Starship Asterisk*

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Incoming Comet ISON Appears Intact to NASA's Hubble

A new image of the sunward plunging comet ISON suggests that the comet is intact despite some predictions that the fragile icy nucleus might disintegrate as the Sun warms it. The comet will pass closest to the Sun on November 28.

In this NASA Hubble Space Telescope image taken on October 9, the comet's solid nucleus is unresolved because it is so small. If the nucleus broke apart then Hubble would have likely seen evidence for multiple fragments.

Moreover, the coma or head surrounding the comet’s nucleus is symmetric and smooth. This would probably not be the case if clusters of smaller fragments were flying along. What's more, a polar jet of dust first seen in Hubble images taken in April is no longer visible and may have turned off. This color composite image was assembled using two filters. The comet's coma appears cyan, a greenish-blue color due to gas, while the tail is reddish due to dust streaming off the nucleus. The tail forms as dust particles are pushed away from the nucleus by the pressure of sunlight.

The comet was inside Mars' orbit and 177 million miles from Earth when photographed. Comet ISON is predicted to make its closest approach to Earth on December 26, at a distance of 39.9 million miles.

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

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This new NASA/ESA Hubble Space Telescope picture shows C/2012 S1, better known as Comet ISON, a high-profile celestial visitor to the Solar System. Hubble has already snapped this comet twice this year (opo1314a, opo1331a), but for some time it was temporarily blocked from view by the Sun. It was spotted again in August 2013, and this new image shows the comet as it appeared in our skies in early October.

ISON will be brightest in our skies in late November, just before and after it hurtles past the Sun. As it gets brighter, it may even become visible as a naked eye object, before it fades throughout December — the month of its closest approach to Earth. Depending on its fate as it passes close to the Sun, it could become spectacular or, on the contrary, it could completely disintegrate. Many observatories, as well as several ESA and NASA missions, aim to observe this icy visitor over the coming months.

In this Hubble image, taken on 9 October 2013, the comet's solid nucleus is unresolved because it is so small. If it had broken apart — a possibility as the Sun slowly warms it up during its approach — Hubble would have likely seen evidence for multiple fragments instead.

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)