An asteroid discovered just weeks ago has become the most threatening object yet detected in space. A preliminary orbit suggests that 2002 NT7 is on an impact course with Earth on 1 February 2019, although the uncertainties are large. Astronomers have given the object a rating on the so-called Palermo technical scale of threat of 0.06, making NT7 the first object to be given a positive value. From its brightness astronomers estimate it is about 2km wide, large enough to cause continent-wide devastation on Earth. Although astronomers are saying the object definitely merits attention, they expect more observations to show...