Oumuamua is not an alien spaceship! First interstellar object to pass through solar system found to be of natural origin

Oumuamua is not an alien spaceship! First interstellar object to pass through solar system found to be of natural origin

Putting an end to speculation, scientists have concluded that the first known interstellar object to visit the solar system is not an alien spacecraft. The cigar-shaped object, named ‘Oumuamua, is of “natural origin,” shows a new analysis by a team of astronomers, co-led by the University of Maryland (UMD).

“The discovery of the first interstellar object passing through the Solar System, 1I/2017 U1 (‘Oumuamua), provoked intense and continuing interest from the scientific community and the general public. The faintness of ‘Oumuamua, together with the limited time window within which observations were possible, constrained the information available on its dynamics and physical state. Here we review our knowledge and find that in all cases, the observations are consistent with a purely natural origin for ‘Oumuamua,” say the research team in their findings.

Object’s Odd Characteristics had Baffled Scientists

Discovered October 19, 2017, the interstellar visitor baffled scientists across the world. First spotted by the Panoramic Survey Telescope and Rapid Response System 1 (PanSTARRS1) telescope - located at the University of Hawaii's Haleakala Observatory - the object defied easy description, simultaneously displaying characteristics of both a comet and an asteroid.


It was ‘Oumuamua’s odd and unique characteristics that had led to widespread interest and speculation the object could be an alien spacecraft, sent from a distant civilization to examine our star system. Astronomers formally named the object 1I/2017 U1 and appended the common name ‘Oumuamua, which roughly translates to ‘scout’ in Hawaiian.

Scientists had never seen anything like it in the solar system and hence, researchers from across the world raced to collect as much data as possible before ‘Oumuamua traveled beyond the reach of Earth's telescopes. They only had a few weeks to observe the strange visitor.

“Its faintness meant that most observations were restricted to the first week post-discovery. Yet because the existence of these objects had been anticipated for decades, within weeks, a wealth of papers had already been published, and the literature continues to expand rapidly as researchers in diverse fields consider its implications. The astronomical community (and the general public) remain excited with interest in ‘Oumuamua,” says the ‘Oumuamua team.


Object Remains a Mystery, but Analysis Suggests Natural Phenomena

‘Oumuamua is red in color, similar to many small objects observed in our solar system, but this is where the familiarity ends, reveals the first comprehensive analysis and the best big-picture summary to date of what is known about the object. The researchers describe in the paper that ‘Oumuamua likely has an elongated, cigar-like shape and an odd spin pattern, much like a soda bottle laying on the ground, spinning on its side. Its motion through the solar system, say the researchers, is particularly puzzling. They say while it appeared to accelerate along its trajectory - which is a typical feature of comets - one could not find any evidence of the gaseous emissions that typically create this acceleration.

In this artist's concept, the interstellar object ‘Oumuamua is depicted as a cigar-shaped body. (ESO/M. Kornmesser)


“The motion of ‘Oumuamua did not simply follow gravity along a parabolic orbit as we would expect from an asteroid. But visually, it has never displayed any of the comet-like characteristics that are expected. There is no discernable coma - the cloud of ice, dust and gas that surrounds active comets - nor a dust tail or gas jets,” says the research team in their findings.

Matthew Knight, an associate research scientist in the University of Maryland Department of Astronomy, worked with Alan Fitzsimmons, an astronomer at Queen's University Belfast in Northern Ireland, to assemble a team of over ten astronomers from the U.S. and Europe. The International Space Science Institute (ISSI) in Bern, Switzerland, served as a virtual home base for the collaboration. 

The new research paper is primarily an analysis of existing data, including a December 2017 study of 'Oumuamua's shape and spin pattern, co-authored by Knight and a team of UMD astronomers. The previous analysis relied on data from the Discovery Channel Telescope (DCT) at the Lowell Observatory in Arizona. The University of Maryland is a scientific partner of the DCT, along with Boston University, the University of Toledo and Northern Arizona University.

The researchers say while the object is weird and hard to explain, but that does not exclude other natural phenomena that could explain it. Knight, Fitzsimmons and their colleagues considered several mechanisms by which ‘Oumuamua could have escaped from its home system. For example, they say, the object could have been ejected by a gas giant planet orbiting another star. According to theory, Jupiter may have created the “Oort cloud” - a massive shell of small objects at the outer edge of the solar system - in this way.


Some of those objects, the findings say, may have slipped past the influence of the sun's gravity to become interstellar travelers themselves. They conclude that while it continues to remain a mystery, the team will stick with "analogs" they that know of, unless or until they find something unique. 

More Interstellar Objects Expected to be Discovered

The research team suspects ‘Oumuamua could be the first of many interstellar visitors. The group says it is possible that another one to two interstellar objects will be discovered in the next four to five years, after which it is anticipated that future large surveys like the Large Synoptic Survey Telescope (LSST) will find approximately one per year. The LSST is scheduled to be operational in 2022.

The researchers say the LSST will be leaps and bounds beyond any other survey, in terms of capability, to find small interstellar visitors. The team says once they start seeing a new object every year, that is when scientists will be able to tell whether ‘Oumuamua is weird, or common. The researchers add that if they can observe 10 to 20 of these objects, and ‘Oumuamua still looks unusual, they will have to re-examine their explanations.


The current study titled The Natural History of 'Oumuamua was published on July 1 in the journal Nature Astronomy.

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