By now, Comet ISON has traveled more than 100,000 astronomical units—about 2,500 times the distance between the sun and Pluto—and on Thursday, it is projected to miss the sun by just 730,000 miles. That's when its million-year journey will end in either death or fanfare: The sun could destroy it by way of radiation, pressure, or a tail-ripping solar burst; or ISON could evaporate to survive the encounter and rebound past Earth—to provide what star-gazers hope will be a naked-eye spectacle.
"I believe the next couple of days will be crucial to determine the post-perihelion appearance of the comet," says Padma Yanamandra-Fisher, of the Space Science Institute. "Perihelion" describes the point in orbit when an object is closest to the sun.
On the other hand, Karl Battams, an astrophysicist, wrote on the NASA Comet ISON Observing Campaign's blog that "the last time we saw an object like this was never," adding that a sungrazing comet just three days from perihelion is too new an object to warrant any conclusions.
If it doesn't survive Thursday, the rocky material that remains of ISON could simply continue to orbit the sun.
Show or no show, why not celebrate spectacular mortality by going out with NASA's Comet ISON toolkit in spite of uncertainty and preparing for something great?