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"Once-in-a-century" ISON comet could be visible from Earth during the daytime

Illustration for article titled Once-in-a-century ISON comet could be visible from Earth emduring the daytime/em

Last year, astronomers using the Russian International Scientific Optical Network (ISON) spied something intriguing just beyond the orbit of Jupiter: a cometary body so large, and with a trajectory that will bring it so close to the Sun, that it could potentially be visible from Earth in the middle of the day (not unlike Comet McNaught, pictured above, was in 2007), and outshine the Moon at night.


The comet, which goes (somewhat uncreatively) by the moniker "ISON," is expected by make its flyby toward the end of this year, as NASA's Tony Philips explains:

Comet ISON is a sungrazer. On Nov. 28, 2013, it will fly through the sun's outer atmosphere only 1.2 million km from the stellar surface below. If the comet survives the encounter, it could emerge glowing as brightly as the Moon, visible near the sun in the blue daylight sky. The comet's dusty tail stretching into the night would create a worldwide sensation.


The question now is whether the comet will, in fact, emerge intact and luminous enough to be worthy of the "Comet-of-the-century" and "dream comet" nicknames currently making the rounds online. According to Philips, the comet could just as soon amount to little more than a disintegrated dud — though Time Magazine's Michael Lemonick lays out a few reasons to be cautiously optimistic:

There's a legitimate possibility this might indeed be the real deal: for one thing, ISON (named for the International Scientific Optical Network, of which discoverers Artyom Novichonok and Vitali Nevski members) was first seen when it was nearly 600 million miles (965 million km) from the Sun, well beyond the orbit of Jupiter. That's unusually distant for a comet to be spotted: these interplanetary chunks of debris usually live in the frigid realms out beyond Neptune and are more or less invisible until solar heat begins boiling ice and dust from their surfaces, forming a light-reflecting halo (known technically as its coma), that makes them seem bigger than they really are.

The fact that ISON can already be seen means it may be reasonably large - perhaps a couple of miles across - which suggests that when it dips to less than a million miles (1.6 million km) above the Sun's fires next November 28, it may be robust enough to avoid the breakup that often happens to smaller comets. And if it does survive, ISON could go on to light up the night sky in the Northern Hemisphere for much of December, 2013 and on into January.

For now, however, perhaps it's best to wait and see what further observation can reveal of the comet's potential. "As it falls toward the sun in the months ahead it will warm up and reveal more about its true character," advises Philips. "By the summer of 2013, researchers should know whether optimistic predictions about Comet ISON are justified."

Read more at TIME, and Discovery News. Read about a past dream-comet-turned-dud at NASA.


Top image via NASA/Stefan Seip

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Simon DelMonte

I remember Kohoutek. And the underwhelming return of Halley's. I won't get excited until we really can see it with the naked eye.