In 1984, a team of paleontologists discovered a pattern to the extinctions in the geologic record. There was a major extinction event every 26 million years. This cycle goes back over 260 million years, with evidence of the mass extinctions being missing for just two out of the 10 possible iterations in that span. The question went out: what could cause extinctions on a 26 million year cycle?
Two different teams of astronomers independently came up with a very similar answer. What if we actually live in a binary star system? If a dim red dwarf or brown dwarf star circled our sun every 26 million years, it could do it. This star (dubbed "Nemesis" or "the Death Star") would pass through the Oort cloud (a cloud of comets out past Pluto) every cycle, bringing with it a ton of comets disturbed from their normal orbits by gravity. There's a high likelihood that at least one of them would crash into the earth. This would kick up enough debris to choke out the sunlight. The comets might also carry great amounts of iridium to our planet. The combined calamities of hundred-mile long impact crater, decreased sunlight and temperatures, and increased pollution and poisoning, could potentially wipe out the vast majority of species on our planet.
Currently, Nemesis (if it exists) is believed to be 1.5 light years away in distance. Since it moves much more slowly than light, we've got another 10 million years or so before the next near pass and rain of comets. By the time it gets here, we'll either have long since destroyed ourselves, or be sufficiently advanced to survive the disaster.
Game and Story Use
- You could conflate the Nibiru Collision with Nemesis, or introduce some other explanation to make the next passage come sooner - say, 2012?
- Rather than fudge the predictions by 10 million years, a similar problem could be facing another planet in a space opera setting just a few hundred years from now. The heroes have to save that planet from it's Nemesis star.
- Spacecraft traveling beyond our solar system might use Nemesis as a gravitational slingshot to help accelerate on to other stars.
- Or the astronauts leave on a mission elsewhere, and just like in the original Planet of the Apes, the Twin Paradox means they experience just a few years while the earth advances by a huge amount of time. They return to an earth being pummeled by comets. Whatever Planet of the Apes Ending they were expecting is instead obliterated by the cometary impacts.
- Perhaps Nemesis has a few planets of its own, which once supported life before it burned dim, or before it got caught in the gravity of our sun. These precursors might have left ruins or even a megastructure behind. Perhaps we don't see Nemesis because most of its light is blocked by a Dyson Sphere.
- If this ancient Stellar Engine can be brought back on line, all future Nemesis impacts can be prevented.
- Maybe Nemesis isn't a red dwarf, maybe it's a very small black hole - this could pose a significant navigational hazard to the first few spaceflights to attempt to leave our solar system.