English
عربي
A star passed through our solar system 70,000 years ago - the nearest ever detected to Earth except the sun, scientists have found.
Space experts from the U.S, Europe, Chile and South Africa have discovered that 70,000 years ago a small, dim red dwarf called nicknamed 'Scholz’s star' came 0.8 light years - or five trillion miles - of our home system.
And they believe the star could have been seen by our ancestors all those millenia ago.
By comparison, it was five times closer than the current closest star, Proxima Centauri. which is 4.2 light years away.
In fact, the star is believed to have passed through the Oort Cloud, the solar system’s distant cloud of trillions of comets a mile wide or more.
The astronomers made the discovery after analysing the velocity and trajectory of the star.
In a paper published in Astrophysical Journal Letters, lead author Eric Mamajek from the University of Rochester and his collaborators noticed Scholz’s star had unusual movement.
Getty Images
Dwarf: The star is far smaller than our solar system's sun. Pictured, a partial solar eclipse is seen over the Sudanese capital Khartoum
Despite being fairly close - 20 light years away - it showed very little motion across the sky.
The team discovered the star is moving almost away from the solar system by using spectrographs on large telescopes throughout the world and computer modelling.
'Most stars this nearby show much larger tangential motion,' said Mamajek, associate professor of physics and astronomy at the University of Rochester.
'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."
Intriguingly, Mamajek adds that there my be "Other dynamically important Oort Cloud perturbers lurking among nearby stars".
The recently launched European Space Agency Gaia satellite is expected to map out the distances and measure the velocities of a billion stars, allowing astronomers to discover other stars that have - and will in the future - pass close to us.
What is Scholtz's star?
The star is part of a binary star system: a low-mass red dwarf star (with mass about 8 per cent that of the sun) and a "brown dwarf" companion (with mass about 6 per cent that of the Sun).
Brown dwarfs are considered "failed stars" their masses are too low to fuse hydrogen in their cores, but they are still much more massive than gas giant planets like Jupiter.
Scholz’s star would have been a 10th magnitude star – about 50 times fainter than can normally be seen with the naked eye at night. It is magnetically active, however, which can cause stars to "flare" and briefly become thousands of times brighter.
So it is possible that Scholz’s star may have been visible to the naked eye by our ancestors 70,000 years ago for minutes or hours at a time during rare flaring events.
