The rocket booster can be seen tracking across the sky from right to left
An abandoned part of a rocket is hours away from crashing into the Moon, say scientists who first predicted the collision in January.
The three-ton rocket part, hurtling through space at 5,800 mph, is expected to strike at 12:25 GMT Friday.
Astronomers initially thought the rocket part was launched by Elon Musk’s SpaceX program, then said it was Chinese, which China denies.
Scientists hope to study the 10–20 m wide crater and the plumes of lunar dust created during the impact.
The rocket part was first seen from Earth in March 2015. A Nasa-funded space survey in Arizona spotted it, but quickly lost interest when it was shown that the object was not an asteroid.
The rocket part is what is known as space junk — material discarded from missions or satellites without enough fuel or energy to return to Earth. Some parts are closer to us, just above Earth, but others, like this booster, are thousands of miles away in high orbit, far from Earth’s atmosphere.
The European Space Agency estimates that there are now 36,500 pieces of space debris larger than 10 cm.
No space program or university officially tracks deep space debris. Space monitoring is expensive and the risk to humans from high orbit debris is low.
Thus, it falls to a tiny handful of volunteer astronomers who spend their free time making calculations and estimating orbits. They send emails and alerts back and forth, asking whoever is in the best spot on the planet to spot an object in space.
His telescope picked up a tiny point of light moving across the sky. Calculations suggested it was part of a rocket, he told BBC News.
Space debris falls and disappears, often unpredictably. For seven years, he barely saw the rocket — until in January, it reappeared.
“I took some pictures when it passed near Earth,” he explained.
He sent his photos to astronomer and data scientist Bill Gray on the U.S. East Coast. It was the expert who then identified it as a SpaceX booster heading to the Moon.
The news that an abandoned part of one of billionaire Musk’s space missions was going to hit the Moon made global headlines.
But tracking space debris is often “detective work,” Gray says. The rocket’s insignia can’t be seen — astronomers must piece together its identity by tracking its route backwards through space. They then match its orbit to the dates and locations of rocket launches and trajectories.