Scientists discovered the first known interstellar meteor to ever hit Earth, according to a recently released US Space Command document. An interstellar meteor is a space rock that originates from outside our solar system – a rare occurrence.
The discovery came as a surprise to Amir Siraj, who identified the object as an interstellar meteor in a 2019 study he co-authored while pursuing a bachelor’s degree at Harvard University.
Siraj studied ʻOumuamua, the first known interstellar object in our solar system, which was found in 2017, together with Abraham Loeb, a professor of science at Harvard University.
Siraj decided to go through NASA’s Center for Near Earth Object Studies database to find other interstellar objects and found what he thought was an interstellar meteor within days.
A need for speed
The high speed of the meteor is what originally caught Siraj’s eye.
The meteor moved at a high speed of about 28 miles per second (45 kilometers per second) relative to Earth, which moves at about 18.6 miles per second (30 kilometers per second) around the sun. Because scientists measured how fast the meteor was moving on a moving planet, 45 kilometers per second was actually not how fast it went.
The heliocentric velocity is defined as the velocity of the meteor relative to the sun, which is a more accurate way of determining the orbit of an object. It is calculated from the angle at which a meteor hits the Earth. The planet is moving in one direction around the sun, so the meteor could have hit the Earth frontally, meaning the opposite direction the planet is moving, or from behind, in the same direction as the Earth is moving.
Since the meteor hit Earth from behind, Siraj’s calculations said the meteor actually traveled at about 37.3 miles per second (60 kilometers per second) relative to the sun.
He then mapped the orbit of the meteor and found that it was in an unbound orbit, as opposed to the closed orbit of other meteors. This means that instead of circulating around the sun like other meteors, it came outside the solar system.
“Presumably it was produced by another star, was thrown out of that star’s planetary system and happened to come our way to our solar system and collided with Earth,” Siraj said.
Hard to get published
Loeb and Siraj have not been able to get their results published in a journal because their data came from NASA’s CNEOS database, which does not reveal information such as how accurate the readings are.
After several years of trying to get the necessary additional information, they received official confirmation that it was in fact an interstellar meteor, from John Shaw, deputy commander of the US Space Command. The command is part of the U.S. Department of Defense and is responsible for military operations in outer space.
“Dr. Joel Mozer, Chief Scientist of Space Operations Command, U.S. Space Force’s service component in the U.S. Space Command, reviewed the analysis of additional data available to the Department of Defense in connection with this finding. Dr. Mozer confirmed that the velocity estimate reported to NASA is accurate enough to indicate an interstellar orbit, “Shaw wrote in the letter.
Siraj had switched to other research and had almost forgotten his discovery, so the document came as a shock.
“I thought we would never learn the true nature of this meteor, that it was just blocked somewhere in government after our many attempts, and so actually seeing that letter from the Department of Defense with my eyes was a truly incredible moment,” he said. Siraj.
Since receiving the confirmation, Siraj said his team is working on resubmitting their findings for publication in a scientific journal.
Siraj would also like to put a team together to try to pick up part of the meteor that landed in the Pacific, but admitted it would be an unlikely option due to the large size of the project.
If scientists were able to get their fingers in the “holy grail of interstellar objects,” Siraj said it would be scientifically groundbreaking in helping scientists discover more about the world outside our solar system.
NASA and the US Space Command did not initially respond for comment.