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Our solar system had a close encounter with another star 70,000 years ago, new research has revealed.

The recently discovered star passed just 0.8 light years away from our own sun and was so close it passed through the icy cloud of outer comets that encircles our solar system.

This makes it the closest a star has come to our solar system - five times nearer than Proxima Centauri, our current closest stellar neighbour.

Scholz star, shown in the artists impression above as behind its brown dwarf companion in the foreground, passed within 0.8 light years of the Sun (shown as the bright star on the left) around 70,000 years ago

Since that encounter, the star, which is known as Scholz's star, has moved off at high speed and is now thought to be around 20 light years away.

Astronomers discovered the star's flyby by tracing its movement through the sky and found it would have passed within the outer Oort Cloud of comets.

Dr Eric Mamajek, an astronomer at the University of Rochester who led the study, said that it is unlikely the star would have caused much disturbance to the scattered icy comets that orbit the outermost reaches of our solar system.

However, he said it raised the possiblity that other close encounters with stars in the future could have a far greater impact.

He said: 'Using the best available astrometry, our simulations suggest that the probability that the star penetrated the outer Oort Cloud is ∼98%.

'While the flyby of this system likely caused negligible impact on the flux of longperiod comets, the recent discovery of this binary highlights that dynamically important Oort Cloud perturbers may be lurking among nearby stars.'

Scholz's star was first discovered in 2014 by Ralf-Dieter Scholz but unlike other stars around it, it appeared to have an unusual motion in the sky.

A team of scientists from the US, Europe, Chile and South Africa used observations of its motion to trace back its trajectory.

They found that the star is moving away from the Earth at great speed and came alarmingly close 70,000 years ago.

The Oort Cloud is a region filled with icy comets around our solar system, as shown in the graphic above

They calculated that the star, which also has the catchy name WISE J072003.20-084651.2, passed five trillion miles away from our sun (0.8 light years away). Proxima Centauri, our closest neighbour, is 4.2 light years away.

However, even this close it would have been impossible to see the star from Earth with the naked eye as it is far too dim.

The scientists believe it is an active red dwarf star that is about 8 per cent the mass of our own Sun. It is part of a binary star system and is accompanied by a brown dwarf - a failed star that was too small to spark into life.

Even when at its closest to Earth, Scholz's star would have been 50 times fainter than what can normally be seen with the naked eye.

Instead the star would only have been visible with a telescope - technology far beyond our ancestors 70,000 years ago.

However, the star may have occassionally flared and become brighter for a few minutes.

For any of our ancestors who glanced upwards during such a flare, they would have seen it in the area around the Big Dipper.

The astronomers, whose work is published in the journal Astrophysical Journal Letters, calculated that Scholz's star's path would have taken it through the outer areas of the Oort Cloud.

WHAT IS THE OORT CLOUD? 

The Oort cloud is a vast and mysterious region that is thought to surround our solar system.

It contains trillions of comets left over from the birth of the universe - and possibly larger objects like dwarf planets as well. 

It begins at about 0.08 light-years from the sun - 170 times the orbit of Neptune - and extends out to about 0.8 light-years.

Occasionally, comets from the region make their way into the solar system, known as long-period comets.

One of the most famous this year was comet Siding Spring, which brushed past Mars on 19 October.

However, apart from these brief visitors, not much is known about the Oort cloud. It has never been directly observed, and it is not exactly known how large it is - although it is thought to define the gravitational influence of the sun.

The Oort cloud (illustrated) is a vast and mysterious region that is thought to surround our solar system. It contains trillions of comets left over from the birth of the universe - and possibly larger objects like dwarf planets as well. Long-period comets originate here, while short-period comets come from the Kuiper Belt

Large comets in this icy region of space give rise to the comets that enter the innner solar system if their orbits are disturbed.

Simulations of the trajectory of Scholz's star showed that while it passed through this area it is unlikely to have triggered a comet shower.

Until now, the top candidate for the closest flyby of a star to the solar system was the so-called 'Death Star' HIP 8560, which was predicted to come close to our solar system in 240,000 to 470,000 years from now.

However, Mamajek and his collaborators have also demonstrated that the original distance to HIP 85605 was likely underestimated by a factor of ten. At its more likely distance – about 200 light years – HIP 85605's newly calculated trajectory would not bring it within the Oort Cloud.

At its closest, Scholz's star would have been moving across the sky at an 70 arcseconds per year - at this speed it would have moved the distance of the Moon in the sky in 26 years.

Dr Mamajek said: 'The small tangential motion and proximity initially indicated that the star was most likely either moving towards a future close encounter with the solar system, or it had 'recently' come close to the solar system and was moving away.

'Sure enough, the radial velocity measurements were consistent with it running away from the Sun's vicinity – and we realized it must have had a close flyby in the past.'