Back in 2017, a point of strange light flashed through the solar system. Three years later, a team of scientists claims to have figured out what it was.

That light was the first interstellar visitor ever detected in solar space. Scientists put forth several eye-popping theories from that brief glance: Maybe it was a piece of discarded alien technology. Maybe it was a cosmic dust bunny, made of incredibly fragile frozen hydrogen. Now, another team of researchers claims to have cracked the problem of ‘Oumuamua: It was a nitrogen iceberg, they argue, snapped off from a frigid alien Pluto.