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Unusual Asteroid Could Be An Interstellar Guest To Our Solar System

Researchers postulate that a peculiar asteroid spotted near Jupiter is a permanent guest from a completely different solar system.

In an article published Monday in the U.K.’s Monthly Notices of the Royal Astronomical Society, the researchers say their studies indicate that asteroid 2015 BZ509 (nicknamed BZ) is actually an “interstellar immigrant” that has been circling the sun ever since our solar system formed about 4.5 billion years ago.

One of the researchers, Fathi Namouni of France’s Côte d’Azur Observatory, told HuffPost that would make the discovery the first of its kind. 

“There is no other asteroid in the solar system that moves around the sun and is known to have been born outside the solar system,” he wrote in an email. 

Scientists Fathi Namouni of Côte d'Azur Observatory in France and Helena Morais of São Paulo State Universi

BZ was discovered in 2014, according to The New York Times. The asteroid, a little less than two miles wide, is located near Jupiter and circles the sun every 11.6 years.

Scientists noticed that BZ has an unusual orbit. Instead of circling around the sun in the same direction as Jupiter, BZ has a retrograde orbit, meaning it circles the sun in the opposite direction. 

Namouni and the co-author of Monday’s article, Helena Morais of Brazil’s Universidade Estadual Paulista, were curious about why the asteroid moved in this unusual way. Using a time machine-like simulation, they recreated BZ’s possible movements over the past 4.5 billion years using their knowledge of the asteroid’s current orbit. 

“Surprisingly we found going back 4.5 billion years in the past, that the asteroid was moving exactly where it is now,” Namouni wrote. “But at 4.5 billion years in the past, all solar system objects, planets, asteroids and comets moved exactly in the same direction around the sun. This tells us that the asteroid was not born in the solar system but captured from outside it.”

Other astrophysicists have come up with alternate explanations for BZ’s retrograde orbit and suggested, for example, that the object could have come from the Oort Cloud, an icy mass of debris that some astronomers propose exists near the outer reaches of the solar system. Others say BZ could have come from Planet Nine, a hypothetical, hidden planet that some claim could lie beyond the dwarf planet Pluto. 

Regardless, Namouni believes BZ holds a wealth of information for scientists. Its relative proximity to Earth means scientists could analyze an object potentially from an alien solar system without needing to leave our own. Namouni said a robotic mission to BZ is “perfectly possible” with current technology.

Analyzing the asteroid’s chemical composition could help scientists understand how our own solar system formed ― and even provide insights into the origin of life. For example, if scientists discover that BZ contains water, it could signal that interstellar asteroids can deliver water to Earth and “hence indirectly contribute to the appearance of life,” Namouni wrote.

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