Careful sleuthing through decade-old images has enabled ESA’s asteroid team to decide that a newly discovered space rock poses little threat of hitting Earth any time soon.
Spotting a previously unknown asteroid for the first time always raises the big question: is there a risk it will impact Earth?
Yet, upon discovery, analysts often have very little to go on. The initial image from the observatory, survey team or individual backyard astronomer who spotted the rock typically gives only basic information – its location in the sky and its brightness – and sometimes these aren’t known terribly accurately.
The most crucial information needed to determine with any degree of confidence whether it is a ‘near-Earth object’ (NEO) – and that it will miss Earth (or not) – is the new object’s path. And determining that requires a series images acquired over a period of days or even months.
“We need multiple follow-on images to compute the trajectory and make a risk estimate, but even then the uncertainty can be very large. It really takes many months of observations to get a good, reliable impact risk estimate, and in the meantime, there can be reason to worry,” says Ettore Perozzi of the NEO Coordination Centre at ESA’s facility in Italy. … (ESA)