Earth may already have been visited by an object from outside our solar system — a meteor that burned up in the planets atmosphere in 2014, astronomers claim. If confirmed, it would be the first known interstellar object to have entered the atmosphere.
The first interstellar visitor known to have come close to Earth was the roughly 400-meter-wide asteroid named Oumuamua. It swooped within about 24 million kilometers of the planet in October 2017 (SN: 11/25/17, p. 14). Its sharp-angled approach to the solar system and equally strange departure led astronomers to suggest that Oumuamua could have been anything from a fluffy skeleton of a comet to an alien spaceship (SN Online: 2/27/19).
If there was one interstellar interloper, astronomers reasoned, there would likely have been more, including some that collided with Earth.
So astronomer Avi Loeb and undergraduate student Amir Siraj, both of Harvard University, searched through a NASA catalog of meteors that have burned up in Earths atmosphere to see if any had taken an odd, Oumuamua-like trajectory.
The pair identified a 0.9-meter-wide object that disintegrated in January 2014 in the sky over the South Pacific, off the northern coast of Papua New Guinea. The meteor had approached the sun at a brisk 60 kilometers per second, suggesting that it wasn't bound by the sun's gravity. Running that meteors orbit back in time shows that the object probably originated outside of the solar system, possibly in the inner part of another planetary system in the thick disk of the Milky Way, the astronomers report online April 15 at arXiv.org.
That origin could mean that the object came from another stars habitable zone — the region around a star where temperatures are right for liquid water, and perhaps life, to exist. “If an interstellar object comes from another planetary system, it can bring life into the solar system from outside,” Loeb says.
This particular object was so small that it burned up in Earths atmosphere, so it couldnt have delivered microbes to Earths surface, the team says. But because the duo found just one interstellar meteor in a decades-spanning database, Loeb and Siraj estimate that Earth could be struck by one every 10 years. That would mean about 450 million interstellar meteors might have hit Earth across its roughly 4.5-billion-year hisRead More – Source
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