A small meteor that whizzed over the skies of Papua New Guinea in 2014 was a visitor from another star system, making it the first known interstellar meteor – and our first known interstellar visitor – according to newly declassified US government data.
In 2017, we had our first-ever confirmed interstellar visitor. The object, ‘Oumuamua, was spotted traveling through our Solar System possibly from another star about 200 light-years away. ‘Oumuamua (pronounced: oh-MOO-a-MOO-a) was so novel that questions abound: was it a comet, asteroid, or alien spaceship?
Two years later, two scientists claimed they found not just an earlier interstellar visitor, but one that crashed into Earth in 2014. A paper was written but couldn’t be verified because some important data was missing – data that was classified according to the US government.
Now, the US Space Command has confirmed in a memo released last week that “a previously-detected interstellar object was indeed an interstellar object”.
In the year or two after ‘Oumuamua was discovered, scientists debated the object’s origins. While some scientists argued whether it was a comet or an asteroid, others put forward more “out there” hypotheses ranging from it being a chunk of dark matter to an alien spaceship (spoiler: it wasn't).
Controversial Harvard astrophysicist Avi Loeb – who has authored a dizzying number of wide-ranging papers on 'Oumuamua, including claims that it was a piece of light sail technology from a potential past galactic civilization and is thus humanity's first brush with an extraterrestrial artifact – is one of the two scientists who found the 2014 interstellar meteor. In this instance, it appears he was right.
Loeb and co-author Amir Siraj proposed that `Oumuamua was preceded by another interstellar traveler that slammed into Earth's atmosphere in 2014. "One would expect a much higher abundance of smaller interstellar objects, with some of them colliding with Earth frequently enough to be noticeable," they wrote in their 2019 paper.
To see if any of these "smaller interstellar objects" had struck Earth (or at least flown by) recently they pored through observations logged in NASA'S Center for Near-Earth Object Studies (CNEOS) catalog, which notes and calculates asteroid and comet orbits and their potential for Earth impact. To escape the pull of its own star, an interstellar object has to be traveling exceedingly fast, so they narrowed down their search to the fastest objects logged.
One that caught their eye was a fireball that burned up in Earth's atmosphere above Papua New Guinea at 3:05 am local time on January 8, 2014. It had been traveling at a speed of 216,000 kilometers per hour (134,000 miles per hour), much faster than the average meteor orbiting in the Solar System, suggesting it was unbound from the Sun and very possibly "from the deep interior of a planetary system or a star in the thick disk of the Milky Way galaxy". Its speed and trajectory, they wrote, proved with 99 percent certainty the object came from outside the Solar System.
Siraj and Loeb submitted the paper on their discovery to The Astrophysical Journal Letters, but the review process ground to a halt due to missing information that had been withheld from the CNEOS database by the US government.
According to Becky Ferreira for VICE, who broke the story, some of the sensors used to detect near-Earth objects are operated by the US Department of Defence and were therefore classified, which meant Siraj and Loeb couldn't confirm their margin of error on the meteor's speed. After being caught up in legal red tape for nearly three years while pursuing confirmation of that information, Siraj found out the meteor had been confirmed by the US Space Command last week via a tweet from another scientist.
The memo, dated March 1, confirms "the velocity estimate reported to NASA is sufficiently accurate to indicate an interstellar trajectory.” Siraj told VICE they intend to pursue publication of their original study to help scientists discover and study other potential interstellar – and possibly even extra-galactic – visitors.
“Given how infrequent interstellar meteors are, extra-galactic meteors are going to be even rarer,” Siraj told VICE. ”But the fact of the matter is, going forward, we won't find anything unless we look for it."