NASA studying weird cigar-shaped asteroid

It came from an unexpected detection.

It wasn’t seen until after it had swung close past the Sun.

It’s once again headed out into deep space.

NASA has published a new study stating that, when it pointed its infra-red Spitzer Space Telescope towards Oumuamua in November last year, it saw … nothing.

Which is, in itself, telling.

“Oumuamua was too faint for Spitzer to detect when it looked more than two months after the object’s closest approach to Earth in early September,” NASA says. “However, the “non-detection” puts a new limit on how large the strange object can be.”

It also indicates Oumuama was unusually bright.

When Oumuamua was first seen plunging past the Sun, it did not appear to have a tail — as comets do — caused by ice boiling off into space.

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But, since then, the interstellar object has been noted to change course a little — and accelerate a little – like comets do, under the thrust of ice warmed by sunlight into ejected gas.

Is it an alien space probe, as one Harvard academic (himself a proponent of sending probes to nearby Proxima) suggests?

Or is it something else — a weird concoction of interstellar substances unlike anything we’ve ever seen?

SHINING A NEW LIGHT

The new study now suggests that ‘Oumuamua may be up to 10 times more reflective than omets normally found in our solar system.

That is surprising.

“Oumuamua had been travelling through interstellar space for millions of years, far from any star that could refresh its surface,” the NASA report states. “But it may have had its surface refreshed through such ‘outgbading’ when it made an extremely close approach to our Sun, a little more than five weeks before it was discovered.”

Such ‘outgbading’ would have blasted away and grit on Oumuamua’s surface, and potentially allowed fresh deposits of highly reflective ice to harden in its place.

And this brightness may have caused Oumuama to look bigger than it actually was to optical telescopes, such as Hubble.

NASA now thinks it is less than half the original estimates of its size, and is instead somewhere between 400m and 100m long.

“Usually, if we get a measurement from a comet that’s kind of weird, we go back and measure it again until we understand what we’re seeing,” said NASA’s Davide Farnocchia. “But this one is gone forever; we probably know as much about it as we’re ever going to know.”

NASA concludes that the jets of gas from vents in the surface of ‘Oumuamua have given it a slight boost in speed, as suggested earlier this year.

The Spitzer Space Telescope observations — despite not seeing ‘Oumuamua — reveals it must be small enough for such acceleration to take place.

“That determination was dependent on ‘Oumuamua being relatively smaller than typical solar system comets,” NASA states.

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‘Oumuamua was first detected by the University of Hawaii’s Pan-STARRS 1 telescope on Haleakala, Hawaii, in October last year. Its name is a Hawaiian word meaning “visitor from afar arriving first”.

Hubble had a look. So did several ground-based telescopes. They saw it was reflecting sunlight — but that it was varying dramatically. This suggested Oumuamua was elongated, and less than 800m long.

TO BE, OR NOT TO BE?

It does nothing to confirm — or deny — recent controversial claims by two Harvard professors, Shmuel Bialy and Abraham Loeb.

“A more exotic scenario is that ‘Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilisation,” they wrote.

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But this was pure speculation, based solely on the object’s unusual 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.

And the smaller size calculated by the Spitzer observation is also an argument space probe proponents will dismiss: the Harvard professors are themselves advocating ‘star chips’ — tiny solar-sail propelled probes — be launched at nearby stars.

But NASA’s observations also make it more likely that Oumuamua was a dirty interstellar comet, crusted by the deposits of thousands of years 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.

We’ll never know for certain, though.

There is no way to get a good look at the rapidly retreating enigma.