13th May 2023 | Places, Tech stuff

Oumuamua. What was the large strangely shaped object that recently visited our solar system from outer space?

On October 19, 2017, interstellar object, ‘Oumuamua—a Hawaiian term that translates to scout—was discovered by the Pan-STARRS survey. Astronomers first spotted the object as it passed through the inner solar system on a slingshot trajectory around the sun that would send it hurtling back into interstellar space. The brief visit gave only a few weeks for researchers to study ‘Oumuamua before it disappeared from view.

The object also apparently somehow accelerated away from the sun.  

Current thoughts on ‘Oumuamua

More than five years after the object’s discovery, researchers are still struggling to comprehend the few observations they were able to make. Especially those that revealed ‘Oumuamua moving more rapidly away from the sun than gravity alone could explain. Against all expectations, the object had somehow accelerated as it departed, like a spooked driver speeding away from a seedy part of town. Let’s face it – Earth is certainly getting more seedier!!

However, scientists have a new idea to explain this enigmatic behavior of our solar system’s first known interstellar visitor.

In a paper published this year on March 22 in Nature, two researchers say the unexpected acceleration may have been caused by the propulsive effect of hydrogen gas billowing from the sun-warmed object’s surface of water ice. The hypothesis would strengthen the case that it was not some wierd one-of-a-kind object but rather a natural comet-like body.

But previous work has shown that sublimating water ice alone couldn’t provide enough push to explain ‘Oumuamua’s acceleration. The authors of the paper hence added an additional step. As the object traveled through interstellar space, energetic cosmic rays battered its surface and broke apart some of its water ice to form hydrogen. Rather than escaping to space, most of the hydrogen remained locked within the surrounding ice. But as ‘Oumuamua approached our star, sunlight warmed and released the trapped hydrogen from its water-ice cage to create the extra acceleration.

With the icy interloper long gone, there is no way to test the claims offered by this new research. You can say anything you want about this object because it will never be seen again.

Another extreme view about ‘Oumuamua

There was another explanation from Harvard University astrophysicist Avi Loeb.

To Loeb, the most plausible explanation was as obvious as it was sensational: taken together with its possibly pancakelike shape and high reflectivity, ‘Oumuamua’s movement made perfect sense if the object was in fact a light sail—perhaps a derelict from some long-expired galactic culture.

In late 2018 Loeb and his co-author Shmuel Bialy, a Harvard postdoctoral fellow, published a paper in the Astrophysical Journal Letters arguing that ‘Oumuamua had been nothing less than humanity’s first contact with an artifact of extraterrestrial intelligence.


No matter what this interstellar visitor was, it remains something of an enigma. The fact that it is destined not to return ensures that it will probably be forgotten. I guess it all remains in the eye of the scientific beholder and the particular slant he/she may put upon it.

References and Further Reading

6 Strange Facts about the Interstellar Visitor ‘Oumuamua – Scientific American Blog Network

Astronomer Avi Loeb Says Aliens Have Visited, and He’s Not Kidding – Scientific American






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