Originally published 2017-11-29.
Still from Tony Bateman's aurora camera / YouTube
On the evening of Thursday 16 November 2017, at about 18:40 local time, an exceptionally bright fireball crossed the sky over Inari in Finnish Lapland. For a few seconds the snowy landscape lit up as if it were daytime, and an aurora webcam happened to be recording. Witnesses described a flash that changed colour, and some reported a loud bang and shaking buildings. Astronomers later concluded that it was a large meteor, a natural space rock burning up in the atmosphere, and that some fragments probably reached the ground in a remote wilderness area.
Here is what happened, what the videos show, and how events like this are studied.
What people saw and heard
The most widely shared footage came from Tony Bateman, who runs the tour company Aurora Service Tours and keeps a live camera pointed at the northern sky to catch the aurora borealis. The camera was set up in the Muotkatunturi wilderness area in Utsjoki, north of Inari.
Bateman wrote in his video description that he was sitting in the cottage when there was a huge bang and the building shook. Guessing that the camera might have caught something, he rewound the stream and found the flash. His reaction, in his own words: "Absolute goosebumps at this stage. What a night!"
Tony Bateman's aurora-camera recording of the fireball
Atle Staalesen, a journalist with the Barents Observer, was driving about 10 km north of Inari at the time. He described the sky turning reddish, then bluish, before a brilliant white burst that lit everything around him, "like a massive explosion that lasted for some five, six seconds." Inside his car he heard nothing, though other witnesses reported bangs.
Local media in Finnish Lapland and northern Norway took calls from worried residents. The light was reportedly visible across Lapland and as far as Troms and Finnmark in Norway, and some reports said it was noticed in northwest Russia too.
Was it really a meteor?
In the first hours people suggested all sorts of explanations: fireworks, a crashing plane, or a failed missile. The guesses were not absurd. Finland was holding a military exercise in Lapland that week, although the firing range was roughly 300 km to the south.
Experts quickly settled on a natural cause. Jyrki Manninen, a space physics engineer at the University of Oulu, told the Finnish broadcaster YLE that the footage pointed to a meteor, most likely a fairly big rock. The colour changes, the brief duration and the sudden terminal flash are all typical of a large meteoroid breaking apart.
Another recording of the same event
Meteor, fireball, bolide, meteorite: the terms
These words are often mixed up, so it helps to separate them:
- Meteoroid: the rock or dust particle while it is still in space.
- Meteor: the streak of light produced when it enters the atmosphere and heats the air around it.
- Fireball: a very bright meteor, brighter than the planet Venus. The American Meteor Society uses magnitude -4 as the threshold.
- Bolide: a fireball that ends in a bright terminal flash, often as the object fragments. The Lapland event fits this description.
- Meteorite: any piece that survives the trip and lands on the ground.
Most meteors glow at heights of around 80 km or more. Larger objects can penetrate deeper, and once they slow down they stop glowing at roughly 15 to 20 km, falling the rest of the way dark.
Did any of it reach the ground?
A week after the event, the Ursa Astronomical Association, Finland's main amateur astronomy society, published its analysis based on the videos and witness reports. Its modelling suggested the object weighed a few hundred kilograms before it hit the atmosphere. Most of that mass was destroyed on entry, but Ursa estimated that tens of kilograms of fragments came down in the Vätsäri wilderness area, northeast of Lake Inari. Earlier guesses had placed the fall in the lake itself, which would have made recovery almost hopeless.
Ursa's Esko Lyytinen noted that most meteorites weigh between a few hundred grams and a few kilograms, so a fall of this size would be unusual. Searching, however, had to wait. The polar night, deep snow and rough terrain made a winter search impractical, and the association said it would try again after the thaw.
How common are fireballs like this?
More common than most people think. The American Meteor Society estimates that several thousand fireball-class meteors enter the atmosphere every day, but most happen over oceans, uninhabited land or in daylight, so they go unseen. Somewhere between 10 and 50 meteorite-dropping events are thought to occur daily worldwide, and only a handful of falls are actually witnessed each year.
The Lapland fireball was special because it was bright, happened over land at night, and was caught on cameras that were already running. Dashboard cameras, security cameras and dedicated all-sky networks have made such recordings far more common since the 2010s, and multiple views from different places allow scientists to triangulate a trajectory and estimate where fragments might land.
About the sounds: genuine sonic booms can reach the ground from very bright fireballs that break up below about 50 km, but because sound travels slowly they arrive a minute or more after the flash. Witnesses who hear a bang at the same instant as the light are describing something more debated, sometimes called electrophonic sound, which has not been firmly explained.
Chelyabinsk: the reminder of what a bigger rock can do
The Lapland object was small. The comparison many people reached for was Chelyabinsk in Russia, where on 15 February 2013 a meteor about 18 metres across and weighing roughly 10,000 tonnes exploded about 30 km up. It went undetected before entry, partly because it approached from the direction of the Sun. Its shock wave damaged more than 7,200 buildings, and about 1,500 people sought medical help, almost all because of broken glass. Nobody died.
Events on that scale are rare, perhaps once in decades, and space agencies now run dedicated surveys to find larger near-Earth objects well in advance. Small rocks like the one over Inari are a regular part of Earth's environment and pose no meaningful risk.
If you see a fireball
Note the time, the direction it travelled, how long it lasted, its colours and whether it broke up, and listen for a few minutes afterwards for any delayed boom. Then report it to a national network; in Finland the Ursa association collects sightings, and internationally the American Meteor Society and the International Meteor Organization collect reports. Many reports together are what make it possible to find meteorites.
Sources: The Barents Observer, November 2017: Atle Staalesen's eyewitness account; Eye on the Arctic (RCI), 23 November 2017: fragments of meteor fell in the Vätsäri wilderness area; American Meteor Society: Fireball FAQs; Wikipedia: Chelyabinsk meteor; video by Tony Bateman, Aurora Service Tours; first reported in English by IFLScience.
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