IT WAS our first known interstellar visitor when it was discovered flashing past the Sun in October last year. Dubbed 'Oumuamua' – Hawaiian for messenger – it's been determined to be this solar system.
Its trajectory had been traced. And the track it could not possibly have been at orbit around our Sun.
Follow-up observations after the Pan-STAARS-1 telescope in Hawaii announced its discovery
It was elongated. It was about a kilometer long. It was a strange reddish color.
Naturally enough, some speculated it could be on alien spacecraft. SETI (the Search for Extraterrestrial Intelligence)
It found nothing. There were no observable omissions from the tumbling interstellar visitor.
And, as Oumuamua was moving so fast as it was already in the outer reaches of our solar system, interest waned.
There just was not much more we
now, a new study by Harvard Smithsonian Center for Astrophysics astronomers has postulated that it may, after all, have been put on alien object.
A light sail.
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The study titled Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration, presented by Shmuel Bialy and Professor Abraham Loeb.
Professor Loeb is a committee member of the Breakthrough Starshot committee ̵
Any examination of the u nusual nature of Oumuamua must include the possibility that it might be a lightsail of artificial origin, "he writes
Oumuamua was found to have a high density , Normally, this would indicate that it is made of rock and metal.
But a spectral analysis – where light is broken down into its components to identify the chemicals influencing its colors – indicated it was much more than expected.
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The big eyebrow raiser was Oumuamua's speed.
After passing the Sun, it actually sped up …
Unless it's a comet, venting from the warm face closest to the Sun.
So what, where's that comet-like tail?
The Harvard astronomers also Oumuamua's spin.
With these anomalies, Bialy and Loeb suggest that there is only one other alternative: that it is a
"The first artificial relic has been exposed to the first interstellar object in the solar system, 'Oumuamua, "Professor Loeb writes.
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It's a concept to break through starshot is working on.
It wants to sent 'sparkips' – tiny solar-sail powered sensors – to Proxima B.
"We explain the excess acceleration of 'Oumuamua away from the Sun as the result of the Sunlight exerts on its surface," they write. "For this force to explain excess acceleration, the object needs to be extremely thin, or order a fraction of a millimeter in thickness but not in size. This makes the object lightweight for its surface area and allows it to act as a light sail. Its origin could either be natural (in the interstellar medium or proto-planetary disks) or artificial. "
The Harvard astronomers attempted to compute the probable shape, size and mass of any interstellar light-sail would need.
It would require the intense cold and extreme radiation of deep space.
Their state of affairs could not be bettered by an incredibly thin – just a fraction of a millimeter – thick sheet of metal.
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"For a thin sheet of this requires a width of ≈ 0.3-0.9 mm," the study reads. "We find that extremely thin, search for object would survive on interstellar travel over Galactic distances of about 5 kpc, withstanding collisions with gas and dust-grains as well as from rotation and tidal forces."
Professor Loeb states similar Lightsails have already been designed and built here – IKAROS and his own Starshot Initiative.
Bialy and Loeb speculate it could be flotsam – a jetissoned solar sail floating at the whim of the interstellar winds.
"This opportunity establishes a potential foundation for a new frontier of space archeology, namely the study of relics from past civilizations into space," Loeb recently wrote in Scientific American .
"Finding evidence for space junk of artificial origin would provide an affirmative answer to the age-old question" Are we alone? "This would be a dramatic impact on our culture and add a new cosmic perspective to the significance of human activity. "
Equally, Loeb said, Oumuamua could be a space probe.
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" The alternative is to imagine that `Oumuamua was on a reconnaissance mission, 'he told Universe Today. He said the objects path was simply too convenient.
It was within 0.25 AU (Astronomical Units, the distance of the Earth from the Sun). It's just about 0.15AU of Earth.
Both astronomers concede we just know too little about Oumuamua to reliably guess its nature. But, at the very least, it has to be the characteristics of an individual or object.