A plan to chase down our interstellar visitor 'Oumuamua

We have a plan to chase down our first known interstellar visitor

It came from outer space and its weird appearance and behaviour sent shockwaves around the world. Now, a group of astrophysicists are determined not to let the mysterious interstellar object ‘Oumuamua go gently into that good night.

“1I’Oumuamua” (pronounced oh MOO-uh MOO-uh) is the name assigned in October 2017 to the first confirmed interstellar object observed to enter our solar system. The 1I part of its name translates to Interstellar Object No. 1. ‘Oumuamua is a Hawaiian word meaning “messenger” or “advance scout”.

It appeared to be coming from the general direction of the star Vega, the brightest star in the constellation of Lyra.

Once in our solar system, it appeared to accelerate. And even changed course.

It’s on its way out again – after sparking intense fascination with its alien shape and behaviour.

It wasn’t a comet. It wasn’t an asteroid. At least, not as we know them.

Is it an alien spacecraft? Or is it an unexpected mix of already understood natural elements?

Flinders University space archaeologist Associate Professor Alice Gorman (aka Dr Space Junk) says the mysterious interstellar visitor still inspires fresh ideas seven years later.

““It could be just a very common rock – just not one we’ve categorised yet,” she says. “But it has opened up so many possibilities. It’s a puzzle.”

And unpicking that puzzle is producing further unexpected questions.

“A mission to this very strange object, Project Lyra, would seem an ideal way of answering all these questions,” says astronavigation software developer and Initiative for Interstellar Studies (I4IS) researcher Adam Hibberd.

And he’s shown it’s still possible. Despite ‘Oumuamua having left our Solar system.

Mothership of mysteries

‘Oumuamua appears to have been solid. It did not display the gas tail common to comets that fall towards the Sun from the outer edges of the Solar System.

It was reddish – generally interpreted as a sign of “weathering” of organic tholin molecules through exposure to cosmic radiation over hundreds of millions of years.

Its shape was also highly unusual.

Initially it seemed to be long and thin, like a cigar. But later analysis of the erratically pulsing light reflected from its 400m long surface suggests its form is closer to that of a pancake.

It was moving incredibly fast. Its Solar orbital escape velocity of 95,000 km/h translates to roughly 5.5 times the distance of the Earth to the Sun every year.

And ‘Oumuamua was accelerating.

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This artist’s illustration shows the wayward interstellar visitor ‘Oumuamua (pronounced oh-MOO-ah-MOO-ah) racing toward the outskirts of our solar system. The object, heated by the Sun (lower right), is venting gaseous material from its surface, as a comet would. Credit: NASA, ESA and Joseph Olmsted and Frank Summers

Was it an alien space probe? A discarded interstellar solar sail? A sticky, gelatinous blob? Or some strange comet-asteroid cross-breed we’ve never seen before?

A recent study published by the science journal Nature offers up one plausible interpretation: ‘Oumuamua has uneven deposits of frozen hydrogen on its surface. And its core is light enough to be pushed about when one of these boils off under exposure to sunlight.

“At first, everyone was hyped at how unusual it was,” says Gorman. “But it turns out there are at least seven other known objects that have exhibited this behaviour –  acceleration which doesn’t involve gravity. It just took an interstellar visitor for us to go back through our notes and discover all these other objects that really didn’t fit the categories we had squeezed them into”.

Whatever the reality, Gorman says ‘Oumuamua’s message to Earth is one of possibilities.

“The idea of turning an asteroid into a mobile habitation is a thing many science fiction authors have written about,” she says. “This shows propellant materials can exist naturally and – once combined with gravity curves – help cross interstellar distances”.

Interstellar tail chase

I4IS initiated “Project Lyra” – detailing plausible means of sending a space probe to observe ‘Oumuamua – a fortnight after it was discovered.

Seven years later, ‘Oumuamua is already far beyond the orbit of Neptune and passing through the distant icy objects of the Kuiper Belt.

I4IS hasn’t given up yet.

In a new blog published this month, Hibberd outlines how existing technology – including the Space X Falcon Heavy and NASA’s Space Launch System – can propel a probe towards Jupiter. The gas giant can then correct the probe’s inertia relative to ‘Oumuamua before falling back towards the Sun for a slingshot into a pursuit trajectory.

Hibberd’s latest scenario proposes a plunge to within 10 Solar Radii (about 700,000km) of the Sun’s surface – a distance already proven feasible with the success of the NASA Parker Solar Probe.

“Thus exactly the same heat shield technology (a Carbon-Carbon composite material) can be utilised,” Hibberd tweeted.

Curiosity (discovering the new) keeps us alive.

Adam Hibberd

At the point of closest approach – the periapsis point – a solid rocket booster can maximise the probe’s acceleration as it is slung away by the Sun’s gravity.

Launch opportunities to take advantage of suitable planetary alignments arise in 2030 and 2033. Once in motion, it would take a probe about 17 years to catch up with the rapidly receding interstellar object.


“Curiosity (discovering the new) keeps us alive,” Hibberd tweeted.

“After all it is only the unknown which can harm us; the known dangers we can find ways of evading or countering. This is the only pathway forward for humanity – onwards to expansion and discovery; we must always challenge ourselves.”

Spaceship Earth

‘Oumuamua has pierced the bubble of Earth’s isolation, says Gorman.

“It shows us that we’re much more a part of the galaxy than we’re used to thinking. Geographer Nigel Clark calls it a dynamic interchange with the cosmos.”

Humanity has already sent the Voyager and Pioneer probes outside our solar system. Now we know other things are passing through it.

We’re used to the metaphor of “spaceship Earth” as a little bubble floating about in the hostile terrain of our Solar system. But that idea can be extended to our Solar System as it moves through our galaxy. And our galaxy as it moves through the cosmos.

‘Oumuamua has pierced the bubble of Earth’s isolation.

Alice Gorman

“‘Oumuamua demonstrates so forcefully and clearly that, no, we aren’t’ sealed off from the rest of the galaxy,” she says. “We’re interacting with it all the time.”

And the evidence of this changing galactic environment is likely just waiting to be found.

“That movement happens over a scale of time that’s meaningless to us, but we can see the traces of it preserved on these airless worlds,” Gorman explains.

And ‘Oumuamua – with its believed cargo of water, hydrogen and tholins – reinforces the potential of a theory once derided as being “on the fringe”. Panspermia: The notion that the template for life can be “seeded” across the galaxy.

“Every time a mission is sent to a comet or an asteroid, these results always come back – bucket loads of water, hydrocarbons, prebiotic molecules, including those needed for DNA and RNA,” says Gorman. “This stuff is out there. Everywhere.”

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