A mysterious "rogue planet"  has been observed gobbling six billion tons of gas and dust a second — an unprecedented rate that blurs the line between planets and stars, astronomers said Thursday. Unlike Earth and other planets in our solar system, which orbit the sun, rogue planets float freely through the universe untethered to a star. Scientists estimate there could be trillions of rogue planets in our galaxy alone — but they are difficult to spot because they mostly drift quietly along in