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Boris Zhilyaev

Main Astronomical Observatory, Laboratory for Transient Phenomena in Variable Stars, Head of Laboratory

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Asteroid 14346 Zhilyaev (1985 QG5)D.Sc. Boris E. Zhilyaev e-mail: zhilyaev@mao.kiev.ua tel: 380 (98) 4177108 fax: 380 (44) 5262147 Main Astronomical Observatory National Academy of Sciences of Ukraine 27 Akademika Zabolotnoho St. 03143 Kyiv, Ukraine 324 room

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Papers by Boris Zhilyaev

Observations and Characteristics of Unidenti ed Aerial Phenomena

by Boris Zhilyaev and Vladimir Petukhov

Observations-and-Characteristics-of-Unidentified-Aerial-Phenomena-pdf, 2025

Context: "Unidenti ed Aerial Phenomena" (UAP) describe aerial objects that cannot be identi ed or... more Context: "Unidenti ed Aerial Phenomena" (UAP) describe aerial objects that cannot be identi ed or explained. ese phenomena have been the subject of signi cant interest, investigation, as governments and scienti c communities. Below is a review of astronomical observations related to UAPs. We emphasize statistical measurements of data that are key ndings for speed, altitude, and size estimation of UAPs. Aims: Monitoring the daytime sky allows us to detect bright and dark objects moving at speeds of several Mach, hundreds of meters in size and more, and to assess their characteristics. Methods: Two meteor stations for two-sided monitoring with a base of up to 120 km were used to detect luminous objects in the troposphere and near space. Observations were made in the visible and infrared regions of the spectrum. Results: We are discovering UAPs showing regular ashes with a duration of hundredths of a second. Two-sided monitoring led to the detection of luminous objects in the troposphere at an altitude of 2.6 km, moving at a speed of 2.3 Mach with a linear size of about 6 meters. Two-sided monitoring of the daytime sky led to the detection of a luminous space object at an altitude of 1,174 km, moving at a speed of 282 km/s, with a linear size exceeding 100 meters. Colourimetry showed a space object that has an albedo comparable to that of the Moon (0.037). If we assume that the object glows with re ected light from the Sun, its size is estimated at 3.0 ± 0.4 km. e UAP was recorded by the Ukrainian armed forces in the combat zone at an estimated altitude of 8 km. Its speed is about 2.5 M. e object has a huge width of about 6 km and a height of about 1.5 km.

Observations and Characteristics of Unidenti ed Aerial Phenomena

Context: "Unidenti ed Aerial Phenomena" (UAP) describe aerial objects that cannot be identi ed or... more Context: "Unidenti ed Aerial Phenomena" (UAP) describe aerial objects that cannot be identi ed or explained. ese phenomena have been the subject of signi cant interest, investigation, as governments and scienti c communities. Below is a review of astronomical observations related to UAPs. We emphasize statistical measurements of data that are key ndings for speed, altitude, and size estimation of UAPs. Aims: Monitoring the daytime sky allows us to detect bright and dark objects moving at speeds of several Mach, hundreds of meters in size and more, and to assess their characteristics. Methods: Two meteor stations for two-sided monitoring with a base of up to 120 km were used to detect luminous objects in the troposphere and near space. Observations were made in the visible and infrared regions of the spectrum. We are discovering UAPs showing regular ashes with a duration of hundredths of a second. Two-sided monitoring led to the detection of luminous objects in the troposphere at an altitude of 2.6 km, moving at a speed of 2.3 Mach with a linear size of about 6 meters. Two-sided monitoring of the daytime sky led to the detection of a luminous space object at an altitude of 1,174 km, moving at a speed of 282 km/s, with a linear size exceeding 100 meters. Colourimetry showed a space object that has an albedo comparable to that of the Moon (0.037). If we assume that the object glows with re ected light from the Sun, its size is estimated at 3.0 ± 0.4 km. e UAP was recorded by the Ukrainian armed forces in the combat zone at an estimated altitude of 8 km. Its speed is about 2.5 M. e object has a huge width of about 6 km and a height of about 1.5 km.

Unidentified Aerial Phenomena. Overview of Observations and Characterization Estimation

preprint, 2025

We use high-tech observations of Unidentified Aerial Phenomena (UAP) class objects to evaluate th... more We use high-tech observations of Unidentified Aerial Phenomena (UAP) class objects to evaluate their characteristics. We present data in five cases. (1) Bright UAPs over Kyiv and San Diego. (2) Dark objects over Kyiv and New York. (3) Space UAPs. (4) Analysis of objects near the Moon. (5) Analysis of the object recorded in the combat zone. Two-side observations of bright UAPs showed tropospheric objects at altitudes of several kilometers, size is about 10 m and speed of several Mach or more. Two-side space UAP observations showed objects at altitudes of more than 1000 km that exhibit unprecedentedly high linear velocities of hundreds of km/s and sizes of several kilometers. UAP observations over Kiev and New York revealed objects of large linear size, one about 150 meters and the other about 100 meters, with unprecedentedly high speeds, about 120 km/s and the other about 13 km/s. The motion of the objects does not cause atmospheric disturbances. We report sightings of objects of enormous size. They resemble a large floating island in the sky, similar to Laputa, described in Swift's novel "Gulliver". The albedo of these objects is a few percent, making their detection a challenge.

Unidentified Aerial Phenomena. Characterization of Dark UAPs

DOI: 10.13140/RG.2.2.32223.78243, 2025

We use high-tech observations of Unidentified Aerial Phenomena (UAP) class objects to evaluate th... more We use high-tech observations of Unidentified Aerial Phenomena (UAP) class objects to evaluate their characteristics. We present data in three cases. (1) Multi-side daytime observations of UAPs over Kiev. (2) Night observations of a group of objects in the vicinity of the Moon. (3) UAP observations in the combat zone in Ukraine. Dark UAPs in the visible wavelength range are observed only during the day. At night they can only be seen in the infrared wavelength range. We note large sizes of UAPs, from three to six kilometers.They exhibit large velocities, from 2.5 Mach and much larger. They have low albedo, from three percent and below, that is, they actually exhibit features of a completely black body.

Small-scale variability in the spectrum of Vega

preprint, 2025

We reported the results of observations of small-scale variability in the hydrogen Balmer lines i... more We reported the results of observations of small-scale variability in the hydrogen Balmer lines in Vega. Spectral observations were carried out with low-resolution spectrograph (R ≃ 600) installed in the Main Astronomical Observatory, Ukraine. Spectra were obtained with a time resolution in the second range. It has been found that Vega shows variations in the hydrogen lines H β , Hγ, H δ. This can be interpreted that their variations are non-radial pulsations. The characteristic time of the observed variations ranges from 300 to 1200 sec. The horizontal scale for oscillating elements is about 800 Mm, which is comparable to the solar radius. The radial velocity of the variations is about 36 km/s.

Diagnostics of small-scale details on asteroid’s surface from the fast spectrophotometry data

Kinematics and Physics of Celestial Bodies, Sep 1, 2016

Fast spectrophotometry of the flare star EV lacertae

Astronomy Letters, Dec 1, 2012

We present the results of fast spectrophotometry for two flares on EV Lac with a time resolution ... more We present the results of fast spectrophotometry for two flares on EV Lac with a time resolution of 8 s and a spectroscopic resolution R ∼ 100. The observations were performed in May and August 2010 with a slitless spectrograph on the Zeiss-600 telescope at Peak Terskol. We have estimated the U BV R magnitudes from spectrograms through a mathematical convolution of the spectra with the filter transmission curves. The U BV R amplitudes of the August 10, 2010 flare are 2 m . 83, 1 m . 94, 0 m . 82, and 0 m . 28, respectively. The U BV R amplitudes of the May 30, 2010 flare are 0 m . 65, 0 m . 25, 0 m . 15, and 0 m . 10, respectively. A detailed colorimetric analysis has allowed important parameters of the flares on EV Lac to be estimated: the temperatures at maximum light and their sizes. The color-color (U -B)-(B -V ) diagrams confirm that both flares at maximum light radiate as a blackbody. The temperatures at maximum light was 13 400 ± 500 K for the August flare and 5700 ± 100 K for the May flare. During the May flare, an additional hydrogen emission appeared in the Balmer Hα, Hβ, Hγ, Hδ, H , Hζ lines and the Balmer continuum (3647 Å) in the spectrum of EV Lac. The excess of emission in the Balmer lines was approximately from two to thirty percent. Based on our colorimetric analysis, we have estimated the linear sizes of the flares at maximum light. The size of the May 30, 2010 flare is approximately 7% of the stellar radius. The size of the August 10, 2010 flare is 3.9% of the stellar radius.

High-frequency variations of spectral lines in cromospherically active stars 61 cyg AB

Kinematics and Physics of Celestial Bodies, Nov 1, 2015

We report on the detection of rapid variability in subsecond mode in the Balmer lines of hydrogen... more We report on the detection of rapid variability in subsecond mode in the Balmer lines of hydrogen, lines Ca II H,K, and b Mg I triplet in chromospherically active stars 61 Cyg A, B. The spec tral observations of 61 Cyg A, B were performed with MMCS spectrograph in Cassegrain's focus of the 2 m telescope at peak Terskol (R = 13000), with a grating spectrograph mounted on a 60 cm telescope at peak Terskol (R ≈ 100), and a 60 cm telescope of the Andrushivka Observatory (R ≈ 200). The obser vations were carried out in the framework of international campaign of observations of variable stars using the Synchronous Network of Telescopes. The high resolution spectra were obtained with inter vals of approximately 2 minutes. The low resolution spectra were obtained with intervals from 2 to 3 seconds. Spectral monitoring lasted from 30 minutes to 2 hours. We found that chromospherically active dwarf stars 61 Cyg A, B, having extensional spots on their surfaces exhibit rapid variations in the hydrogen lines, lines CaII H, K of ionized calcium and chromospheric triplet b Mg I on a time scale from approximately 2 seconds to approximately 2 minutes. Variations in the intensity of lines range from 1.5% in the Balmer series of hydrogen to approximately 0.5% in the lines of b Mg I triplet. These variations are well described by the shot noise model in the form of random elementary pulses with the frequency of occurrence of a few fractions of events per second to a few events per second. Comparison of rapid variations in chromospheric lines with different time intervals demonstrates the transient nature of this activity both on short (subsecond) and long time scales.

Unidentified aerial phenomena. Observations of night events

The 2022 Pentagon Unidentified Aerial Phenomena (UAP) Report covers 510 catalogued UAP reports co... more The 2022 Pentagon Unidentified Aerial Phenomena (UAP) Report covers 510 catalogued UAP reports collected by branches of the U.S. military. "The 171 reports demonstrated unusual flight characteristics and require further analysis,"-the report said. NASA commissioned a research team to study UAP, observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. We analyze UAP's nighttime observations posted to Instagram on 24-2-2024. The British newspaper Daily Mail wrote about this sighting under the headline "Ukrainian Armed Forces record disc-shaped UFO in war zone". The object was discovered by chance during a nighttime drone inspection at 6.1 degrees above the horizon. It was initially located 88 km away, at an altitude of 8 km. During an observation time of 17 seconds, it flew 14 km at a speed of 803 m/s (Mach 2.5). The object is Disk-shaped and of considerable size.

Unidentified Aerial Phenomena. Heaven Battle

The Unidentified Aerial Phenomena (UAP) or Unidentified Flying Objects (UFO) objects collected in... more The Unidentified Aerial Phenomena (UAP) or Unidentified Flying Objects (UFO) objects collected in the main by branches of the U.S. military. Most were assessed as routine airborne phenomena. The remaining demonstrated unusual flight characteristics and required further analysis. Thus, UFOs as pop culture objects have become objects of scientific research. NASA and the Harvard University Observatory are engaged in UAP research. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP. Here we consider an episode involving two UAP objects. The episode was observed on April 23, 2018, in Kyiv and lasted about 3 sec. The speed of the objects is supersonic, about 3 M.

Unidentified Aerial Phenomena I. Observations and Characterizations of Events

The 2022 Pentagon Unidentified Aerial Phenomena (UAP) or Unidentified Flying Objects (UFO) Report... more The 2022 Pentagon Unidentified Aerial Phenomena (UAP) or Unidentified Flying Objects (UFO) Report covers approximately 510 catalogued UAP reports collected by branches of the U.S. military. "The 366 reports were assessed as routine airborne phenomena. The remaining 171 reports demonstrated unusual flight characteristics and require further analysis," the report said. Thus, UFOs as pop culture objects have become objects of scientific research. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP. For observations we used two meteor stations installed in Kyiv and the Vinarivka village south of the Kyiv region at a base of 120 km. Two-side monitoring led to the detection of luminous object in the troposphere at an altitude of 2.6 km, moving at a speed of 2.3 Mach with a linear size of about 6 meters. Two-side monitoring of the daytime sky led to the detection of luminous space object at an altitude of 1174 km, moving at a speed of 282 km/s, with a linear size of more than 100 meters. We have drawn a meaningful conclusion from observations of space UAPs. They are observed on a time interval in the sub second range. They demonstrate unprecedented high velocities and high-frequency brightness variability. The detection of these objects is an experimental fact. Estimates of their characteristics follow from observational data. The authors do not interpret these objects.

Unidentified aerial phenomena. Observations of variable objects

arXiv (Cornell University), Jun 11, 2023

NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP). The Main Astronom... more NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP). The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP. A research team from San Diego also decided to conduct a study of UAP. Observations of events that cannot scientifically be identified as known natural phenomena established the existence of the UAP. However, their nature remains unclear. For UAP observations, we used a meteor station installed in Kyiv. We also present a new methodology for detecting UAPs using the latest smartphone technology in San Diego. We inform about discovering a new type of UAP.

Unidentified aerial phenomena. Observations of space objects

arXiv:submit/5386311 [astro-ph.IM] 2 Feb 2024

NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of e... more NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. For UAP observations, we used two meteor stations installed in Kyiv and in the Vinarivka village in the south of the Kyiv region. Two-side monitoring of the daytime sky led to the detection of three luminous objects at an altitude of 620, 1130 and 1174 km, moving at a speed of 256, 78 and 282 km/s. We have drawn a meaningful conclusion from observations of space UAPs. They appear and disappear suddenly, and are observed on a time interval in the subsecond range. At the same time, they demonstrate unprecedented high velocities and highfrequency brightness variability. The detection of these objects is an experimental fact. Estimates of their characteristics follow from observational data. The authors do not interpret these objects.

Unidentified aerial phenomena. UAPs over Kyiv

preprint

NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of e... more NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. For UAP observations, we used a meteor station installed in Kyiv. We have identified three groups of objects (1) a group of bright spinning objects, (2) a group of bright structured objects and (3) a group of dark flying objects. Monitoring of the daytime sky led to the detection of bright and dark objects, moving at a speed from about 1M to 16M and sizes from about 20 to 100 meters. The detection of these objects is an experimental fact. Estimates of their characteristics follow from observational data. The authors do not interpret these objects.

Unidentified Aerial Phenomena. Events over Kyiv and New York

by Boris Zhilyaev and Dan Caron

arXiv:submit/5381093 [astro-ph.IM] 31 Jan 2024

We present observations of objects of the Unidentified Aerial Phenomena (UAP) class in Kyiv and N... more We present observations of objects of the Unidentified Aerial Phenomena (UAP) class in Kyiv and New York. Both events are short-lived, 0.17 and 1.028 seconds. Both objects have large linear dimensions, about 150 meters, and the other is about 100 meters. Both objects have an unprecedentedly high speed, about 120 km/s and the other is about 13 km/s.

Unidentified aerial phenomena. Observations of variable objects

arXiv:2306.13664v1 [physics.pop-ph] 11 Jun 2023, 2023

NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP). The Main Astronom... more NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP). The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP. A research team from San Diego also decided to conduct a study of UAP. Observations of events that cannot scientifically be identified as known natural phenomena established the existence of the UAP. However, their nature remains unclear. For UAP observations, we used a meteor station installed in Kyiv. We also present a new methodology for detecting UAPs using the latest smartphone technology in San Diego. We inform about discovering a new type of UAP.

Unidentified aerial phenomena II. Evaluation of UAP properties

NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of e... more NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. For UAP observations, we used two meteor stations installed in Kyiv and in the Vinarivka village in the south of the Kyiv region. Two-side monitoring of the daytime sky led to the detection of two luminous objects at an altitude of 620 and 1130 km, moving at a speed of 256 and 78 km/s. Colorimetric analysis showed that the objects are dark: B-V = 1.35, V-R = 0.23. The size of objects is estimated to be more than 100 meters. The detection of these objects is an experimental fact. Estimates of their characteristics follow from observational data. The authors do not interpret these objects. Daytime sky monitoring in Kyiv with multi-color DSLR camera at a rate of 30 frames per second in August and September 2018 and in Vinarivka with a multi-color CMOS camera in October 2022 revealed several cases of dark objects (phantoms). The time of their existence is, as a rule, a fraction of a second. These are oval-shaped objects ranging in size from 20 to 100 meters with speeds from 2 to 30 km/s.

Creation of the Ukrainian meteor observation network: instruments, methods for processing, observatin possibilities

Kosmìčna nauka ì tehnologìâ

The development of meteor astronomy in modern Ukraine is considered. The specificity of meteor ob... more The development of meteor astronomy in modern Ukraine is considered. The specificity of meteor observation methods requires, first of all, the organization of a network of corresponding observation points. To achieve this goal, it is proposed to combine the scientific and technical capabilities of participating organizations in the form of the Ukrainian Meteor Observation Network (UMON). UMON is a set of two or more permanent observation stations located on the territory of Ukraine, which have the hardware and software for basic and one-sided observations of meteors in different wavelength ranges and conduct such observations. UMON aims to solve important problems of meteor research, structure and evolution of meteor streams and showers, the interaction of meteoroids with the Earth’s atmosphere and their chemical composition. The scientific and technical products of UMON stations are the results of high-precision basic or one-sided observations of meteors in different wavelength ran...

Unidentified aerial phenomena I. Observations of events

arXiv (Cornell University), Aug 23, 2022

NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of e... more NASA commissioned a research team to study Unidentified Aerial Phenomena (UAP), observations of events that cannot scientifically be identified as known natural phenomena. The Main Astronomical Observatory of NAS of Ukraine conducts an independent study of UAP also. For UAP observations, we used two meteor stations installed in Kyiv and in the Vinarivka village in the south of the Kyiv region. Observations were performed with colour video cameras in the daytime sky. We have developed a special observation technique, for detecting and evaluating UAP characteristics. According to our data, there are two types of UAP, which we conventionally call: (1) Cosmics, and (2) Phantoms. We note that Cosmics are luminous objects, brighter than the background of the sky. We call these ships names of birds (swift, falcon, eagle). Phantoms are dark objects, with contrast from several to about 50 per cent. We present a broad range of UAPs. We see them everywhere. We observe a significant number of objects whose nature is not clear. Flights of single, group and squadrons of the ships were detected, moving at speeds from 3 to 15 degrees per second. Some bright objects exhibit regular brightness variability in the range of 10-20 Hz. Two-site observations of UAPs at a base of 120 km with two synchronised cameras allowed the detection of a variable object, at an altitude of 1170 km. It flashes for one hundredth of a second at an average of 20 Hz. We use colourimetry methods to determine of distance to objects and evaluate their color characteristics. Objects RGB colors of the Adobe color system had converted to the Johnson BVR astronomical color system using the color corrections. Phantom shows the colur characteristics inherent in an object with zero albedos. It is a completely black body that does not emit and absorbs all the radiation falling on it. We see an object because it shields radiation due to Rayleigh scattering. An object contrast makes it possible to estimate the distance using colorimetric methods. Phantoms are observed in the troposphere at distances up to 10-12 km. We estimate their size from 3 to 12 meters and speeds up to 15 km/s.

Diagnostics of small-scale details on asteroid’s surface from the fast spectrophotometry data

Kinematics and Physics of Celestial Bodies, 2016

To study the mineralogical composition of an asteroid's surface with a technique of colorimetry o... more To study the mineralogical composition of an asteroid's surface with a technique of colorimetry of small-scale details, we propose fast spectrophotometry with a low-resolution imaging spectrograph and a time resolution of a few minutes. In contrast to global tomography, our method allows only the features of small scale, as compared to the asteroid's size, to be detected. As an example, the surface of asteroid 130 Elektra exhibits approximately 16 spots of different mineralogical composition; their sizes range from 13 to 30 km. Except for several cases, the absorption spectra of these features are typical of the olivine-pyroxene compounds. In principle, color characteristics of the spots in the UBVRI color system allow the mineralogical composition of the surface of a small celestial body to be identified.