Based on a strange clue, astronomers have found a collection of young red dwarf stars in space that may have gobbled up rocky planets — perhaps similar worlds to Earth.   Like sniffing a teenager's breath for alcohol or cigarette smoke, researchers noticed the stars had more lithium in their atmospheres than they should. That could mean they still had the stench of their last meal on them.  A red dwarf is a small, cool type of star, and lithium is a lightweight chemical that stars eventually destroy through nuclear reactions. In stars like these, lithium usually disappears early in life because the stars' hot interiors incinerate it. By the time these stars reach adolescence — around 50 to 200 million years old — astronomers expect little to no trace of lithium. But a team found six stars out of thousands surveyed that broke the rules in a new study published in Monthly Notices of the Royal Astronomical Society .…