To see where the stars are falling, maybe it’s time to look underground.

A Johns Hopkins University researcher published a study in the journal Science on Thursday outlining a method that uses seismometers to track space debris as it falls to Earth, according to the university.

Thousands of human-made objects — satellites, old rocket boosters, that sort of thing — have been abandoned in Earth’s orbit.

When what gets sent up must come down, that space junk can cause significant risk to life on the ground, and not just from the initial impact.

But Earth is big and debris is small, so it can be hard to track where exactly things from orbit land.

Benjamin Fernando, a postdoctoral research fellow at Hopkins, developed a new technique for tracking debris as it falls with a colleague at Imperial College London. Using existing seismometers, it takes advantage of the sonic booms produced by falling debris.

“Re-entries are happening more frequently,” Fernando said in a news release. “This is a growing problem, and it’s going to keep getting worse.”

Depending on what the debris is made of, it can shoot off toxic plumes as it breaks up in the atmosphere, or it can carry radioactive material. Objects of “moderate size” reenter Earth’s atmosphere about once a week, according to the European Space Agency.

Scientists can use radar data to track an object as it drops in low Earth orbit and then predict where it enters the atmosphere.

But those predictions, Fernando and his colleague Constantinos Charalambous said, can be off by “thousands of miles” in the worst cases.

If officials want to find debris that’s fallen to Earth and contain any potential contaminants, Fernando said, “It matters whether you figure out where it has fallen quickly — in 100 seconds rather than 100 days, for example.”

How to catch a falling star

A 1.5-ton piece of orbital debris from a Chinese spacecraft reentered the atmosphere on April 2, 2024, streaking through the sky as it burned up.

The module, which was debris from a mission two years earlier that carried three taikonauts to China’s space station, was large enough that it could pose a threat to people, according to the researchers.

Space junk falling back to Earth moves faster than the speed of sound, creating sonic booms. Vibrations from the trail of a sonic boom travel to the ground and are noticeable on seismometers, which are usually used to detect and measure earthquakes.

Researchers are able to map out the activated seismometers to follow the path of debris and estimate where it landed, Hopkins said in a news release.

In the case of the April 2024 debris, Charalambous and Fernando analyzed data from 127 seismometers in Southern California and determined the object was traveling northeast over Santa Barbara and Las Vegas at a cruising speed between Mach 25 and Mach 30, faster than any jet.

By looking at seismometer readings and using other calculations for trajectory, speed and altitude, the researchers estimated the module was traveling about 25 miles south of the trajectory that U.S. Space Command had predicted using orbital measurements.

Reentry predictions can be off by thousands of miles, the researchers said. Seismic data can be a complement to radar data, tracking where an object travels once it enters the atmosphere.

Seismometers provide near-real-time tracking, the researchers said, which would allow authorities to quickly retrieve objects that reach the ground.

Fernando pointed to a recent case in Chile, where scientists discovered artificial plutonium in a glacier, as an example of how better tracking could have helped.

Scientists believe it’s evidence that the Russian Mars 96 spacecraft, which fell out of orbit in 1996, broke apart as it fell toward the ocean, and that its power source burst open and contaminated the area, Fernando said.

The actual location of the debris has never been confirmed, he said. Scientists had until recently thought that it burned up during reentry, but that its radioactive power source crashed to the ocean in one piece.

“We’d benefit from having additional tracking tools, especially for those rare occasions when debris has radioactive material,” Fernando said.

Talk about wishing upon a star.