Destruction of Sun-Grazing Comet C/2011 N3 (SOHO) Within the Low Solar Corona

Star Grazing Some comets come perilously close to the Sun. Schrijver et al. (p. 324; see the Perspective by Lisse) describe observations made by the Solar Dynamics Observatory of one such Sun-grazing comet, which penetrated into, fragmented, and completely sublimated within the solar atmosphere. More than 2000 Sun-grazing comets have been observed in the past 15 years but none could be followed into the Sun's atmosphere. By showing that comets can be observed at such small distances from the Sun, this study opens up new ways to study comets and also the solar atmosphere. The NASA Solar Dynamics Observatory detected and tracked a comet as it penetrated the solar atmosphere. Observations of comets in Sun-grazing orbits that survive solar insolation long enough to penetrate into the Sun’s inner corona provide information on the solar atmosphere and magnetic field as well as on the makeup of the comet. On 6 July 2011, the Solar Dynamics Observatory (SDO) observed the demise of comet C/2011 N3 (SOHO) within the low solar corona in five wavelength bands in the extreme ultraviolet (EUV). The comet penetrated to within 0.146 solar radius (~100,000 kilometers) of the solar surface before its EUV signal disappeared. Before that, material released into the coma—at first seen in absorption—formed a variable EUV-bright tail. During the final 10 minutes of observation by SDO’s Atmospheric Imaging Assembly, ~6 × 108 to 6 × 1010 grams of total mass was lost (corresponding to an effective nucleus diameter of ~10 to 50 meters), as estimated from the tail’s deceleration due to interaction with the surrounding coronal material; the EUV absorption by the comet and the brightness of the tail suggest that the mass was at the high end of this range. These observations provide evidence that the nucleus had broken up into a family of fragments, resulting in accelerated sublimation in the Sun’s intense radiation field.