Terskol Observatory Research Articles

Changes in the longitude polarization dependence of Jupiter's moon Io as evidence of the long-term variability of its volcanic activity

The aim of the work was to investigate the longitude (orbital) dependence of the polarization of Jupiter's moon Io and compare results of our study with what is reported in the literature. We used our published observations and supplemented them with new measurements carried out with the polarimeters mounted on the 2.6 m Shajn telescope of the Crimean Astrophysical Observatory and the 2 m telescope of the Peak Terskol Observatory in the UBVRI bands at phase angles between 10° and 12° in August 2023 – February 2024. We have determined that amplitude of the orbital polarization in the V band does not exceed ≈0.1 %. It is the deepest −0.17 ± 0.03 % at L ≈ 270° and the shallowest −0.07 ± 0.03 % near L ≈ 130°. These parameters differ markedly from that obtained by Zellner and Gradie (1975), which found that the orbital polarization variations from 0.4 to 0.5 % for α > 10°, and the negative branch is the deepest near L = 160° and the shallowest near L = 300°. These differences may be a consequence of changes in the reflective properties of the local areas of Io's surface due to long-term changes in Io's local or global volcanic activity.

Vertical Distribution of Optical Turbulence at the Peak Terskol Observatory and Mount Kurapdag

Atmospheric turbulence characteristics are essential in determining the quality of astronomical images and implementing adaptive optics systems. In this study, the vertical distributions of optical turbulence at the Peak Terskol observatory (43.27472°N 42.50083°E, 3127 m a.s.l.) using the Era-5 reanalysis and scintillation measurements are investigated. For the closest reanalysis grid node to the observatory, vertical profiles of the structural constant of the air refractive index turbulent fluctuations Cn2 were obtained. The calculated Cn2(z) vertical profiles are compared with the vertical distribution of turbulence intensity obtained from tomographic measurements with a Shack–Hartmann sensor. The atmospheric coherence length at the location of Terskol Peak was estimated. Using a combination of atmospheric models and paramaterization schemes of turbulence, Cn2(z) profiles at Mt. Kurapdag were obtained. The values of atmospheric coherence length at Peak Terskol are compared with estimated values of this length at the ten astronomical sites, including Ali, Lenghu and Daocheng.

New Polarimetric Data for the Galilean Satellites: Io and Ganymede Observations and Modeling

New high-precision disk-integrated measurements of the polarization of Io and Ganymede in the UBVRI bands are presented. The observations were obtained using polarimeters mounted on the Crimean Astrophysical Observatory and the Peak Terskol Observatory in 2019–2023. For Io, the negative polarization branch (NPB) reaches a minimum of P min ≈ −0.25 ± 0.02% in the V band at a phase angle of α min = 2.°1 ± 0.°5. The inversion angle is α inv = 26° ± 6° in the V and R bands. The NPB for Ganymede is an asymmetric curve, with P min = −0.34 ± 0.01% at α min = 0.°52 ± 0.°06 and α inv = 8.°5 ± 0.°2 in the V band. Although Io and Europa have similar geometric albedos (0.63 and 0.67, respectively), their NPB shapes differ. The NPB of Ganymede (albedo of 0.43) is morphologically similar to that of Europa, although it is described by different parameter values (P min, α min, and α inv). This discrepancy is likely due to the compositions of their surfaces: Europa’s with H2O ice, Io’s with sulfuric/silicate composition, and Ganymede’s with H2O ice and silicates. Numerical computations using the radiative transfer coherent backscattering method demonstrated a match to the polarimetric observations and to the geometric albedos for Ganymede with the single-scattering albedo ≈ 0.943 and mean free path length kl = 2πl/λ eff ≈ 150, where λ eff is the wavelength. For Io’s regolith, the single-scattering albedo was found to be ≈ 0.979 and kl ≈ 40.

Erratum to: Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

Erratum to: Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

Observations and study of the orbital dynamics of some near-Sun asteroids

The paper presents the results of positional observations of nine near-Sun asteroids with the Zeiss-2000 telescope at the Center for Collective Use “Terskol Observatory” during 2020–2023. It demonstrates that, under favorable weather conditions, it is possible to obtain observations of asteroids with observed magnitudes up to 22. Particular attention is paid to the objects (399457) 2002 PD43 and 2008 MG1. We managed to obtain observations of (399457) 2002 PD43 at an observed magnitude of 21.6m, making our observations the first of the summer 2022 opposition. The results of the orbit fitting and the study of the probabilistic orbital evolution of 2008 MG1 are considered separately, since the observations at the Terskol observatory significantly extend its arc length and reduce the orbit uncertainty.

Results of polarimetric and photometric observations of NEAs 162082 (1998 HL1), 163373 (2002 PZ39), 52768 (1982 OR2), and 159402 (1999 AP10)

ABSTRACT We present the results of polarimetric and photometric observations of four near-Earth asteroids (NEAs) 162082 (1998 HL1), 163373 (2002 PZ39), 52768 (1982 OR2), and 159402 (1999 AP10). The observations were carried out at the 2.6-m and 1.25-m telescopes of the Crimean Astrophysical Observatory, the 2.0-m telescope of the Peak Terskol Observatory, and the 6-m telescope of the Special Astrophysical Observatory during the period of 2019–2020. The phase angles covered in the observations were 3°–27°, 69°–109°, 70°–76°, and 32°–72° for NEAs 162082, 163373, 52768, and 159402, respectively. We estimated the main polarimetric parameters of the phase curves for each asteroid. The geometrical albedo for NEAs 162082, 163373, and 159402 were found to be 0.348 ± 0.050, 0.192 ± 0.050, and 0.124 ± 0.020, respectively. The diameters for asteroids 162082, 163373, 52768, and 159402 were determined as 0.37 ± 0.05, 0.50 ± 0.05, 2.61 ± 0.20, and 2.27 ± 0.20 km, respectively. The polarization data for NEA 52768 and 159402 are similar. Their orbital elements a, e, q, and periods for these asteroids also showed close similarities, indicating a potential common parent body in the past. We found deviation of the polarization of NEAs 163373, 52768, and 159402 from the synthetic phase dependences of the polarization of the main taxonomic С, S, and E classes. To explain this, the modified Sh-matrix method was used. The computer simulation has shown that different values of the maximum of positive polarization of asteroids can be explained by different content of highly absorbing carbon matter.

Long-Term Trends of Astroclimatic Parameters above the Terskol Observatory

Astroclimatic conditions characterize the quality of an astronomical site. The Terskol Observatory was founded over 42 years ago in 1980. The astronomical site (coordinates 43°16′29″ N, 42°30′03″ E) is located about 10 km from Mt. Elbrus in the northern Caucasus Mountains. The paper presents the results of an analysis of long-term variations from 1980 to 2022 of astroclimatic parameters such as total cloud cover, precipitable water vapor, and wind speed at a level of 200 hPa above the Terskol Observatory using atmospheric ERA5 Reanalysis data from the European Center for Medium-Range Weather Forecast. The probability distributions and seasonal variations of the astroclimatic parameters are also presented. Long-term trends of the astroclimatic parameters are studied with statistically significant trend analysis methods using the Mann–Kendall test and the Sen’s slope test to estimate the magnitude of the changes. The results show non-significant decreases of annual average 200-hPa wind speed and increases in precipitable water vapor, but significant (99 per cent confidence level) long-term decreasing of total cloud cover above the Terskol Observatory.

Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

The paper presents a method for processing positional observations of near-Earth objects using a numerical model of satellite motion developed at the Research Institute of Applied Mathematics and Mechanics of Tomsk State University (NII PMM TSU). The root-mean-square error of orbit improvement without rejection of observations for such objects does not exceed 0.3″ over a seven-day time interval. The results of the presentation of observations for the next occurrence of the object are obtained, which makes it possible to find the object in a time interval of five months. The orbit has been refined in the joint processing of measurements on several occurrences of the object over a six-month time interval. All results were obtained from observations made on the equipment of the Terskol Observatory Shared Use Center.

SEASON VARIATIONS OF ASTROCLIMATE PARAMETERS FOR THE TERSKOL OBSERVATORY

We present results of the study of seasonal variations of the astroclimate parameters for the Terskol Observatory: wind speed at the level of 200 mbar as a measure of the adaptive optics (AO) applicability, the wind speed altitude distribution, determining the requirements for the AO performance, moisture content to assess the possibility of AO operation in the IR range, the parameters of the mesospheric sodium layer, determining the brightness of the laser reference star for AO systems, in connection with the task of designing adaptive optics for the Zeiss-2000 telescope. Data on surface wind speed and total cloud cover are also analyzed to assess the available observation time. The data of atmospheric reanalysis were used, with the help of which the parameters under consideration have been studied in large astronomical observatories, as well as satellite data of measurements of mesospheric sodium and full-scale changes in surface wind velocity.

Quasi-simultaneous photometric, polarimetric, and spectral observations of distant comet C/2014 B1 (Schwartz)

Context. We analyze the results of our comprehensive observations of the high-perihelion comet C/2014 B1 (Schwartz) with stable disk-shaped coma and jets in order to study its nature. Aims. The main objective of our study is to obtain new observational results for a unique disk-like comet C/2014 B1 (Schwartz) with a perihelion distance of 9.56 au. Methods. Quasi-simultaneous long-slit spectra, as well as photometric and polarimetric images with g-sdss and r-sdss filters, were acquired with the 6 m telescope of the Special Astrophysical Observatory on 2017 January 23. The BVR-band photometry of the comet was also performed at the 2m telescope of the Peak Terskol Observatory on 2017 January 31. We modeled the dynamics of the jets and the behavior of the color and polarization in the coma considering the dust as aggregated large particles. Results. We did not reveal any emissions in the spectra. The positions of two jets oriented along the position angles of 179° and 350° and the disk-like shape of the coma have remained unchanged for more than 4 yr. The most realistic model able to explain jets of such stable orientation includes the existence of two active sources located near the north and south poles of the rotating nucleus whose diameter was determined to be between 7.6 and 12.2 km depending on the albedo, of namely between 0.1 and 0.04, respectively. The high activity of the comet is characterized by the high dust production Afρ which varied from 4440 to 3357 cm between 2017 January 23 and 31. A significant difference between the radial surface brightness profiles of the jets and the ambient (undisturbed by the jets) coma is found. The color of the jet structures is much redder than that of the ambient coma, and the nucleus has a very red color, V − R=0.93m±0.19m. There are spatial variations of the color and polarization over the coma and jets. Conclusions. The observed trends in color and polarization, as well as the brightness profiles, can be explained by the fragmentation of aggregated particles formed by CO2/H2O ices, silicates, and organics, which are of ~1 mm in radius near the nucleus and ~10 μm in radius at the periphery of the coma.

Aperture polarimetry of selected comets in 2018–2020: Observations and computer simulation

Polarimetric studies are an important source of information about the physical properties of celestial bodies. In 2018, we put into operation the new two-channel polarimeters in the Crimean Astrophysical Observatory and the Peak Terskol Observatory. With the help of these instruments, in the period from 2018 to 2020, we carried out measurements of the polarization characteristics of 19 comets. Based on these data, we obtained the phase dependences of linear polarization degree of comets in the R, V, and I broadband filters. We approximate the polarization curves by a trigonometric expression. It was found that in the region of negative polarization, the phase curves of polarization in all three filters practically coincide. We also found that there is a noticeable difference in the degree of linear polarization between short-period and long-period comets. The polarization minimum of short-period comets is almost twice as high as that of long-period comets. It is shown, that for the interpretation of observational data, multispectral observations in at least three different spectral ranges are required. Moreover, for a reliable interpretation of observations, model particles with internal porosity should be used.

New Polarimetric Data for the Galilean Satellites: Europa Observations and Modeling

This paper is dedicated to a long-standing problem of the shape of the negative branch of polarization (NBP) for Jupiter's moon Europa, determination of which is crucial for the characterization of the icy regolith on this satellite and similar objects, as well as for further progress in understanding light scattering by particulate surfaces. To establish the shape of Europa's NBP, in 2018–2021 we accomplished high-precision disk-integrated polarimetry of Europa in the UBVR I bands using the identical two-channel photoelectric polarimeters mounted on the 2.6 m Shajn reflector of the Crimean Astrophysical Observatory and the 2 m telescope of the Peak Terskol Observatory. We found that the polarization dependence on the phase angle in each filter is an asymmetric curve with a sharp polarization minimum at phase angle , after which the polarization degree gradually increases to positive values, passing the inversion angle at α inv ≈ 6° − 7°. Within the error limits, the parameters P min, , and α inv of the NPB are independent of the wavelength in the visible spectrum. The polarization curve clearly demonstrates the so-called polarization opposition effect (POE). Our analysis of the previous and new polarimetric observations of Europa allows us to conclude that the POE is caused by coherent backscattering of sunlight on microscopic icy grains covering Europa’s surface. Computer modeling with the numerical radiative transfer coherent backscattering method demonstrates that the best fit to the polarimetric observations and geometric albedo of Europa is provided by a regolith layer of elementary single-scattering albedo ∼0.985 and extinction mean free path length 2π l/λ eff ≈ 150, λ eff representing the effective wavelength in the UBVR I spectral bands.

Small Solar System objects on highly inclined orbits

Context. Less than one percent of the discovered small Solar System objects have highly inclined orbits (i > 60°), and revolve around the Sun on near-polar or retrograde orbits. The origin and evolutionary history of these objects are not yet clear. Aims. In this work we study the surface properties and orbital dynamics of selected high-inclination objects. Methods. BVRI photometric observations were performed in 2019–2020 using the 2.0 m telescope at the Terskol Observatory and the 2.6 m telescope at the Crimean Astrophysical Observatory. Additionally, we searched for high-inclination objects in the Sloan Digital Sky Survey and Pan-STARRS. The dynamics of the selected objects was studied using numerical simulations. Results. We obtained new photometric observations of six high-inclination objects (468861) 2013 LU28, (517717) 2015 KZ120, 2020 EP, A/2019 U5 (A/PanSTARRS), C/2018 DO4 (Lemmon), and C/2019 O3 (Palomar). All of the objects have similar B−V, V −R, R−I colours, which are close to those of moderately red TNOs and grey Centaurs. The photometric data that were extracted from the all-sky surveys also correspond to moderately red surfaces of high-inclination objects. No signs of ultra-red material on the surface of high-inclination asteroids were found, which supports the results of previous works. The comet C/2018 DO4 (Lemmon) revealed some complex morphology with structures that could be associated with particles that were ejected from the cometary nucleus. Its value of the parameter Afρ is around 100 cm for the aperture size of 6000 km. The value of Afρ for the hyperbolic comet C/2019 O3 (Palomar) is much larger, and is in the range from 2000 to 3700 cm for the aperture sizes from 25 000 to 60 000 km. For objects 2013 LU28, 2015 KZ120, and 2020 EP we estimated future and past lifetimes on their orbits. It appears that the orbits of considered objects are strongly chaotic, and with the available accuracy of the orbital elements no reliable predictions can be made about their distant past or future. The lifetimes of high-inclination objects turned out to be highly non-sensitive to the precision of the orbital elements, and to the Yarkovsky orbital drift.

Search for Ultrafast Variability of Line Profiles in the Spectrum of ε Per A

The results of observations at high temporal resolution (∆T~4 min) of the B0.5V star e Per A on the 2-m telescope of the Terskol Observatory are reported. Regular components of variations in line profiles with periods 1.5-18 hours are recorded. Evidence of irregular variations in line profiles on time scales of minutes is detected. The nature of these variations is discussed.

Spectrophotometric Studies of Near-Earth and Main-Belt Asteroids

The reflectance spectra of five near-Earth asteroids, one Mars crosser, and four classical asteroids of the main belt in the range 0.35–0.95 µm have been observed, calculated, and analyzed. Asteroids with a magnitude up to 17 were observed in 2013–2017 with a 2-m telescope with a CCD spectrograph with extremely low spectral resolution (R ∼ 100) of the Terskol Observatory of the Institute of Astronomy of the Russian Academy of Sciences in order to determine their taxonomic types and composition. These results show that the composition of some of the studied near-Earth asteroids is heterogeneous judging by the variations in their reflectance spectra within adjacent taxonomic classes. It is notable that some of these asteroids are binary. The physical and chemical-mineralogical interpretation of reflectance spectra is presented.

Characteristics of new space debris objects detected at the Terskol observatory

Characteristics of new space debris objects detected at the Terskol observatory

Interstellar Lines and Diffuse Bands in the Spectrum of the Supergiant κ Cas

We have studied the interstellar lines and diffuse bands in the spectrum of the supergiant κ Cas using the CCD spectra obtained with the Echelle spectrograph of the 2 meter telescope at the peak Terskol observatory. A synthetic stellar spectrum was used to correctly reveal the interstellar features, computed for a model atmosphere with Teff = 21 500 K, log g = 2.60, v sin i = 83 kms-1, [M/H] = 0.0, ξ = 15 kms-1 and with partial selection of main chemical element abundances. Eleven interstellar bands and 91 diffuse interstellar bands were identified. A further 14 absorption features were revealed, possibly also diffuse bands. The spectrophotometric diffuse band parameters and their accuracies were tabulated. We present maps of observed and synthetic spectral regions containing interstellar diffuse bands.

Characteristics of small-sized space debris objects detected at the Terskol observatory in 2016-2017

Abstract The study of near-Earth space includes the detection and investigation of an increasing number of space debris objects by ground-based optical telescopes. There is no natural cleansing of space in the geostationary region. The telescope Zeiss-2000 with a two-meter aperture of the Terskol observatory is the largest optical instrument regularly used for space debris investigations. One of the main purposes in «Astronomy in the Elbrus region» international program’s boundaries is the detection and characterization of small fragments of debris,which are invisible for smaller telescopes. During observations on photometric nights we usually detect 4-5 unknown fragments of 17-21st star magnitude. In this article, we present orbital parameters and physical characteristics of several small-sized fragments of the space debris detected at the Terskol observatory in 2016-2017.

Follow-up studies of Gaia transients at the Terskol Observatory

AbstractSince 2015, scientific activities at the Terskol Observatory have been aimed at optical follow-up of stellar objects and asteroids detected within the framework of the Gaia mission. Two years of successful research have yielded new data and findings in this field. Photometric observations of Gaia transients allowed us to reveal physical characteristics of a good few of them. Moreover, we detected positions of dozens of asteroids which were reported by the GBOT group. In this paper, some results obtained from observations of transients Gaia16bkf, Gaia16bkn, Gaia17asz and newly detected asteroids are presented.