In October 2017, ‘Oumuamua was discovered passing through our Solar System and close to the Earth. Since then, there have been a multitude of studies and speculations on the object, some even suggesting that it was an alien spacecraft.

Last year, an international team of 14 astronomers gathered in Switzerland to critically review what was known about ‘Oumuamua. The team was co-led by Professor Alan Fitzsimmons and included Dr Michele Bannister, both from Queen’s University Belfast.

The experts looked at the size, shape and composition of the object. They also focused on where it came from, if there were others like it and if it was entirely natural or an artificial alien probe.

Professor Alan Fitzsimmons from Queen’s University Belfast commented: “This was our first close encounter with a large object from another star system, and while we expected to find such an object at some point, the science community is still debating its exact nature.

“We found that we do not need to assume it is artificial as speculated by some, everything we see points to a natural origin. But that doesn’t detract from the wondrous nature of being visited by a piece of another Solar system.”

The findings are published in Nature Astronomy.

While ‘Oumuamua was the first object from another star system larger than a grain of sand to be found, the team concluded that it is plausible that small interstellar worlds are abundant. Some 10,000 may be passing through our Solar System at any time.

The team also noted there are many questions still to answer, including the exact shape of ‘Oumuamua, and how its rotation was affected by outgassing of ices during its passage close to our Sun. It is also possible that the home Sun of ‘Oumuamua will never be identified among the 100 billion stars of the Milky Way.

A new UK-led mission just approved by the European Space Agency for launch in 2028, named Comet Interceptor, will help to answer some of these questions. The mission will either visit a yet-to-be-discovered interstellar object or a comet from the far reaches of the Oort cloud.

Dr Michele Bannister from Queen’s University Belfast is involved in the Comet Interceptor mission. She said: “More cousins of ‘Oumuamua will be found by the big new sky surveys, particularly the Large Synoptic Survey Telescope, potentially years before these little worlds come close to the Sun — and next time, we may be able to go visit one up close!”

Dr. Matthew Knight from the University of Maryland and co-lead of the team, said: “In the next ten years, we expect to begin seeing more objects like ‘Oumuamua. We may start seeing a new object every year. If we find 10-20 of these things and ‘Oumuamua still looks unusual, we’ll have to reexamine our explanations.”

Meanwhile, research into the first interstellar visitor continues. Already, Michele Bannister has collaborated with another astronomer, Susanne Pfalzner at the Jülich Supercomputing Center in Germany, to show that bodies like ‘Oumuamua may be the `seeds’ from which Earth-like planets are born.

The research was supported by the International Space Science Institute in Bern, Switzerland, and by funding from the UK’s Science and Technology Funding Council.

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