Maaleht reader Sander took the photos and videos shortly before 6 p.m. on Sunday, near Koeru, Järva County, facing toward the Tartu highway.

"At times it resembles a rocket," Sander said, adding an acquaintance had suggested it was "pieces of a Chinese space rocket burning up in the atmosphere" and that it was difficult to judge the event's altitude and distance.

The initial images show a falling object trailed by black smoke, while "Later something keeps dropping with smoke along the edges — not sure if it's a rocket or a plane," Sander said, adding that he called 112, the national emergency number.

Taavi Niittee, leader of the Tõrva astronomy club in South Estonia, said this was most likely an airplane and its condensation trail, or contrail, that Sander saw.

While contrails are common, the current weather conditions, clear but cold and with the long sunsets, can render this everyday sight more unusual-looking, Niittee said, adding: "The unusually dark contrast of the trail against the bright sky is caused by its angle relative to the setting Sun."

In this kind of elongated orientation, a contrail tends to cast a shadow on itself, explaining the unusual appearance, while the aircraft itself could be observed in the video and photos as a bright object at the "lower" end of the trail.

Another tell-tale sign was the slow-moving nature of the object and ensuing trail – while rockets and other space debris burning up are significantly faster-moving phenomena, Niittee said.

Aircraft contrails generally form when warm, moist gases expelled by aero engines meet air as cold as 40 degrees below zero, rapidly condensing into ice crystals, which in turn grow around tiny soot particles left over from jet fuel combustion.

In dry air, the crystals sublimate quickly and the contrail is short-lived; in humid air, the trails last much longer and can grow or change shape under the influence of high-altitude winds.

The presence of aircraft contrails in the skies overhead has in recent years also fueled various conspiracy theories about their true nature.

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