ISON appears to have shattered as it reached its closest point to the Sun today, torn apart by the Sun's intense gravitational field.
Three solar observatories were monitoring the comet as it approached the Sun. ISON grew faint in the view of the Solar Terrestrial Relations Observatory and Solar and Heliospheric Observatory. The comet was not visible at all via the Solar Dynamic Observatory, indicating that it may very well have evaporated by that point.
ISON's orbit brought it extremely close to the Sun, but its mass was right at the limit at which it could survive such a trip, making the Thanksgiving observations a nail-biter. Viewers on Earth were hoping for ISON to survive, putting on a show in the night sky as it reemerged from behind the Sun. But it looks now like the comet will have been totally destroyed, leaving nothing left to light up the night.
NASA's Solar Terrestrial Relations Observatory and the ESA/NASA Solar and Heliospheric Observatory show Comet ISON dimming as it journeyed toward the Sun.
Few sungrazing comets survive their trip to our solar system's home star. Not only must these small, loosely bound collections of ice and dirt withstand the Sun's gravity, the extraordinary heat of the Sun's corona weakens a comet as it warms it, making it much easier for gravity to stretch and break the nucleus -- not unlike the way a popsicle basking in the Sun of a hot day is more likely to slide off its stick than one fresh from the freezer.
A white plus sign shows the location where Comet ISON would have appeared in this Solar Dynamics Observatory image if it survived its encounter with the Sun. Credit: SDO
ISON may be no more, but it will live on in the data meticulously collected by astronomers over the past few months. New sungrazing comets from the far-distant region called the Oort Cloud are infrequent, and the observations of ISON will help us understand much more about these comets, the Oort Cloud where they reside, and the conditions in which they formed.