A string of lights that lobbed across the night sky in parts of the U.S. on Wednesday, Thursday and Friday had some people wondering if a fleet of UFOs was coming, but it had others— mostly amateur stargazers and professional astronomers— lamenting the industrialization of space.

A large segment of a Chinese rocket re-entered the Earth's atmosphere and disintegrated over the Indian Ocean on Sunday, the Chinese space agency said, following fevered speculation over where the 18-tonne object would come down.

Officials in Beijing had said there was little risk from the freefalling segment of the Long March-5B rocket, which had launched the first module of China's new space station into Earth orbit on April 29.

But the US space agency NASA and some experts said China had behaved irresponsibly, as an uncontrolled re-entry of such a large object risked damage and casualties.

"After monitoring and analysis, at 10:24 (0224 GMT) on May 9, 2021, the last-stage wreckage of the Long March 5B Yao-2 launch vehicle has re-entered the atmosphere," the China Manned Space Engineering Office said in a statement, providing coordinates for a point in the Indian Ocean near the Maldives.

China's rogue rocket is in an uncontrolled free-fall towards Earth and no one knows where or exactly when it will burn through Earth's atmosphere, but the risk of debris hitting an inhabited area remains very small, experts told AFP Friday.

What happened?

On April 29, China launched the first module of its "Heavenly Palace" space station, a milestone in Beijing's ambitious plan to establish a permanent human presence in space.

The module was propelled by a powerful Long March 5B rocket, whose first stage is currently descending Earthward.

If Chinese ground engineers have no control over the booster stage's trajectory, it is not due to a technical failure or some unexplained glitch. The rocket was designed that way.

From a low Earth orbit, bodies are drawn gradually by gravity towards the surface of the planet.