Mystery behind 'Comet of the century' ISON's final hours revealed

A new data analysis from ESA/NASA Solar and Heliospheric Observatory (SOHO) spacecraft has revealed the final hours of comet 2012/S1 (ISON).

It was found that during the final phase of the approach to perihelion (its nearest approach to the Sun); the comet's tail became increasingly faint. It was clear that ISON stopped producing dust and gas shortly before it raced past the Sun and then the nucleus completely disintegrated.

Hours before ISON reached perihelion, stunning images taken by SOHO's Large Angle and Spectrometric Coronagraph (LASCO) showed the bright, elongated tail of the onrushing comet. Unfortunately, ISON's trajectory took it so close to the Sun about 1.2 million kilometers above its visible surface that the final phase of the encounter was obscured by LASCO's occulting disc, which blocks light from the Sun to create an artificial solar eclipse.

When comet ISON was discovered in the autumn of 2012, astronomers hoped that it would eventually light up the night sky to become a "comet of the century". Orbital analysis showed that the sungrazing intruder from the outer reaches of the Solar System would pass only 1.2 million kilometres above the Sun's visible surface on 28 November 2013.

Werner Curdt from the MPS, said that the only instrument that could obtain serviceable data at this time was Solar Ultraviolet Measurements of Emitted Radiation (SUMER).

Bernhard Fleck, ESA's SOHO project scientist, said that observations such as those made of comet ISON show that the observatory still has an important role to play in improving the understanding of the Sun and its influence on the planets and other objects which orbit around it.

The study is published in the journal Astronomy and Astrophysics.