But where is the rocket now? Here is everything you’ll need to know.

The Long March 5B rocket has dropped into low Earth orbit and there is a high risk of it crashing back down. The European Space Agency said that it expects the re-entry to occur at 3:15am, UTC, which is 1.15pm Saturday AEST.

The agency claims that there is a window of 9 hours and 25 minutes - meaning it could happen either Saturday evening or Sunday afternoon. The 21-ton booster launched part of China's first space station last week.

The launch was the first of 11 missions to construct and provision the space station. The module was propelled by a powerful Long March 5B rocket, whose first stage is currently descending Earthward.

From a low Earth orbit, bodies are drawn gradually by gravity towards the surface of the planet. But the Long March rocket is so massive -- up to 18 tonnes -- that is it unlikely to burn up entirely.

"The Chinese should have anticipated a controlled re-entry with a retrorocket, which is what the Russian did when they removed the Mir station from Earth orbit," explained Nicolas Bobrinsky, head of engineering and innovation at the European Space Agency.

"If the rocket is composed of materials that don't separate on re-entry, it's even riskier," he added. "That would appear to be the case for the Long March 5B."

The most likely landing zone is water, simply because nearly three-quarters of the surface of the planet is covered by oceans.

Even if fragments of the rocket do land on buildings, the speed of impact will be relatively slow at about 200 kilometres per hour (125 miles per hour). By comparison, a meteorite can reach speeds of 36,000 km/hr as it hurtles towards Earth.

What’s happened so far?

April 29

China launched the first of three elements for its station atop the Long March 5B rocket that is now being tracked.

May 6

Calculations of the 21-ton rocket suggest it will fall on May 8.

The US Space Command tracked debris from the spacecraft, which lifted off on May 29 carrying the first module of China‘s new space station.

May 7

The US said it had no plans to shoot down the Chinese rocket plummeting to Earth.

“We have the capability to do a lot of things, but we don‘t have a plan to shoot it down as we speak,” Defence Secretary Lloyd Austin told reporters.

The Pentagon experts expect the body of the rocket to fall sometime on Saturday or Sunday.

Figuring out exactly when and where it will crash is proving difficult.

“We‘re hopeful that it will land in a place where it won’t harm anyone. Hopefully in the ocean, or someplace like that,” Austin said.

The returning rocket is pictured for the first time by Italy-based Virtual Telescope Project

Gianluca Masi, an astronomer who captured the image, explained to Metro: “The sun was just a few degrees below the horizon, so the sky was incredibly bright: these conditions made the imaging quite extreme, but our robotic telescope succeeded in capturing this huge debris.’

“This is another bright success, showing the amazing capabilities of our robotic facility in tracking these objects.”

-- with AFP

This article originally appeared in The Sun and was republished with permission