In spring 2023, a Galileo Project team plans to board a boat and use a sled with a magnet to scoop the ocean floor near Papua New Guinea. This “fishing expedition” aims to collect fragments from the first interstellar meteor (IM1), reported in the CNEOS fireball catalog on January 8, 2014. The interstellar origin was first inferred in a paper that I published this month with my student Amir Siraj in The Astrophysical Journal. Our discovery was confirmed at a confidence level of 99.999% in a letter from the US Space Command.
The first interstellar meteor was observed to move at a speed of 45 kilometers per second when it exploded at an altitude of 18.7 kilometers above the ocean surface. The ram-pressure of the air at its breakup altitude was a few times above the yield strength of iron. This interstellar object was tougher than all other 272 meteors in the CNEOS catalog. For reference, it was twenty times tougher than stony meteorites which make up 95% of all Solar system meteors. Was it a rare iron meteorite or a spacecraft made of stainless steel? The best way to find out is by collecting meteor fragments and analyzing their composition.
The bright light detected from the fireball implies that the explosion released a few percent of the energy associated with the Hiroshima atomic bomb during World War II. The meteor size is inferred to be half a meter based on its speed and kinetic energy. The huge energy release melted the object into tiny droplets. The smallest fragments, less than the size of the head of a pin, were stopped quickly by friction on air owing to their large surface area per unit mass. They fell straight down from the explosion site as hot rain, raised steam from the ocean surface, and sank down to the ocean floor. Larger fragments continued farther along the original path of the meteor. As a result, we expect to find a strip of fragments on the ocean floor, oriented in projection along the original path of the meteor, with the smallest fragments marking the beginning of the strip straight below the explosion site and larger fragments farther along.
How many fragments should we expect of different sizes? This was the focus of a new paper that I wrote with a summer intern, Amory Tillinghast-Raby, and Amir Siraj. Our forecast depends on composition. For an iron meteorite, we predict about a thousand fragments bigger than a millimeter, whereas for a stainless-steel composition we expect larger sizes, with tens of fragments bigger than a centimeter. The size distribution of the fragments can be used to infer their material strength even before we analyze their composition in the laboratory.
The unusual material strength is not a rare finding within the interstellar meteor population. Recently, I wrote another paper with Amir that identified a second interstellar meteor (IM2) which was reported in the CNEOS catalog on March 9, 2017 and was also extremely tough. The chance of drawing these both interstellar meteors out of the material strength distribution of Solar system meteors is smaller than 0.01%. A follow-up expedition will aim to collect the fragments of the second interstellar meteor near Portugal.
In case we recover a large technological relic, I promised the curator of the Museum of Modern Art, Paula Antonelli, that I will bring it for display in New York. For humanity this piece would represent modernity, even though for its senders it represents ancient history.
This will be the first time that humans retrieved a large piece of material from outside the Solar system. If the piece has some buttons on it, we can only hope that they remained functional. An extraterrestrial device would be of much interest not only to art collectors but also to entrepreneurs from Silicon Valley.
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.