New Measurements of the Solar Disk-Center Spectral Intensity in the Near IR from 645 Nm to 1070 Nm

At the high-altitude station on Terskol Peak (central Caucasus, 3100 m) by the Main Astronomical Observatory of the National Academy of Sciences of the Ukraine in 1992, spectral measurements of the solar disk-center intensity for the near IR region were performed. These measurements are a continuation of the solar absolute spectral energy distribution investigation programme. Data published earlier (Burlov-Vasiljev, Gurtovenko, and Matvejev, 1995a) are expanded now in the long-wave spectral region up to 1070 nm. The measurements were made with the specialized solar telescope SEF-1. The method of comparison of the solar disk-center brightness with the brightness of the calibrated region of a standard ribbon tungsten lamp was used. The atmospheric extinction was taken into account with Bouger's long method accompanied by the parallel-independent control of atmospheric stability. The uncertainty of the absolute solar disk-center intensity values is estimated to be 2% in regions free from the strong telluric absorption of atmosphere oxygen and water vapour. In these regions an additional reduction was carried out, which was derived from the synthetic atmospheric absorption spectra computed on the basis of the molecular parameter data and the standard model of the Earth's atmosphere. The 1-nm integrals of the disk-center radiance in the wavelength range 650–1070 nm, which are established on 5-day measurements in March–October 1992, are given. With the help of the solar disk-darkening coefficients, the solar flux values at 1 AU are available. The measured 1-nm integrals were used for the high-resolution solar spectral atlas calibration in order to locate the solar continuum in absolute units. A comparison is made of the data obtained with the data by Neckel and Labs (1984) and data of some other authors.     

CCD Observations of Comet Hale-Bopp at Shajn Telescope I. Coude spectra

Spectroscopic observations of Comet Hale-Bopp were made at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory. Some spectra were obtained with high spectral resolution, FWHM = 0.18–0.4Å, in the coude focus on February 22 and 26, 1997. The observations were made in selected spectral windows (4805–4872 Å,6528–6595 Å, 7186–7253 Å, 8276–8408 Å).The spectrograph slit was centered on the nucleus and had dimensions of 25.2 × 0.6 arcsec² on the plane of the sky. The continuum spatial profiles were extremely asymmetrical toward the Sun. However, the continuum-subtracted spatial profiles of the molecular emissions were symmetrical relative to the nucleus, except for C₂. The shape of the spatial profiles of the C₂ emissions is similar to that one of continuum but is more flattened. So, there are evidences that dust can be an additional source of the C₂ radicals in the cometary coma. The main aim of our research was identification of the cometary emissions. Using recent laboratory spectroscopic data we identified newlines of C₂ associated with the transitions from high rotational levels in the 4805–4872 Å spectral region. We detected cometary H_α emission as well. Emissions of NH₂, H₂O⁺,and C₂ (Phillips system) were found in the red spectral windows. Some emission features are still unassigned.     

Peculiarities in the formation of complex organic compounds in a nitrogen–methane atmosphere during hypervelocity impacts

Results of the experiments on model impact vaporization of peridotite, a mineral analogue of stony asteroids, in a nitrogen–methane atmosphere are presented. Nd-glass laser (γ = 1.06 µm) was used for simulation. Pulse energy was ~600–700 J, pulse duration ~10^–3 s, vaporization tempereature ~4000–5000 K. The gaseous medium (96% vol. of N₂ and 4% vol. of CH₄, P = 1 atm) was a possible analogue of early atmospheres of terrestrial planets and corresponded to the present-day atmosphere composition of Titan, a satellite of Saturn. By means of pyrolytic gas chromatography/mass spectrometry, it is shown that solid condensates obtained in laser experiments contain relatively complex lowand high-molecular weight (kerogen-like) organic compounds. The main products of condensate pyrolysis were benzene and alkyl benzenes (including long-chain ones), unbranched aliphatic hydrocarbons, and various nitrogen-containing compounds (aliphatic and aromatic nitriles and pyrrol). It is shown that the nitrogen–methane atmosphere favors the formation of complex organic compounds upon hypervelocity impacts with the participation of stony bodies even with a small methane content in it. In this process, falling bodies may not contain carbon, hydrogen, and other chemical elements necessary for the formation of the organic matter. In such conditions, a noticeable contribution to the impact-induced synthesis of complex organic substances is probably made by heterogeneous catalytic reactions, in particular, Fischer–Tropsch type reactions.