Scientists were already predicting it: Comet ISON would be visible to the naked eye at the end of November, despite the fact that the point of closest approach to Earth would not occur until December. However, a burst of activity has advanced that moment and can already be observed thanks to the increase in its brightness.
Comets are small solid frozen bodies that change as their temperature increases as they approach the Sun. Basically, when they heat up, they evaporate (sublimate), dragging with them small grains of dust that, when free, reflect light and give rise to coma ( the diffuse central stain that surrounds the nucleus) and the typical tails. They are normally very stable in terms of visibility, but sometimes, as has happened in this case, their brightness suddenly increases to the point of being seen with the naked eye earlier than expected .
“A possible explanation for the outburst is that the axis of rotation has been quite aligned with the Sun-comet direction, so that only one hemisphere of the cometary nucleus has received radiation and there may be” fresh ice “ (in the other hemisphere). that have hardly received sunlight until now. As ISON gets closer to the sun, the position of the subsolar point on the comet will also change and, therefore, there will be parts that were previously in shadow that suddenly receive radiation and can sublimate “, explains José Luis Ortiz, researcher at the Institute of Astrophysics of Andalusia.
And it is that in the Institute of Astrophysics of Andalusia, belonging to the CSIC, they are participating in various observation campaigns prepared to study before and after its passage through perihelion, the point of maximum approach to the Sun. This analysis will allow them to know its characteristics and its activity before it reaches the point of closest approach to our planet . To observe it, the researchers use the IRAM 30-meter radio telescope.
The so-called “comet of the century” is not a common object. Discovered on September 21, 2012 by a group of Russian astronomers, it is a comet that comes from the Oort cloud, a bubble that surrounds the Solar System. This cloud is believed to be made up of the remains of the nebula that gave rise to the Sun and the planets about 4.6 billion years ago.
The comet will pass, according to scientists’ estimates, only about 1.8 million kilometers from the Sun (2.7 solar radii) on November 28. This proximity will make it reach temperatures of about 5,000 ºC which probably produces the sublimation of ice, silicates and even metals . Said sublimation will have a direct visual effect in the form of shine, although it can also happen that it ends up fragmenting or vaporizing and disappearing.
