As of mid-November, ISON is officially upon us. Using Hubble, we've taken our closest look yet at the innermost region of the comet, where jets of sublimating ice are fueling a spectacular tail.
Visit Hubble Heritage for high-resolution images. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Made from observations on November 2nd, the image combines pictures of ISON taken through blue and red filters. As Hubble follows the close, fast-moving comet, background stars are streaked in the direction of ISON's motion. The combined effect, which has been removed from the final image, can be seen here:
A stacked color composite of the November 2nd observations. Since
Hubble tracked the comet, each red and blue image of ISON itself adds up
in the same place, producing a clear, colorful image of the comet. The
smeared-out background stars don't fare so well. Also visible are cosmic
rays, which can be seen as small streaks angled in random directions, and
the chip gap: a horizonal dead zone in the middle of the image.
Credit: Hubble Heritage Team
As we expect, the spherical coma around ISON's nucleus is blue ...