As it continues to hurtle toward the Sun, Comet ISON – also designated C/2012 S1 – seems destined to pass within 730,000 miles of our star on 28th November; a path that astronomers had previously charted before the icy body made its appearance in our night skies this month.
As it gets closer to the intense heat of the Sun, warmth meets cold. If ISON can stand the heat and still remain relatively intact, the meeting of extreme temperatures will cause the great traveller’s ices to transform from solid to gas quickly – or subliminate – leading the comet to brighten noticeably.
If you have been tracking ISON, then you will notice that there has already been evidence of some brightening during the second week of this month when a sudden outburst caused the comet to appear 10 to 16 times brighter. As a result, ISON is theoretically visible to the naked eye under extremely dark skies glowing as a faint smudge at a magnitude of around +5.4. However, it is much more prominent through 10×50 binoculars and small telescopes.
Recent images of the comet by scientists at the Max Planck Institute for Solar System Research in Germany and the Wendelstein Observatory of the Ludwig Maximilians University of Munich, suggest that fragments may have detached from ISON’s nucleus during the past few days. Whether the fragmentation is related to the icy body’s recent outburst is not certain but, in the case of other comets, there is a strong connection between both events suggesting that it is likely. Calculations carried out by researchers imply that ISON didn’t lose a great deal of material. However, once fragmentation happens once, it almost always happens again.
To find ISON, look for Virgo in the eastern pre-dawn sky where it can be seen rising at around 4am and locate the constellation’s prominent first magnitude star, Spica. The comet’s head should appear below this variable blue giant – which ranks as the fifteenth brightest star in the night sky – with the comet’s tail just in front of it.
Predictions are, as the week progresses that ISON should reach fourth magnitude around 21st November where it will hopefully appear at a decent brightness in the eastern sky around an hour before sunrise.
During the first week of December and, if it survives its close encounter with the Sun, observers hope for a brightness greater than first magnitude. This means that we should hopefully get better views of ISON in the run up to Christmas.
PLEASE NOTE: As ISON gets closer to the Sun it will get lost in our star’s glare and you should avoid searching for it. It is extremely dangerous to look at the Sun. It will be safer to view the comet as it moves away from the Sun in December.
Image courtesy of Wendelstein Observatory of the LMU/MPS (bottom)