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Asteroid orbiting the wrong way outed as an 'alien'

The first "immigrant" asteroid from beyond our solar system could hold the key to some big mysteries.

An asteroid lurking near the orbit of Jupiter is the first known immigrant from beyond our solar system to take up permanent residence in our corner of the cosmos. Scientists say the interstellar expat could help us understand how life started on Earth and perhaps in other places too.

Astronomers say the space rock known as 2015 BZ509 is the first to come for a visit and wind up staying.

This asteroid is different from the interstellar visitor 'Oumuamua that made headlines last year when scientists spotted it as it swung through our solar system, apparently for the first time ever, and kept right on cruising by.

Images of 2015 BZ509 in its retrograde orbit that helped scientists determine its far-off origins.

C. Veillet/Large Binocular Telescope Observatory

Unlike 'Oumuamua, 2015 BZ509 was captured by the gravity of our sun and has taken up in a rather unique orbit. 

While every planet in the solar system moves around the sun in the same direction, 2015 BZ509 orbits the other way in a retrograde orbit.

"How the asteroid came to move in this way while sharing Jupiter's orbit has until now been a mystery," said Fathi Namouni of France's Observatoire de la Côte d'Azur in a release. Namouni is lead author of a study on the migrant asteroid published Monday in Monthly Notices of the Royal Astronomical Society: Letters.

After running computer simulations that traced the movements of 2015 BZ509 all the way back to the birth of our solar system, the researchers determined that it could not have been present in that primordial era and must have been captured as it drifted by from elsewhere.

"If 2015 BZ509 were a native of our system, it should have had the same original direction as all of the other planets and asteroids," Namouni said.

The foreign asteroid has likely been in our solar system for quite a while, captured when our sun was still part of a tightly packed star cluster.

"The close proximity of the stars, aided by the gravitational forces of the planets, help these systems attract, remove and capture asteroids from one another," said Helena Morais, a member of the research team from Universidade Estadual Paulista in Brazil.

The researchers are hopeful that studying this first permanent asteroid immigrant could provide new insights about how planets form, how solar systems evolve and maybe even how life emerged on Earth. 

All those revelations also help inform the search for alien life, which may be in the process of emigrating right now.

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