January 24, 2010
The observations of the comet C/2009 R1 (McNaught) continued in the early morning hours on 21 June 2010 with the Coude spectrograph of the 2-m Ritchey-Chretien-Coude (RCC) Telescope of NAO Rozhen. High resolution spectra (0.0678 Å/px) in the ultraviolet region were obtained with the aim to resolve and analyze the rotational lines of the cyan B2∑+ - X2∑+ (0,0) transition.
The upper part of the figure shows the "raw" image spectrum. The lower part is the total spectrum, obtained by summing all the rows in the raw images. The total integration time is 54 minutes. The emission lines are produced by "resonance-fluorescence". This is a physical process in which molecules are excited to an upper level by absorption of solar photons and subsequently relax back to the ground state by emitting at the wavelengths of the absorbed photons. Each emission line corresponds to the transition of electrons between the rotational energy states of the CN molecule. The obtained spectra provide the opportunity to measure the ratio of different isotopes of carbon (12C/13C) and nitrogen (14N/15N). The isotopic ratio of 14N/15N derived from other comets is about 140 and it is remarkably low compared to the terrestrial value of 272. Which value corresponds to the primordial material of the solar system? Or the conditions in the protoplanetary cloud have been highly different at the places where the Earth and comets formed? Answers of these questions will be sought in the details of the obtained spectra.
For more information please contact Dr. Galin Borisov (gborisov@astro.bas.bg).