In 2017, scientists announced that they had, for the first time, detected an object from interstellar space zipping through our solar system—a football-field sized asteroid dubbed ‘Oumuamua. Now, as Charles Q. Choi reports for Space.com, Harvard astronomers say they have found evidence that another, considerably smaller interstellar space rock made it into our solar system in 2014—and that this one collided with Earth.
Astrophysicist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and Amir Siraj, a Harvard astronomy undergraduate, suspected that if a large asteroid like ‘Oumuamua could travel from another star system, smaller objects might be making the journey, too. Some might even collide with Earth “frequently enough to be noticeable,” they write in a paper submitted to the journal Astrophysical Journal Letters.
Researchers had previously identified ‘Oumuamua as an interstellar body because its trajectory and high speed—54 miles per second— indicated it was not gravitationally bound to the sun. So Loeb and Siraj searched for the fastest meteors detected by U.S. government sensors over the past 30 years and catalogued by the Center for Near-Earth Object Studies.
They hit upon three possibilities and disregarded two due to lack of data. But the third meteor, which had disintegrated above the northeast coast of Papua New Guinea in January 2014, is a promising candidate for an interstellar visitor, Loeb and Siraj contend. The object was three feet wide, with an altitude of 11.6 miles, and had been traveling at a speed of 37 miles a second, reports National Geographic’s Nadia Drake.
“[I]t was traveling so fast that it must have been unbound from the solar system—meaning that it, like ‘Oumuamua, originated from outside of the solar system,” Siraj tells Newsweek’s Hannah Osborne. The researchers think it may have come from the “deep interior of a planetary system,” according to the paper, or from a star in a component of the Milky Way known as the thick disk.
But other experts aren’t so sure. “The result is interesting, but rests upon measurements for a single event,” Eric Mamajek of NASA’s Jet Propulsion Laboratory tells Lisa Grossman of Science News. “Was the event a statistical fluke or an actual interstellar meteor?”
The new paper still hasn’t been peer-reviewed, so it remains to be seen whether Loeb and Siraj’s findings will be confirmed by the journal. But for now, the scientists say that their research suggests small interstellar meteors could be colliding with Earth relatively frequently, possibly once every ten years, reports Grossman. And if experts can spot one of these objects before it burns up in the atmosphere—perhaps by setting up an alert system that fixes telescopes on fast-moving meteors—they may be able to analyze the objects’ gaseous debris.
"From that,” Loeb tells Choi, “we could infer the compositions of interstellar meteors.”