Comet ISON is on the home stretch, rocketing toward the sun for its Thanksgiving rendezvous with the roiling orb.
Over the course of November it has behaved slightly erratically for a comet, astronomers say, taking on strange hues, such as blue—fueling speculation by some about a possible Hopi prophecy involving a blue planet that would smash into Earth—and at one point appearing to begin fragmenting.
Instead of breaking apart, the comet burst into brilliance and brightened 25-fold, Space.com reported, doubling in radiance between November 19 and 20 alone.
“Along with this surge in activity, soaring rates of dust and gas were being released from its nucleus,” Space.com said. “In the wake of this recent activity, experienced comet watchers are growing more confident that the comet has a chance to be ranked among one of the brightest in the last half century.”
What transpires on Thanksgiving Day, at 1:38 p.m. Eastern Standard Time to be exact, will determine whether that happens. That is the moment, astronomers have calculated, that ISON will be 730,000 miles from the sun, whipping around it in a hairpin turn at a maximum velocity of 844,632 mph.
What happens after that is anybody’s guess. If the sun’s heat and the comet’s length of exposure to it drag on too long, the thing could simply burn up and flare out. But given its behavior so far, ISON may very well whip around the sun and slingshot out the other side, tail blazing, and entertain us for all of December, climbing higher and higher in the sky as it journeys back to the outer solar system.
In other words, if ISON survives its brush with the sun, it may very well be visible even in daylight for a brief time. Stranger things have happened. In 2011, against all odds, comet Lovejoy C/2011 W3 made just such a plunge, and lived.
As it happens, currently another sun-grazing comet Lovejoy, number C/2013 R1 (discovered by Australian amateur astronomer Terry Lovejoy, as was its 2011 predecessor), is also hurtling toward the sun, though it is behind ISON. The 2013 Lovejoy—the astronomer has discovered four comets to date—will take its own sun dive on Christmas Day, according to TimeandDate.com.
ISON has even more company. Throughout November, invisible to us on the ground, four comets in total have been passing by. One of them is comet Encke, shown here in a time-lapse video using data from a NASA observation spacecraft, appearing to race with ISON as its tail flutters in a solar wind.
Earlier this year comet PAN-Starrs made a similar journey, though it did not turn as bright as astronomers hoped it would.
Comet ISON, if it survives, will be visible through much of December, lingering in the sky all night long on Christmas, Space.com said. The next day at 5:42 p.m. EST, ISON will make its closest approach to Mother Earth, passing 39,897,562 miles away. As usual, the darker the skies the better; the best vantage points will be out in the country.
“From rural areas, where the night skies are still reasonably dark, the comet could evolve into a celestial showpiece—perhaps even a showstopper,” Space.com said. “Conversely, from major metropolitan areas under urban, light polluted skies, viewers will be largely disappointed.”