Comet C/2001 C2 (originally designated SOHO-294) was discovered in LASCO C3 images on 6 February 2001
Solar radiation heats the comet which in turn causes the outgassing of the water molecules and dust. The dust scatters sunlight at visible wavelengths, making the comet bright in LASCO images. The water molecules break down into oxygen and hydrogen atoms, and the hydrogen atoms interact with the coronal plasma. The hydrogen atoms scatter Lyman Alpha (1215 Angstroms) radiation from the Sun. The UVCS images represent the brightness at this wavelength.
Several properties of the comet and the encountered coronal environment can be determined from this observation. The outgassing rate of water molecules was calculated at ~100 kg/s and the size of the cometary nucleus was on the order of 10 meters during the UVCS observations. The comet also acted as a probe for the determination of coronal conditions. Densities of about 10,000 particles per cubic centimeter at 4.82 Ro and 86,000 particles per cc at 3.32 Ro were found. This sharp increase suggests that the comet passed from a fast solar wind region to a denser slow solar wind area. All of the results presented here are preliminary estimates.
Credits: Thanks to Doug Biesecker (LASCO) for his early reporting and position estimates, Brian Marsden for the orbit prediction, and the UVCS ops and science teams (Michael Uzzo, Kuen Ko, Rai Wu, John Raymond) for making this observation possible.