Seventy thousand years ago our world, unmarked by agriculture and industry, was a very different planet. Back then Earth was shared by at least four separate types of human being. Tough and sturdy Neanderthal folk hunted mammoths and built huts across the chilly forests, mountains and plains of Eurasia. Further east the mysterious Denisovan people settled the alpine valleys of Siberia’s Altai Mountains. Tiny Homo floresiensis made a warmer home in the rainforested islands of today’s Indonesia, carefully avoiding giant monitor lizards, the local apex predators. Meanwhile in Africa our direct ancestors bided their time, never dreaming that one day that all of this wonderful planet would be their’s alone.
All four kinds of human looked different but shared common behaviour and technology. All chattered to each other in their own languages, used stone tools and lit up the darkness with fires. As they gathered around their hearths, these ancient peoples will have looked to the night sky and marvelled at what they saw; it’s a very human thing to do. Among the wonders of the sky they shared may have been something we do not have today, a neighbouring star roaming through the outer edge of the Solar System.
Today Scholz’s Star is about 20 light years from the Sun in the constellation of Monoceros. An old and very small red dwarf (its mass is only 8% of the Sun’s), Scholz’s Star is the primary of a binary system. Its companion is only a little smaller (6% of the Sun’s mass) but is too small to generate energy by nuclear fusion in its core making it a “failed” star or brown dwarf. The pair just lie on either side of the balance point between enough and too little mass for fusion. This is interesting but more startling still is the duo’s speed and trajectory through the Galaxy, what astronomers call its “proper motion”. Seen from our Solar System, Scholz’s Star barely moves across the across the sky. In fact careful radial velocity measurements (based on observations of the Doppler shift of emission lines in the star’s spectrum) indicate that the star is rapidly moving almost directly away from the Solar System.
This implies that Scholz’s star was once much closer to the Sun (and Earth), possibly very close indeed. Simulations of the star’s orbit through the Galaxy performed by astronomers led by Eric Mamajek from the University of Rochester suggests that about 70 000 years ago it probably passed about 0.8 light years (52 000 au) from the Sun*. No other star is known to have made so near an approach to our Solar System. In contrast, most people can tell you that today the Sun’s closest neighbour is Proxima Centauri at 4.2 light years distant. This close approach means it passed through the outer part of the Sun’s Oort Cloud, the vast spherical shell of comet nuclei which surrounds the Solar System. Although astronomers theorise that a close approach by a star can perturb the Oort Cloud provoking a spectacular “comet shower”, the passage of Scholz’s Star was probably too distant, passing through the Cloud’s sparsely-populated outer fringe, to cause this. Anyone anticipating an influx of new comets sent our way by the passing star will be disappointed, any comet dislodged from so distant an orbit would take about two million years to reach the inner Solar System.
Red dwarfs make up in number 80% of the stars in the Universe, but they are very dim; none can be seen from Earth without a telescope. From Earth, even at its closest Scholz’s Star would normally have been magnitude 10, invisible to the eyes of our ancestors and their cousins. However about 40% of red dwarfs possess powerful magnetic fields which cause them to undergo spectacular episodes of “flaring”, during these events the star’s brightness can increase more than a thousandfold for minutes or hours at a time. Scholz’s Star is one of these flare stars, so it is just possible that during its flyby of the Sun it could have experienced one of these eruptions, brightening to a visible magnitude and so might have been observed by ancient humans.
*The dating and distances quoted above are not “set in stone”, Mamajek and his collaborators calculate the star passed within 38-75 thousand au from the Sun and that this happened 60-85 thousand years ago.
(Scholz’s Star is formally known as WISE J072003.20-084651.2, however its nickname honours its discoverer, German astronomer Ralf-Dieter Scholz of the Leibniz-Institut für Astrophysik Potsdam.)
- This star is not nor ever has been part of our Solar System
- This star will not in any way effect our planet or Sun gravitationally or electromagnetically- it is too far away.
- It is not linked to any mythological or real disaster.
- Its gravitational pull will not have effected the orbits of the planets- again it never came close enough to cause this.
- It is and was not known as “Nibiru”
- It was not known to, observed or recorded by any the Sumerians, Mayans or any other ancient or historical near Eastern or Meso-American civilisation.
(Article by Colin Johnston, Science Education Director)