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Our Sun menaces comet 'of the century' ISON with FIERY DESTRUCTION

Could disintegrate, lose tail, meet Bruce Willis ...

The smart choice: opportunity from uncertainty

Skygazers are nervously awaiting the outcome of Comet Ison's impending close encounter with the Sun, which could put paid to hopes that the icy ball will put on a jaw-dropping display across the night sky.

Ison is due to swing round the Sun on 28 November, coming within a mere 1.16 million km of the star's surface. Last week, a camera on NASA's Solar Terrestrial Relations Observatory (STEREO) snapped it apparently largely intact, despite earlier fears that its core had already begun to break up.

Comet Ison seen by NASA's STEREO spacecraft

Also in the frame (animated .gif version here) was Comet Encke, whose wagging tail showed the effects of the solar wind. In 2007, at a time of "near solar minimum" Encke was blasted by a coronal mass ejection (CME) which blew its tail clean off.

Now that the Sun's activity is "near the peak of the solar cycle and eruptions are more frequent", as Angelos Vourlidas of the Naval Research Lab and NASA's Comet Ison Observing Campaign (CIOC) put it - coupled to fact that Ison will pass "~30 times closer to the sun than Encke was in 2007" - the "Comet of the Century" could take a serious pasting.

Fellow Naval Research Lab astronomer Karl Battams enthused: "I would absolutely love to see Comet ISON get hit by a big CME. It won't hurt the comet, but it would give us a chance to study extreme interactions with the comet's tail."

While a CME may not prove terminal, Ison still has to survive possible "Death by Sunburn", as it heats to around 2,760°C at perihelion. Lowell Observatory astronomer Matthew Knight - also a member of CIOC - explains: "Ison needs to be 200m wide to survive; current estimates are in the range 500m to 2km. It helps that the comet is moving very fast so it will not remain long at such extreme temperatures."

However, Knight continues that Ison "faces a double whammy from its proximity to the Sun: even if it survives the rapid vaporization of its exterior, it gets so close to the sun that the sun's gravity might actually pull it apart."

The "best of all possible worlds" scenario would, according to Knight, be if the comet "broke up just a bit, say, into a few large pieces", which would "throw out enough extra material to make the comet really bright from the ground, while giving astronomers pieces of a comet to study for months to come".

We shall see. Assuming Ison pulls through its rollercoaster ride around the Sun, it'll be visible in dawn skies towards the east. ®

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