"The bizarre space object Oumuamua has scientists completely baffled. It’s possible we may have just missed first contact with aliens."
"It may be an asteroid. It could be a comet. Perhaps it is … something else. But ever since humanity spotted it last year, I/2017 U1 ‘Oumuamua — the elongated chunk of something shiny spinning through our Solar System — has managed to give us the slip. 'Oumuamua means “scout” or “messenger” from the past, in Hawaiian. It may be a very appropriate name. There’s reason to suspect it could have an alien origin.
It’s behaving weirdly: flying through our Solar System on an open-ended parabola, proving it must have come from deep interstellar space. Its eerie red hue is shinier than a typical comet. It’s accelerating: admittedly by only a tiny amount, but something is giving 'Oumuamua a push. It could be comet-like ‘outgassing’. But at no point has the mysterious object been seen to have a comet’s tail.
It has a weird shape. Based on its erratic flashing, astronomers have inferred 'Oumuamua must be long and thin. Few known asteroids and comets are like that. But … for it to be an alien artefact would be extraordinary. And to prove that would require some extraordinary evidence. However, our chances of learning anything more from our first known interstellar visitor are very slim. It’s racing away — back into deep space — at some 95,000km/h. There are, however, other possible — and more probable — alternatives..."
"The Spitzer Space Telescope — despite not seeing 'Oumuamua — reveals it is small enough for such acceleration to take place. “That determination was dependent on 'Oumuamua being relatively smaller than typical solar system comets,”..
"After crunching the probabilities, the researchers found that there should be at least 66 other interstellar objects, ranging in diameter from roughly 100 meters to 10 kilometres in size, captured in the Sun’s gravitational well. “We find that there should be hundreds of 'Oumuamua-size interstellar objects identifiable by Centaur-like orbits,” the study reports. A Centaur a small body that orbits the Sun between Jupiter and Neptune, but cuts across the path of one or more of the giant planets.
"“A more exotic scenario is that 'Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilisation,”... But this was pure speculation, based solely on the object’s surprising speed and course. That it was so reflective could, however, add fuel to the ‘alien space probe’ idea. Light sails work in a similar way wind sails do — harnessing the energy of solar winds by reflecting them in another direction to generate thrust.
"“No scientist has claimed 'Oumuamua is alien in this discussion — they have just raised questions and explored answers. There is no point in shying away from a proper discussion on the search for extraterrestrial intelligence, or in being personally critical of colleagues … If aliens are claimed, direct and robust evidence is required — not a conclusion based on a few observations that are difficult to explain, plus a bunch of assumptions.”
What has been seen makes it most likely that 'Oumuamua is, in fact, a dirty interstellar comet, crusted by deposits and turned red by thousands of years of exposure to cosmic rays in interstellar space. Once close enough to the Sun to boil this away, the shiny inner core was exposed — changing its characteristics in such a way as to alter its orbit."