Comet ISON’s Dawn Spectacle – Part I

A bright new comet is on its way to gracing the pre-dawn morning sky toward the end of November and promises to put on quite a show during the first few weeks of December.  Due to the time frame involved—and its potential for becoming the “Comet of the Century” as it’s being widely heralded—we’re devoting the Sky Talk columns both this month and next to its coverage.

A comet predicted to be of historic proportions is rapidly heading for the Sun.  Known as Comet ISON, it’s one of a multitude of such interlopers from the outer solar system constantly being picked up by automated sky surveys at professional observatories around the world.  (This one was found in Russia as part of the International Scientific Optical Network—thus the designation “ISON.”)  But few of them ever become naked-eye spectacles like ISON will be, or as Comet Pan STARRS was back in March.  Hunting for comets visually through telescopes was long a traditional pursuit of amateur astronomers, and were named after their discoverers. But photography, and later electronic CCD imaging, has largely replaced visual discoveries, and today nearly all new comets are found though such automated surveys.  (Readers should note, however, that some are still being picked up by stargazers sweeping the sky for them!)

It’s well known that comets are notorious for not living up to predictions (famed Comet Halley not meeting expectations at its 1986 appearance, being one striking example). But astronomers are confidently saying that Comet ISON will be anything but disappointing during its apparition later this month (and especially so during December, which we will cover in the next installment).  Here’s what to expect now. The comet will become visible to unaided eye in the predawn east-southeastern sky about two weeks before rounding the Sun on the 28th.  It’s expected to reach 2nd or 3rd magnitude before disappearing into the morning twilight about a week prior to that date.  Binoculars will definitely enhance the view and should show a tail projecting from the head of the comet.

ISON is what is known as a “sungrazing comet” and it will pass just one solar diameter from our Daytime Star at its closest approach!  Around that time it will briefly become as bright as magnitude -6, which is dozens of times more radiant than the planet Venus ever appears.  This will happen in broad daylight and the comet’s nucleus will be visible—but only to highly experienced observers using extreme safety precautions.  The nucleus may fragment or even possibly partially evaporate from the intense heat of the Sun, as has happened to other sungrazers in the past.  We’ll just have to wait and see!

Before closing this part of our coverage, mention should be made that observers along the East Coast of North America will see the Sun rise at dawn on November 3rd with a small “bite” taken out of its edge resulting from a solar eclipse occurring over theAtlantic Oceanthat morning.

— James Mullaney

Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing.  His latest, Celebrating the Universe!, is available from