From Popular Mechanics
Two years ago, our solar system received an unexpected visitor from elsewhere in the galaxy. Astronomers spotted the asteroid 'Oumuamua, which likely originated outside of our solar system, passing through on its way to who knows where. But now researchers claims that it wasn't the first: Another interstellar asteroid actually crashed into the Earth in 2014.
What initially set 'Oumuamua apart from every other asteroid we've ever seen is how quickly it was moving. The asteroids in our own solar system are gravitationally bound to the Sun, limiting how fast they can possibly move. Even the fastest asteroids have a speed limit they can never exceed.
'Oumuamua, however, has none of those restrictions. When astronomers saw it rocketing through our solar system, they knew it was likely born around a different star than our own. Now, those same astronomers realized they could apply that same test to other observed asteroids, starting with ones that burned up in our planet's atmosphere.
Combing through a database of thousands of meteor sightings, the researchers managed to identify one from 2014 that fit their criteria. This meteor crashed into the Earth on January 8 in the South Pacific, and was traveling a remarkable 134,200 miles per hour. That puts it well outside the possible speed of a solar system asteroid. Furthermore, its trajectory indicated it came from outside our solar system.
This makes this particular meteorite the first interstellar visitor we have records for, but it's almost certainly not the first interstellar visitor we've ever had. The researchers estimate that an interstellar asteroid likely crashes into the Earth once a decade or so, and that our solar system is probably filled with them. Most, of course, are too small for us to find, but if we keep waiting eventually another one is bound to hit us.
With luck, the asteroid that hits us will be big enough to reach the ground, and we'll be able to hold an interstellar asteroid in our own hands. That's probably the only way we'll ever get to see a piece of the wider cosmos up close, and we could use it to learn a great deal about the rest of the universe. It's unlikely to actually happen, but it's a nice dream.
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