Nemesis, the Death Star
In 1984, scientists suggested that the Sun had a dark twin, circling far out in space, that every 26 million years sends comets crashing into Earth.
What was reported
In the early 1980s, two palaeontologists argued that mass extinctions in Earth's history seemed to happen in a cycle, roughly every 26 million years. In 1984, two teams of scientists, including a group at the University of California, Berkeley, proposed an explanation: an unseen companion star orbiting the Sun far beyond the planets.
Every 26 million years, its orbit would bring it close enough to disturb the cloud of comets at the edge of the solar system, sending a rain of comets inwards. They named it Nemesis, after the Greek goddess of retribution.
Explanations offered
Infrared sky surveys, including NASA's WISE telescope, have found no such star, and most scientists now doubt the extinctions follow a regular cycle. The idea remains a famous example of a bold scientific guess that didn't pan out.
- When
- Proposed in 1984
- Where
- Berkeley, California, USA
- Witnesses
- Astronomers and palaeontologists
- Status
- Not found
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.
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