The Science Behind Those Viral Oumuamua “Alien Spacecraft” Stories.

ʻOumuamua, the first interstellar object to be detected passing through our solar system, does not have to be an alien spacecraft to be cool.

If you’re a scientist who wants to indulge in a bit of speculation, or if you’re a journalist looking for a sensational claim to attribute to a scientist, it’s best to focus on the paragraph that applies. the end of ‘a scientific article’. This is where scientists often question their ideas, offer alternative hypotheses, or suggest future research before restating the clearest summary of the study’s findings.

Unfortunately, presenting this part of the research in headline form – while great for clicks – rarely sheds light on the actual scientific debate and often confuses the actual information being reported. presented article.

A prime example of this phenomenon made headlines in early November 2018 with headlines like “Mysterious interstellar object floating in space could be alien, researchers say Harvard said” from USA Today:

It’s been dubbed a comet, an asteroid, and a new class of interstellar object. Now, a paper from Harvard astronomers suggests one more possibility into the mysterious object nicknamed “Oumuamua”: Alien probe.

It is true that a manuscript of a study was posted online on November 1, 2018 (to be published in the Astrophysical Journal) and was written by two Harvard astronomers, Professor Shmuel Bialy and the department head Avi Loeb, proposed the possibility of a recently observed interstellar connection. The object originally named ‘Oumuamua may actually be a device created by an extraterrestrial civilization. (The character before “Oumuamua” is a Hawaiian sign called ʻokina, which represents a glottal stop sound.)

Their paper tested the plausibility that the object’s apparent acceleration could be explained if the object was a thin pancake-shaped plate pushed by the force of solar radiation. Their speculations about why such a shape could exist have made headlines. “A more exotic scenario is that ‘Oumuamua could be a fully operational probe intentionally sent close to Earth by an extraterrestrial civilization,” the authors add near the end of the paper. The myopic focus on this single phrase, while perhaps good for clicks, provides an incomplete view of what is itself a fascinating scientific mystery.

What is ‘Oumuamua’ ?


On October 19, 2017, a ground-based telescope in Hawaii called PAN-STARRS detected a fast-moving object about a quarter of a mile in diameter with an extremely unusual orbit. In a paper published in the journal Nature titled “A Brief Visit to a Red, Extremely Long Interstellar Asteroid,” a team of researchers concluded that the object is a Interstellar object detected passing through our solar system – for the first time:

Designated as 1I/2017 U1, this object is clearly from outside our solar system, and as such is the first detected interstellar object. Given its discovery and follow-up observations from multiple Hawai‘i observatories, 1I/2017 U1 has been named ‘Oumuamua, which in Hawaiian reflects the way this object is like a scout or messenger sent from the distant past to reach out to us.

“Oumuamua, which moves too fast to be attracted to our solar system, has a dark red surface “consistent with the organic-rich surface of a comet” and tumbles and/or spins rapidly.

Image Via NASA-JPL

What About ‘Oumuamua Were The Harvard Researchers Investigating?

On June 27, 2018, a team of researchers published another paper in Nature about ‘Oumuamua, which explored the observation that ‘Oumuamua is accelerated by a force other than the gravitational attraction of nearby objects, suggesting that this may be the result of a cometary force. degassing:

We report the detection … of non-gravitational acceleration in the motion of ‘Oumuamua … After ruling out solar-radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object, and geometric effects…, we find comet-like outgassing to be a physically viable explanation, provided that ‘Oumuamua has thermal properties similar to comets.

Many researchers, including the authors of the attention-grabbing study, find the comet propulsion explanation insufficient, because observations show the object was not a comet and may be more accurately described as an asteroid. “Despite its close approach to the sun,” the authors write, “Oumuamua shows no signs of cometary activity, no comet tail or gas emission/absorption lines.”

In their paper, Bialy and Loeb presented an alternative hypothesis to explain comet propulsion:
“The possibility that ‘Oumuamua is a thin object accelerated by the pressure of solar radiation, which would naturally lead to excessive acceleration.”

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