Comet K2
NASA, ESA and David Jewitt
This Hubble Space Telescope image, taken in June 2017, shows a fuzzy cloud of dust, called a coma, surrounding the comet known as K2, the farthest active comet ever observed entering the solar system. Hubble photographed images of K2 when the frozen visitor was 1.5 billion miles from the sun, just beyond Saturn's orbit. Even at that remote distance, sunlight warms the frigid comet, producing an 80,000-mile-wide coma that envelops a tiny, solid nucleus.