Video screenshot by Eric Mack/CNET

Last month an ancient Indonesian caldera rumbled once again, but not because of any unexpected volcanic activity.

On July 18, a strange metal object fell out of the sky and impacted the eastern shore of Lake Maninjau, which fills the caldera today.

"We were all very shocked when we heard the loud sound, so we followed the sound and ended up finding the exact position of where it fell," a 30-year-old man from the area named Sidik told Indonesian news site Tempo.co.

The object appears to be a piece of space junk, probably a fuel tank from a Chinese Long March 3A rocket, according to amateur astronomer Muh Ma'rufin Sudibyo, who wrote a detailed break down of the hollow, egg-shaped detritus' fall from space.

The hunk of junk has been sent to the science center of Indonesia's National Institute of Aeronautics and Space (LAPAN) for identification, but Sudibyo used the time and location of the object's fall, along with data from a satellite tracking service, to trace it back to the upper stage of a Chinese rocket used to launch a GPS satellite back in 2007.

Sudibyo explains that the rocket stage likely spent the last decade in a very irregular and volatile orbit pulling it ever closer to the point of re-entering Earth's atmosphere, which finally happened last month.

Fortunately no one was hurt when the 3.6-foot (110 cm) long, 16 pound (7.4 kg) tank smashed down on West Sumatra. But this isn't the first time the large island nation has been bombarded by space trash. Just last year, parts of a SpaceX rocket rained down upon the country.

Of course, space junk is an ever increasing problem elsewhere too. We've seen it threaten satellites currently in orbit and inspire no fly zones when it's possible to track its dramatic return from Earth.

But as Sudibyo points out, given Indonesia's location along the equator, directly below where many satellites in geostationary orbit hang out, keeping one eye on the sky is always a good idea there.

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