Nasa scientists spy 'largest comet ever seen'

A comet with a nucleus 50 times bigger than normal is barrelling towards Earth at 22,000 miles per hour. Nasa's Hubble telescope has determined the comet's icy nucleus has a mass of about 500 trillion tonnes and is 85 miles (137km) wide - larger than the US state of Rhode Island.
But not to worry. The closest it will get is one billion miles away from the Sun, and that won't be until 2031.