It was one heck of a roller coaster ride for astronomers tracking comet ISON as it swung in for its close passage by the sun. A week out, it brightened in an outburst that some took to be its death throes as the blistering heat of the sun ate into the ice and dust of its kilometer-wide nucleus, which appears to be more of a loose, dirty snowdrift than a firmly packed iceball. But it steadied, continued to brighten, only to start fading. The end? No, it recovered, resumed brightening only to be lost from view by the orbiting solar telescopes. They were able to gaze directly at the sun (here seen in time-lapse images, the center white circle representing the sun) just as the comet drew near its closest approach to the sun on 28 November. Most astronomers thought ISON was a goner, the victim of the searing heat and the sun’s wrenching gravitational tides. But then, out the other side, came ISON, or something that had been ISON. There might be a much-diminished nucleus or just a swarm of icy debris. Whatever it is, however, it is spewing the gas and dust that, if ISON can keep it up, could make for a pretty sight in the predawn of the early days of December. Knowing ISON as they do, astronomers are calling that a huge if.
ScienceShot: Comet ISON Survives Its Solar Gantlet
Richard A. Kerr