LAST week, astronomers the world over began pouring over some strange results that have been sent back by the Kepler Space Telescope. It’s a NASA satellite tasked with the role of finding planets orbiting distant stars. It’s looked at more than 150,000 so far.

This time it’s found something unexpected.

We don’t know what, yet. But the implications are astounding.

Put simply, something really strange is happening around the star KIC 8462852. Where a planet the size of Jupiter blocks barely 1 per cent of a star’s light, something is managing to shade us from this one by up to 22 per cent. Unlike a planet, it’s orbit is irregular — and it appears to be changing in shape and size.

That’s not normal.

But it is a trace alien hunters such as SETI have been seeking for decades: It’s a potential sign of a hypothetical form of advanced space-faring civilisation.

It’s called a Dyson sphere — a colossal solar array built in space designed to catch as much of the star’s energy as possible.

It’s a compelling possibility.

But there are alternate — though equally unproven — explanations. And signs are already beginning to emerge that one in particular may end up being true.

The star — and whatever planets may orbit it — may be in the midst of being pounded by a titanic influx of cometary debris, kicked up from the outer reaches of the solar system by a cosmic near-miss. A close brush with a wayward star.

If so, it’s an event that may have implications for us — in about 240,000 years time. We’ve found just such a ‘death star’ headed our way.

HERE BE ALIENS?

The Kepler Space Telescope detects new planets orbiting their host suns by measuring and timing, minuscule fluctuations in a star’s brightness.

But in this case the fluctuation in the star’s light isn’t so tiny. Nor is it regular.

There’s definitely something odd about KIC 8462852.

At first it was just one set of signals among many. But it drew the attention of a group of amateur enthusiasts working for the Planet Hunters project.

What they found was odd enough for the Kepler team to go back to basics and check the functionality of their telescope and the algorithms which interpret its digital data. Is some glitch producing a spoof signal?

Everything checks out okay.

KIC 8462852 an F-type star, meaning it is hot and yellow in colour with a mass perhaps a little heavier than our own. It sits some 1480 light years away in the constellation of Cygnus.

But Kepler has recorded fluctuation in the star’s light for periods of between five and 80 days at a time.

That rules out an enormous, orbiting planet.

It must be something irregular, with a strange orientation.

Could it be the patchy remnants of a huge ring of rocks and ice — the stuff that becomes planets?

Some astronomers think not. KIC 8462852 is not a young star. It’s had plenty of time to sweep up its inner solar system. Besides, such an asteroid cloud also would emit infra-red radiation that Kepler could detect. Such a glow has not yet been seen.

Therefore aliens?

“It is the most interesting singular object from a SETI perspective that we know about today,” said Andrew Siemion, director of the University of California’s Berkeley SETI Research Center.

He says that the idea the star’s light is being blocked by enormous pieces of alien architecture is — at this stage — just as likely an explanation as any other.

It’s an idea fresh in his mind. He’d only just finished addressing the US Congress on SETI’s expectations for the next few years.

“Technologies far more advanced than our own could potentially produce even more dramatic evidence of their presence,” he told an assembly of politicians late last month. “Large stellar-scale structures could cause apparent modulation in starlight as they orbited their host, and massive energy usage by a super advanced civilisation might be revealed by its thermodynamic signature, even from millions of light years away.”

IS IT A DYSON SPHERE ...

Physicist Freeman Dyson famously suggested that as civilisations become increasingly hungry for energy, they’d eventually attempt to harvest the entire output of their home star.

One way to do this would be to sheath the boiling cauldron of nuclear fission in a sphere of solar panels.

This gave rise to the idea of seeking such solar-system encompassing megastructures as an indication of advanced alien civilisations.

“The astronomical literature is rife with speculation that very advanced intelligences may produce signatures detectable by traditional astronomical observations,” SETI’s Andrew Siemion says. “Massive Dyson structures … might be built to harvest the energy of Suns and could be detected in the latest generation of infra-red sky surveys.”

That’s an enormous amount of energy: In the case of our own Sun, such a sphere would power several trillion Earths. But, then, interstellar travel may need energy on such a scale.

But such structures have other uses:

“A very advanced civilisation using a naturally bright astronomical source as a pseudo-artificial beacon, such as modulation of a naturally expanding and contracting star or interference with a pulsar, could be discovered through careful analysis of variable star or pulsar observations,” Siemion says

Is KIC 8462852 either of these?

Extraordinary claims require extraordinary evidence

In this case, there are plenty more probable natural alternatives that would need to be ruled out.

… OR INTERSTELLAR BILLIARDS?

In the case of KIC 8462852, there is an elephant lurking in the room.

A nearby wandering star.

The telemetry hasn’t been done yet: This is one of the reasons why more telescopes will soon be peering in that general direction.

But it seems a nearby star may have had a recent close encounter with KIC 8462852, stirring up an immense cloud of ice and debris from the outer reaches of the solar system- the Oort Cloud — in its wake.

Postdoctoral researcher Tabetha Boyajian of Yale University, part of the Planet Hunters team, has published a paper supporting this argument.

Such a wanderer could potentially cause this delicately balanced cloud of comets to clump up and tumble down the gravity well of its parent star.

The odds of observing such an event happening in such a narrow, 100,000 thousand year or so window are astronomical. Though not as extreme as finding aliens.

Such clumps could explain the star’s unusual, irregular dimming.

Whatever planets the star may have had, however, would now be facing an intense barrage of comet impacts. Most of the debris, however, would be evaporating as it falls into KIC 8462852’s hot embrace.

But Penn State astronomer Jason Wright told Popular Science this idea doesn’t gel with him. He working on publishing his own paper arguing the Dyson sphere case.

“It’s hard to imagine how comets could block that much light — you need a huge number of them, and we must have caught them at a time when they happened to be all clumped together.”

But he concedes aliens are a long shot.

“Aliens should always be the very last hypothesis you consider,” Wright told The Atlantic, “but this looked like something you would expect an alien civilisation to build.”

THE SEARCH IS ON

SETI is just one of several organisations keen to take a closer look at KIC 8462852. The alien hunters hope to use some of the $100 million donated to the organisation earlier this year by Russian billionaire Yuri Milner for such a quest.

They have already pointed the Allen Telescope Array in California towards it. They hope that breaking down the spectrum of 9 billion radio channels coming at us will reveal more about what’s going on in orbit about at KIC 8462852.

They’ve also applied for time on the 100 metre National Radio Astronomy Observatory at Green Bank in West Virginia to point it at the erratic enigma.

“We’ll look at each channel relative to the others,” says SETI’s Andrew Siemion, “and see if there’s a lot of energy at just one frequency.”

He’s looking for a narrowband radio transmission. No known natural phenomenon produces such a signal.

But they are just one group of researchers among many vying for the radio telescope’s time. They won’t know until next year if their application has passed the stringent — and competitive — criteria.

There are other ways to sift out more information about what may be causing the star’s strange fluctuations.

The variations in the star’s light can be broken into spectra. The differences in light as it changes intensity may help reveal what the shadowy object is made from.

ONCE WERE ALIENS

Such strange and tantalising traces from space have fired up speculation about aliens before.

The most notable was the discovery of Pulsars in 1961.

The new technology of radio telescopes was behind this one. Someone was taking a tentative first peek at the black holes at the heart of distant galaxies. What they saw set off alarms bells.

A regular, pulsing, radio signal — shining like a beacon in space.

Exactly what you’d expect from aliens attempting to draw attention to themselves.

The signal was designated LGM-1: That’s “Little Green Men ” number one.

But soon the telescope was pointed at other galaxies: And found the same thing.

Then again. And again.

Soon it was obvious that, instead of being surrounded by thousands of civilisations, a new natural phenomenon had been discovered.

The pulsar. These are rapidly spinning neutron stars which have such intense magnetic fields they concentrate much of the star’s radiation into searchlight-like beams.

Not aliens.

A similar surge of excitement was recently experienced in Australia. This time the cause ended up being much more mundane.

The Parkes radio telescope in New South Wales began noticing unnatural, ultra-short radio bursts appearing in their feeds.

Closer analysis revealed the signal didn’t seem to come from any point in space, nor were other observatories reporting the strange transmissions.

So conditions weren’t quite right to call out aliens.

It took more than 15 years — and an observant student — to discover that the source of the signals was staff opening their kitchen’s microwave oven before it had fully finished.

Nevertheless, the odds for such a discovery being real are improving.

Telescopes such as Kepler have found almost 2000 exoplanets — planets orbiting other stars — in just the past few decades. This means the galaxy must be filled with billions of them.

The chances of life being out there — even intelligence — is therefore a matter of doing the maths.

@JamieSeidel