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Manchester

Space Rock Fly-By Still Making Headlines

Voice of America
09 Nov 2018, 02:05 GMT+10

WASHINGTON - Readers with a science bent have likely seen at least one headline about a research paper proposing that the mysterious little space rock with a really funny name that zoomed between the Sun and Mercury last year might have alien origins.

The research paper is from Harvard University, the Ivy'est of Ivy League schools. The Harvard Smithsonian Center for Astrophysics, to be exact.

So could it be that the object, called Oumuamua, Hawaiian for 'scout', is truly some kind of alien artifact, or an actual space probe sent to spy on all us Earthlings?

Hate to be a bummer, but no!

Let's throw away our scientific and journalist objectivity for a moment and admit that most people want the answer to be 'yes.'

That's why scientists spend so much time looking for extrasolar planets that are like Earth, and why we want to get closer looks at Mars, and send probes to Europa or Enceladus or any place with oceans of liquid water. Researchers and astronomers all want some proof that humans are not all alone in the universe.

But in this case, based on conversations VOA has had with astronomers, and based on everything scientists know about space rocks, comets, and asteroids, Oumuamua doesn't seem to be acting much differently than any other space rock out there in the void.

But here's what scisntists do know about Oumuamua, and that might help explain why some scientists are so excited about it, whether it offers proof of alien intelligence or not.

Oumuamua was the first interstellar object to visit our solar system. That means it came from another star system like our own. It flew between Mercury and the Sun in November 2017, almost exactly a year ago.

It moved really quickly, at about 136-thousand kilometers per hour. Michele Bannister from Queen's College in Belfast told VOA that scientists only had about three weeks to get a good look at it.

Credit: NASA

Oumuamua is reddish, and about 400 meters long. However, it's 10 times longer than it is wide, so basically it looks a bit like a giant, dirty interstellar icicle. In space terms, 400 meters is tiny, so just finding the thing was a big win for astronomers.

"For decades we've theorized that such interstellar objects are out there,' says NASA's Thomas Zurbuchen 'and now―for the first time―we have direct evidence they exist."

That's really interesting, but how did the whole 'aliens' thing get started? Well, it turns out that Oumuamua is definitely 'unusual' in that it isn't just ambling through the galaxy. It's changing speed and direction by itself. Bannister calls this 'non-gravitational acceleration.'

It turns out that's not particularly strange or even unusual. Bannister says this rock is likely filled with the kinds of things that comets and asteroids generally have in abundance. Carbon monoxide, for instance or cyanide. If so, when they get close to the sun and get warm, these gases shoot out like jets in a process called sublimation. This is likely what made Oumuamua look like it was acting under its own power, because it was in a way.

Here's how NASA explains this outgassing acceleration:

Credit: NASA

We'll never really know

But that perfectly reasonable explanation didn't stop Harvard scientists Shmuel Bialy and Abraham Loeb from putting forth a few possible alternate possibilities for Oumuamua, including one that suggests our interstellar space rock was a lightsail, a giant sail that uses energy from the sun instead of wind to push a vehicle through space.

They suggest this might be a possibility because some other studies suggest our interstellar wanderer isn't a comet and isn't doing any outgassing. Hence the solar sail idea. And the team does the math to show how Oumuamua might fit the bill.

The other possibility put forward by Bialy and Loeb is that 'Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization.' They do the math here as well to show how Oumuamua's trajectory might make sense if it was aimed our way.

It's important to note that the paper hasn't been peer reviewed yet, which is the process all scientific research goes through before it gets published by reputable journals like Science, or Nature. That means other scientists in the same field read it over, give input and check on its validity. So we'll see what happens with this paper.

But as far as Oumuamua goes, it's too small for even our best telescopes to get a look at, so researchers have all the information they'll ever have.

But don't worry, there are likely a lot more Oumuamua's out there. "The galaxy is filled with flying rocks," Bannister says. 'Trillions upon trillions' of space rocks, ranging in size from a 'skyscraper' to a planet, are likely roaming around the galaxy. And if we're lucky, Bannister says we should be able to see about one a year.

So, in a way the Earth is getting visitors from other stars, but they're just random rocks passing through. So, no aliens, but still pretty really great science.

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