Recent revelations that our corner of the galaxy was visited by an alien star in the distant past have once more raised questions about our own solar system, rekindling suggestions that another Earth-sized planet could lie hidden on the opposite side of the Sun, or that an unknown companion star could be orbiting beyond our view.
Last week, it was announced that researchers have discovered that a Red Dwarf star, accompanied by a smaller Brown Dwarf, passed through the edge of our solar system just 70,000 years ago. Named Scholz's Star, after its German discoverer Ralf-Dieter Scholz, the alien visitor reached a point 0.8 light years distant from our Sun, moving through the Oort Cloud that surrounds our system.
The discovery seemed at first to validate a theory posited in 1984 by Richard Muller of the University of California Berkley that a companion star, called Nemesis, might orbit the Sun at a great distance, responsible for mass extinctions on Earth that occur more frequently every 27 million years. If a companion star or rogue planet were to pass through the Oort Cloud at those intervals, some scientists assert that they could be responsible for sending a volley of comets towards the Sun, accounting for a rise in impact rates on our planet, and therefore extinctions.
RT@telluric #NemesisStar called Scholz passed close to Earth when Neanderthals ruled Eurasia. http://t.co/jGtnBDHeF7 pic.twitter.com/iXe6xQwjAR
— Asteroid Initiatives (@AsteroidEnergy) February 19, 2015
Though similar theories have been advanced about a hidden planet residing on the opposite side of the Sun, the forces of gravity seem to stand against these ideas. The gravitational fields of both the Sun and the other planets subtly affect the Earth, and though there are points of stability in an orbit where a small enough object can be located, the eventual result of a hidden planet would be to alter the Earth's path.
Writing for Universe Today, Fraser Cain recently discussed the consequences of such a hidden planet behind the sun.
"Eventually, our orbits would intersect, and there'd be an encounter. If we were lucky, the planets would miss each other, and be kicked into new, safer, more stable orbits around the Sun. And if we were unlucky, they'd collide with each other, forming a new super-sized Earth, killing everything on both planets, obviously."
A Nemesis star would fare no better, according to researchers. In order to avoid revealing itself by affecting orbits within the solar system, such a star would have to remain at a great distance from the Sun, in a path that would be inherently unstable.
With Scholz's Star already 20 light years distant and moving away from our solar system, theories of a Nemesis star or hidden planet behind the Sun remain unproven.
[Image via TechieTonics]