Results from UVCS and LASCO Observation of the Sungrazing Comet C/2000 C6

Abstract

During 2000 February 9È10, the Large Angle Spectrometric Coronagraph and Ultraviolet Coronal Spectrometer (UVCS) instruments aboard the Solar and Heliospheric Observatory observed comet C/2000 C6, a member of the Kreutz family of sungrazing comets. A tail nearly 0.5 in length was detected in R _ Lya emission. UVCS was able to observe the comet at four heights as it approached the Sun. A jump in the Lya brightness between 5.71 and 4.56 suggests that the nucleus fragmented, exposing more area R _ to solar illumination and increasing the outgassing rate. We interpret the Lya luminosity in terms of the outgassing rate and use this to estimate the diameter of the nucleus. The Lya emission fades as H I is ionized, providing estimates of the density in the coronal streamer encountered by the comet. Subject headings : comets : general È comets : individual (C/2000 C6) È solar wind È ultraviolet : solar system