[单项选择]When the end of the world comes, we’ll know what to blame. Scientists have found compelling evidence that the Sun has a baby brother, a dark star whose eccentric orbit is responsible for periodically showering the Earth with comets and meteorites.
The dark star—named Nemesis by astronomers—is thought to be a brown dwarf that spins round the Sun in an orbit so large that it is measured in light years, the distance light travels in a year, equivalent to about 6,000 billion miles.
The research suggests that, every 26m years, the star’s eccentric orbit brings it within one light year of the solar system. There it causes havoc in the Oort Cloud, a huge region surrounding the solar system that contains billions of bits of cosmic rubble left over from the formation of planets.
Of the millions of rocks it throws out of orbit at each visit, some hurtle earthwards—and have several times nearly wiped out life on Earth.
Astronomers have long wondered if the Sun has a smaller pa
A. Brown Dwarf Orbits around the Earth
B. Sun’s Hidden Twin Stalks Earth
C. Oort Cloud and Comet Shower
D. Star, Planet and Dwarf