter with this mesh size. Moreover, smaller spherules are swamped by the vast abundance of tiny particles in volcanic ash. There is therefore a sweet spot at around a size of 0.25 millimeter for finding metallic pearls that are visible in our microscope images, easy to handle with our tweezers, and are not as rare as their bigger counterparts.
It was a matter of pure luck that the meter-sized sled could find 9 spherules bigger than a quarter of a millimeter across the 10-kilometer length of Run 8. If the meteor had less than half its size — equivalent to a mass reduction by at least a factor of 8, we would have been blind to the population of spherules because of their statistical rarity.
We were also lucky that the meteor exploded above the ocean, where the sample of tiny spherules was preserved without resurfacing or sedimentation on top of it. If the fireball would have occurred above the Sahara desert, the spherules would have been buried in sand by now as a result of dusty winds.
My Harvard colleague, Xingang Chen, wrote to me that the Chinese counterpart of the idiom “finding a needle in a haystack” is “finding a needle in an ocean”, meaning that something is close to impossible. This indeed fits the mission of our Galileo Project expedition to find tiny spherules from the first recognized interstellar meteor, IM1.
The microscope images of Run 5 indicated smaller spherules than those found in Run 8, but these small spherules are impossible to isolate with our tweezers. Interestingly, line 8 continued farther along the meteor path than line 5 and so its crop included bigger spherules which suffered less friction with air thanks to their smaller area-per-mass ratio.
Given that the meter-scale width of the sled is about a thousand times shorter than the width of the expected IM1 strewn field, I estimated that IM1 must have produced about ten thousand spherules larger than a quarter of a millimeter. This number agrees with the value expected from a detailed theoretical model that I published a year ago with the students Amory Tillinghast-Raby and Amir Siraj.
Altogether, the remarkable findings of IM1 spherules by our team opens a new frontier of discovery for the material composition of interstellar meteors. This frontier could shed new light on the evolution of exoplanetary systems as well on the possible existence of technological space objects from other civilizations. The collaborative spirit and comradery established through this successful mission laid a solid foundation for follow-up expeditions by the same team for years to come.
I was asked by a prominent podcaster yesterday whether I have questions for a famous science popularizer that he will host, and I replied that as of now I am busy finding answers to big cosmic questions on ocean floors. This demanding activity leaves me little time for small talk.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He chairs the advisory board for the Breakthrough Starshot project, and is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, is scheduled for publication in August 2023.
