This is a series of Hubble Space Telescope pictures of comet C/2013 A1 Siding Spring as observed on Oct. 29, 2013; Jan. 21, 2014; and March 11, 2014. The distances from Earth were, respectively, 376 million miles, 343 million miles, and 353 million miles. The solid icy nucleus is too small to be resolved by Hubble, but it lies at the center of a dusty coma that is roughly 12,000 miles across in these images.
When the glow of the coma is subtracted through image processing, which incorporates a smooth model of the coma's light distribution, Hubble resolves what appear to be two jets of dust coming off the nucleus in opposite directions. The jets have persisted through the three Hubble visits, with their directions in the sky nearly unchanged. These visible-light images were taken with Hubble's Wide Field Camera 3.