So far we have observed 1858 planets orbiting other suns. There are 4661 more suspects awaiting confirmation.

What solar systems we’ve seen so far has been making our astronomers nervous.

They’re not much like ours.

Among the differences is one very (very) big one: Where their “Jupiters” are.

It’s something that may have hefty implications for the chances of finding life.

But an international group of astronomer’s have just had a “Eureka” moment: They’ve found the first distant solar system that may be somewhat like our own.

HIP 11915 has a Jupiter-sized planet orbiting at a Jupiter-like distance from its Sun-like star.

“What makes this new discovery so exciting is that the giant gravitationally ‘bully’ is far from where potential habitable worlds may lie,” says Swinburne astrophysicist Dr Alan Duffy. “Instead it’s gravity will hoover up small asteroids and just like our Jupiter will protect the inner rocky worlds if they exist.”

It may also be a vital element in the formation of life-friendly planets.

Bucking the trend

According to observations made in the past two decades, the two “average” solar system types appear to go something like this:

It has a few “super-Earths”: Enormous rocky worlds up to 10 times bigger than our own with dense atmospheres and orbiting closer to their stars than Mercury does to ours.

EARTH 2.0: Inside the search for habitable planets

It has one or two ‘hot-Jupiters’: About 10 per cent of surveyed solar systems have gas giants swinging about their stars in very close orbits. Unlike our chilled Jupiter and Saturn, these worlds are raging infernos.

“The standard issue planetary system in our galaxy seems to be a set of super-Earths with alarmingly short orbital periods. Our solar system is looking increasingly like an oddball,” a study released earlier this year reads.

If so, we’ve just found our eccentric twin.

But it also may be largely a result of observational bias. It’s been much easier to find large planets in fast orbits.

Either way, an ESO statement released last week suggests the discovery of a solar system with a “Jupiter” orbiting quietly at a middling distance from its star “opens the possibility that the system of planets may be similar to our own”.

“Finding a Jupiter twin is an important milestone on the road to finding a planetary system that mirrors our own,” the release reads.

So what so odd about ours?

Recent computer simulations suggest Jupiter may have been something of a wayward youth.

Wandering Jupiter

It’s been argued the king of planets cut loose in the formative years of our solar system some 4.5 billion years ago, barrelling through the inner worlds like an exuberant toddler.

The embryonic planets already in that space — still emerging out of the clouds of gas and dust swirling around our young Sun — would have been tumbling into chaotic orbits. Collisions created huge debris clouds which, in turn, smashed into other developing planets.

“During the formation of the Solar System, the outer-most planets definitely wandered a lot - that’s how Pluto got caught in its peculiar dance with Neptune,” Says Monash University astrophysicist Michael Brown. “Jupiter wander a bit wouldn’t be a surprising in that context.”

Eventually, as it matured, Jupiter settled into its current orbit — probably put in its place by the other big kid on the block, Saturn.

The first generation inner-planets probably spiralled into the Sun, the report says.

This new found peace allowing what debris and gas Jupiter left behind to coalesce into the rocky orbs we know as Mercury, Venus, Earth and Mars.

But, given the way Jupiter had swept out the inner solar system, these latecomers didn’t grow as large — with as thick an atmosphere or as close to the Sun — as it now seems other solar systems do.

Jupiter has since turned altruist, defending the inner solar system from wayward asteroids and comets with its strategically-placed gravitational influence.

It’s by no means the only explanation for our solar system’s early years: But the paper titled “Jupiter’s decisive role in the inner Solar System’s early evolution,” published in March in the journal, Proceedings of the National Academy of Sciences, dovetails nicely with the new discovery.

“There is a lot of evidence that supports the idea of Jupiter’s inward and then outward migration. Our work looks at the consequences of that. Jupiter’s ‘Grand Tack’ may well have been a ‘Grand Attack’ on the original inner solar system.” study co-author Gregory Laughlin says.

But it’s an attack that may have established the building blocks for life.

HIP and happening

The ESO 3.6-metre telescope in Chile made the find announced yesterday. The team had been purposely targeting Sun-like stars to find a solar system like our own.

They found what they were looking for.

Equally important to the position of the gas giant is its star’s chemical composition: It is very similar to that of ours — teasing the possibility that there may also be rocky planets in its orbit.

“This discovery is, in every respect, an exciting sign that other solar systems may be out there waiting to be discovered,” study lead author Megan Bedell says.

There are other candidates for a Jupiter “twin”, HD 154345. But its star has been classified as metal poor. Then there’s HD114613 which was found by Australian scientists a few years back: It was found to have an eccentric orbit.

“Astronomers have previously found solar systems that are a bit like ours,” says Dr Brown. “For example, with rocky planets in the goldilocks zone (not too hot, not too cold) surrounding their stars, but Jupiter analogs are few and far between.”

Despite the apparently high odds, chances are we may soon see a lot more “Jupiter” solar systems.

“To be sure that the wobble we’re seeing in the motion of a star, pulled by the planet as it goes around it, is real we have to watch it make a full orbit (at least),” Dr Duffy says. “Since this Jupiter, like our own, takes a decade or so to go around the star, it means finding these worlds takes 10 or more years. I expect we’ll find more Jupiter-twins soon.”

The prospects are enticing.

“The quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavours in astronomy,” Jorge Melendez of the University of de Sao Paulo, Brazil, says.

Life force

We’ve observed 100 billion galaxies, each with 100 billion stars. In the past two decades, we have discovered most of those stars have at least one world. From what we know about the resilience of life and the conditions in our own solar system, there should probably be trillions of habitable planets out there.

So why have we not seen a single hint of extraterrestrial civilisations?

Where is everybody?

It’s called the Fermi Paradox.

Perhaps our unusually small inner worlds may have much to do with it.

“As we don’t know exactly what makes our solar system unique in hosting life we are left trying to find other star systems that are as identical to ours in every way to maximise the chance of discovering habitable worlds,” Dr Duffy says. “Finding a sun-like star with a Jupiter-like worlds in the right place is huge first step.”

Our worlds are mellow. It seems typical solar systems are not.

“One of the predictions of our theory is that truly Earth-like planets, with solid surfaces and modest atmospheric pressures, are rare,” Laughlin said.

The chances of other solar systems forming with a wayward Jupiter and a disciplining Saturn appear to be somewhat slim.

Instead they may be filled with first generation planets, formed when their inner solar systems were still rich in gas such as hydrogen.

As a result, they could be filled with super-Venuses: Big. Hot. Dense.

If life was to evolve in these challenging conditions, it would need to be very different to our own.

@JamieSeidel