The Bernardinelli-Bernstein comet was first detected seven years ago and is thought to be up to 100 miles wide - nearly 12 times the size of Mount Everest.
The impressive comet was spotted by and named after University of Pennsylvania astronomers Pedro Bernardinelli and Gary Bernstein.
“The story told by the comet would tell us of what existed in the solar system billions of years ago," Bernardinelli told The Daily Beast.
The comet is believed to be between 60 and 100 miles wide, making it the largest ever witnessed by a human being and about 1,000 bigger than average.
While the comet is expected to reach the inner solar system in about a decade, astronomers say it poses no threat to Earth.