A small icy world found to be travelling backwards on a strange orbital plane has scientists wondering what is going on far out in the solar system.

But that’s not the only space mystery this month.

A new study has only added to questions about a star around 1500 light years away that has strange, inexplicable dips in brightness. That weird behaviour gave rise last year to the fanciful notion it may be surrounded by some sort of ancient megastructure.Kiwi Dr Michele Bannister, an astronomer at Queens University in Belfast, alerted the world to its strangeness with a series of tweets last week.

“I hope everyone has buckled their seatbelts because the outer solar system just got a lot weirder,” Bannister said.

The object of all the excitement is a small icy world, possibly less than 200km in diameter, beyond Neptune – therefore known as a trans-Neptunian object – and 160,000 times fainter than the distant planet.

It has been nicknamed Niku, after the Chinese adjective for rebellious. That’s because compared to most other objects in the solar system it is going backwards and it’s orbiting on a plane tilted at 110 degrees from the plane of the solar system on which the planets lie.

According to Astronomy magazine, many smaller objects can be in inclined orbits, but Niku is one of the largest objects in such an orbit.

Wired said the area of the solar system called the Kuiper Belt, which stretches for billions of kilometres beyond Neptune, has provided a host of mysteries to solve during the past few years.

During just the past few months, countless new icy objects had been found in the far reaches of the solar system, and Niku wasn’t the only one with weird orbits that were difficult to explain, it said.

One of the biggest mysteries was speculation about the existence of the so-called Planet Nine, somewhere out on the edge of the solar system.

Caltech astronomers Professor Konstantin Batygin and Professor Mike Brown predicted the existence of such a planet, saying it would explain the strange clumping behaviour of a group of dwarf planets in the Kuiper Belt.

Some scientists had considered Planet Nine could have something to do with the strange orbit of Niku, but they found it and its associated planetoids were too close to the rest of the solar system to have potentially been tugged out of place by such a planet.

As New Scientist explained it, anything that doesn’t orbit within the plane of the solar system or spins in the opposite direction must have been knocked off course by something else.

So if Planet Nine didn’t explain the strange orbit of Niku and other apparently related objects, something else must.

“We don’t know the answer,” Matthew Holman, from the Harvard-Smithsonian Centre for Astrophysics, part of the team that discovered Niku, said.

Meanwhile, continued observations of star KIC 8462852 have only added to its mystery. Known as Tabby’s Star – after Tabetha Boyajian, then a postdoc at Yale University, who announced the discovery of this system”s strange patterns of brightness – it is somewhat similar to our Sun.

One theory to explain the star’s weird dips in brightness was that it was being partly obscured by a comet swarm that was in the process of breaking up. But the most exciting possibility floated was that megastructures had been put in place around the star by an extraterrestrial intelligence.

To try to solve the puzzle some researchers turned to historical archives. More than 1200 images revealed that Tabby’s star gradually dimmed by as much as 15 per cent over the course of a century, New Scientist reported.

Other data came from Nasa’s Kepler space telescope, which continually monitored the star – and 100,000 others – from 2009-2013.

Researchers found that for the first 1000 days of the Kepler mission, Tabby’s Star decreased in brightness at roughly 0.34 per cent a year. Over the next 200 days, the star’s brightness dropped another 2.5 per cent before beginning to level out. It was a much more rapid change than before.

That means the star undergoes three types of dimming: the deep dips that first made it famous, a relatively slow decline, and the intermediate rapid decline that occurred over a few hundred days, New Scientist said.

“We can come up with scenarios that explain one or maybe two of these, but there’s nothing that nicely explains all three,” Benjamin Montet from the California Institute of Technology – one of those who looked at the Kepler data, said.

Canterbury University senior lecturer in astronomy Michael Albrow, who is involved in the search for planets outside out solar system, said he expected there would be some natural explanation for the star’s varying brightness.

“I doubt it’s an alien megastructure,” he said.

It must be caused by some things in front of the star and there were a range of possibilities as to what those could be.

Probably most astronomers though that because there was life on Earth, there was no reason there wasn’t life elsewhere, Albrow said.

“Whether we will actually detect evidence of it is another matter.”

One of the reasons astronomers were looking for planets around other stars was to try to find evidence of life elsewhere in the galaxy, Albrow said.

“Planets are quite hard to find … We know about a few thousand planets now that orbit other stars, mostly around stars fairly close to our Sun on a galactic scale.”

[Source: Stuff]