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A reader succeeded in taking this picture of the fireball from the Jubach dam in the Sauerland on Saturday when he wanted to take a time-lapse photo.
"In flight, the object changed from glowing red to a bright green," he writes.
Photo: Michael Erdmann
For some citizens, it was certainly a disturbing phenomenon that they saw at the weekend: A bright beam moved across the sky on Saturday evening, a round ball of fire formed, which glowed for seconds.
One observer reported a greenish color.
The object then disintegrated into several parts high in the sky and was finally no longer visible.
Especially in the southwest of Germany between Cologne, Frankfurt and Stuttgart, the object was discovered in the sky.
"We have a good hundred sightings from this area," says Dieter Heinlein from the German Aerospace Center (DLR).
But DLR also received eyewitness reports about the phenomenon from the north.
And you could even hear the event acoustically.
In Freyung in Lower Bavaria, on the border between Germany, the Czech Republic and Austria, the infrasound station »I26DE« constantly listens for pressure waves below the frequency range that can be heard by humans.
It is part of a worldwide monitoring network of the Organization of the Comprehensive Nuclear-Test-Ban Treaty, with which prohibited nuclear tests are to be detected.
Some of the systems analyze earthquake waves, others listen in the oceans, and others search for radioactive particles in the atmosphere.
And 60 stations like the one in Freyung listen to what is known as infrasound.
The barometers still perceive pressure differences of only one billionth of normal atmospheric pressure.
Explosions, jet jets - or chunks from space can be responsible for vibrations in the air.
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Infrasound signal from the fireball
Photo: bgr
The Federal Institute for Geosciences and Natural Resources (BGR) in Hanover is responsible for the station.
There, at the request of SPIEGEL, they bent over the data from "I26DE" from Saturday.
And BGR expert Christoph Pilger confirms: "At 7:01 pm local time, our station registered a clear infrasound peak from the north-northwest."
The fireball had been observed by observers around 6:40 p.m. in the sky.
The fact that the station only registered it around 20 minutes later is due to the speed of sound, according to Pilger.
In any case, it was "a larger signal" that was "clearly readable."
What kind of celestial phenomenon was that one could not only see but even hear?
Dieter Heinlein from DLR is currently assuming an asteroid fragment that has entered the atmosphere.
He is the technical director of the DLR fireball network, a network of 25 camera stations in Germany, the Czech Republic, Belgium, Luxembourg and Austria that document and investigate such phenomena.
Presumably the sky watchers witnessed a rather rare occurrence.
While most people have seen a meteor popularly known as a falling star, the lighter fireballs aren't that common.
On an annual average, the DLR fireball network only recorded around 30 such events.
In contrast to a normal shooting star, which usually shines for less than a second, a fireball can burn for up to five seconds, and in rare cases even more.
Sometimes the ball changes color or appears to burst at the end of its trajectory.
In the case of falling stars, it is usually only material the size of a grain of dust that is heated by air resistance; in the case of fireballs, also known as bolides, they are massive bodies that hit the atmosphere at speeds of several kilometers per second.
They are made of either stone or metal and are at least one centimeter tall (read more about the differences between the terms here).
Table tennis ball-sized stones from space
When meteors in the sky turn into a ball of fire, this event excites experts.
Because while shooting stars completely burn up in the atmosphere, remnants of the cosmic lump may reach the surface of the earth.
"This is cosmic material that we get delivered free of charge," says Heinlein.
Sometimes there is a chance that not all of the material has been worn out.
That only happened in November when a racing car was sighted over Austria.
But no chunks of this event have yet been found.
Perhaps there are now a few black stones lying around somewhere in Germany that have had a long journey through space.
To find them, the DLR researchers are now evaluating all the information they can get hold of.
First and foremost the camera recordings from your own network, but also the pictures and descriptions from laypeople.
This may result in data on the path of the fireball, which can be used to narrow down possible sites.
The remains of such bolides are a unique testimony to the early phase of our solar system more than four billion years ago, when the planets formed around our central star.
But not all of the matter in the disk of gas and dust around the young star made it to beautiful, round planets.
The gravitational pull of the giant planet Jupiter prevented them from clustering together and so they became misshapen lumps no more than a few hundred kilometers in size.
Hundreds of thousands of them are buzzing around between Mars and Jupiter, in the asteroid belt.
Sometimes they crash into each other and splinter.
And sometimes the force of the impact puts structures made of stone and metal on course towards earth.
Support from "unpaid astronomers"
It is precisely the fresh remnants of this trip that interest researchers like Heinlein.
In contrast to meteorites that were found on Earth at some point, scientists can reconstruct the travel route back to its starting point in the asteroid belt for current events.
But it happens extremely seldom that researchers in Germany find the remains of the alien fragments.
This was achieved in April 2002 when a lump near Neuschwanstein shattered into several fragments at a height of 22 kilometers, of which around six kilograms of material could be collected on earth.
And at Renchen in Baden-Württemberg, astronomy fans also found a few bits and pieces from an event from 2018, a stroke of luck for science.
In this context, Heinlein expressly appreciates the work of laypeople on whom science depends.
Not every entry into the atmosphere is documented by a camera.
Therefore, it is important when amateur researchers make their data available.
He doesn't like the term, however, because space enthusiasts often work very professionally.
"Actually, they're unpaid astronomers," he says.
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