The Pentagon Just Confirmed the First-Ever Interstellar Visitor to Earth
The United States Space Command (USSC) sent a letter on April 6 indicating that the meteor was certainly an interstellar object, proving its distant origins.
So far, government sensors on the lookout for fireballs hurtling toward Earth have recorded about 1,000 meteors and asteroids. Only one of them, however, can claim to have passed through our atmosphere from outside our Solar System.
This fireball that shot through our atmosphere above Papua New Guinea in 2014 was no ordinary space rock; it was an interstellar meteor, the first ever known to originate beyond our solar system and impact on Earth. The meteorite broke apart during its descent, perhaps sending interstellar debris into the South Pacific Ocean, as it rocketed at over 130,000 miles per hour.
5/ From the @AsteroidWatch tabletop exercise earlier this year, we learned that as long as the simulated asteroid was in the space domain, #USSPACECOM was the supported combatant command within the @DeptofDefense.
— U.S. Space Command (@US_SpaceCom) April 6, 2022
All previous rocky bodies that fell to Earth were assumed to have originated in our own Solar System before the USSC determined this meteor was a distant stranger. Many of them do come from a colony of millions of other boulders in the Asteroid Belt, which lies 111.5 million miles from Earth.
Two Harvard University academics were the first to investigate the remote sources of the 2014 meteor, publishing their findings on the preprint server arXiv in 2019. (meaning it was not peer-reviewed at the time). According to the researchers, the meteor’s extraordinarily high speed “implies a possible origin from the deep interior of a planetary system or a star in the thick disk of the Milky Way galaxy,” which will be resubmitted for publication in a peer-reviewed journal in light of the latest confirmation. The researchers searched through records of all fireballs identified by US government sensors since 1988.
Amir Siraj, one of the researchers, intends to find meteor debris on the ocean floor. Given the speed of the dissolving object—which was only a few feet wide—and the minute pieces that most likely resulted from the impact, it may be impossible. “We are currently investigating the possibility of embarking on an ocean expedition to recover the first interstellar meteorite. If found, the sample will be subjected to extensive study to determine its origin and the information it contains about its parent system, he writes in an email to Popular Mechanics.
“At first, I could hardly believe the discovery, since astronomers had been searching for an interstellar meteor since 1950 or earlier,” says Siraj, who is director of Interstellar Object Studies at Harvard’s Galileo Project, which aims to look for extraterrestrial technological artifacts.
The discovery was originally submitted to The Astrophysical Journal Letters by Siraj and his Harvard colleague Avi Loeb, who directs the Galileo Project. However, the assessment process dragged on for years due to missing data from the Center for Near Earth Object Studies (CNEOS) database, which identifies meteors and asteroids and analyzes their chances of impacting with Earth. Because the US Department of Defense operates some of the sensors that detect fireballs in order to monitor the skies for nuclear detonations, Siraj and Loeb were unable to validate the margin of error on the fireball’s velocity directly.
After moving through NASA, Los Alamos National Laboratory, and several bureaucratic departments, the sensor data finally ended up with Joel Mozer, chief scientist of Space Operations Command at the U.S. Space Force. The memo from Mozer confirmed that “the velocity estimate reported to NASA is sufficiently accurate to indicate an interstellar trajectory.”
Siraj learned the wonderful news through a NASA scientist’s tweet on April 6. He is currently reworking the paper in light of the government’s approval. “This confirmed impact of an interstellar object with the Earth’s atmosphere implies that similar objects are very common throughout space, which of course raises interesting questions about how they are ejected in such large quantities from their parent systems,” he says. Even if the rock’s remains are never discovered, data from the meteor’s fiery descent could reveal information about its composition and, possibly, origins.
Although the chances of a rock from another star system approaching Earth are remote, astronomers were aware of the two additional interstellar objects previous to this recently confirmed discovery. The quarter-mile-long asteroid Oumuamua was the first confirmed interstellar object discovered in the Solar System; the enormous rock was discovered in 2017 by Pan-STARRS, a wide-field astronomical imaging system in Hawaii. Gennady Borisov, an amateur astronomer, discovered Comet Borisov with his telescope in 2019. According to NASA, it is the first confirmed comet to approach our solar system from an unknown location outside the influence of our sun. However, neither of these distant visitors flew close to Earth.
Expanding our sensory capabilities with efforts like the new Vera C. Rubin Observatory’s planned ten-year survey is critical to “enhance our discovery rate of interstellar objects,” Siraj writes in an arXiv post in November 2021. Who can say? We may potentially discover extra-galactic objects, such as the particle discovered outside the Milky Way in 2007.