Molecular oxygen(O2)is essential to human beings on the earth.Although elemental oxygen is rather abundant,O2 is rare in the interstellar medium.It was only detected in two galactic and one extra-galactic region.The i...Molecular oxygen(O2)is essential to human beings on the earth.Although elemental oxygen is rather abundant,O2 is rare in the interstellar medium.It was only detected in two galactic and one extra-galactic region.The inconsistency between observations and theoretical studies is a big challenge for astrochemical models.Here we report a two-phase modeling research of molecular oxygen,using the Nautilus gas-grain code.We apply the isothermal cold dense models in the interstellar medium with two typical sets of initial elemental abundances,as well as the warm-up models with various physical conditions.Under cold dense conditions,we nd that the timescales for gas-phase CO,O2 and H2O to reach peak values are dependent on the hydrogen density and are shortened when hydrogen density increases.In warm-up models,O2 abundances are in good agreement with observations at temperatures rising after 10^5 yr.In both isothermal and warm-up models,the steady-state O2 fractional abundance is independent of the hydrogen density,as long as the temperature is high enough(>30 K),at which O2 is prevented from signi cant depleting onto grain surface.In addition,low density is preferable for the formation of O2,whether molecular oxygen is under cold conditions or in warm regions.展开更多
Magnetic fields appear to be ubiquitous in the astrophysical environments of our Universe,but are still poorly understood despite playing an important role in understanding different-scale celestial objects(e.g.,Earth...Magnetic fields appear to be ubiquitous in the astrophysical environments of our Universe,but are still poorly understood despite playing an important role in understanding different-scale celestial objects(e.g.,Earth,planets,stars,normal galaxies,active galactic nuclei,clusters etc.).We briefly review the results and progress in magnetic field estimation based on rotation measures from the large-scale interstellar medium,megaparsec-scale radio jets to the plasma near the black-hole horizon.We find that there is no evident correlation between electron density and magnetic field in warm ionized plasma,which suggests that the estimation of the magnetic field from the ratio of the rotation measure and dispersion measure correctly reflects the intrinsic field.The estimation of the magnetic field from the rotation measure is also discussed near the black hole horizon in M 87.The Square Kilometre Array will greatly improve the understanding of the magnetic field in our Universe,which will provide high-quality polarization imaging and extragalactic rotation measures in the near future.展开更多
By simple arguments, it is shown how alkaline types of atoms can be seen in dense molecular clouds depending on the average temperature of such regions of the Universe. This paper predicts infrared lines of such atoms...By simple arguments, it is shown how alkaline types of atoms can be seen in dense molecular clouds depending on the average temperature of such regions of the Universe. This paper predicts infrared lines of such atoms that could be seen in molecular clouds. The theory is developed in the first part and the predicted experimental results will follow. It results that the alkaline atoms modelized using the short-range polarization potential are found in quantum states <em>n</em><sub>*</sub> > 2.展开更多
Interstellar scattering causes broadening and distortion in the mean pulse profiles and polarization position angle （PPA） curves of pulsars, especially pulse profiles observed at lower frequencies. This paper implem...Interstellar scattering causes broadening and distortion in the mean pulse profiles and polarization position angle （PPA） curves of pulsars, especially pulse profiles observed at lower frequencies. This paper implements a method to recover the pulse profiles and PPA curves of five pulsars which have obvious scattered pulse pro- files at lower frequency. It reports a simulation to show the scattering and descatter- ing of pulse profiles and PPA curves, and as a practical application the lower frequency profiles and PPA curves of PSR 1356-60, PSR 1831-03, PSR 1838＋04, PSR 1859＋03 and PSR 1946＋35 are obtained. It is found that the original pulse profiles and PPA curves can be recovered.展开更多
Voyagers,the first and the only mission sent by human beings beyond the end of the solar wind,might be out of service in just several years.In the cosmos beyond 2025,very likely no artificial detector will be flying a...Voyagers,the first and the only mission sent by human beings beyond the end of the solar wind,might be out of service in just several years.In the cosmos beyond 2025,very likely no artificial detector will be flying at the outer brim of the solar system.The Interstellar Express,a mission proposed by CAS scientists,might come timely as a possible successor to fill in the gap.Unlike Voyagers,its detectors are expected to fly not only to the nose part of the heliosphere,but also the tail part and the altitude dimension.As planned in the shortterm stage of its three-step layout,the first two detectors will be launched by the end of 2025,if everything goes well.展开更多
Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible throug...Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.展开更多
Interstellar scintillation(ISS)caused by scattering from electron density microstructure(?1 AU)provides unequaled spatial resolving power for a number of applications in astronomy.These include studies of the interste...Interstellar scintillation(ISS)caused by scattering from electron density microstructure(?1 AU)provides unequaled spatial resolving power for a number of applications in astronomy.These include studies of the interstellar medium on scales as small as 100 km and constraints on emission structure in the magnetospheres of compact objects on similar scales.展开更多
According to models such as panspermia or the Nebula-Relay hypothesis,the ancestors of life on Earth once lived in molecular clouds.Then what are the energy source and bioenergetics for such lifeforms?A new bioenerget...According to models such as panspermia or the Nebula-Relay hypothesis,the ancestors of life on Earth once lived in molecular clouds.Then what are the energy source and bioenergetics for such lifeforms?A new bioenergetic mechanism powered by cosmic ray ionization of hydrogen molecules is proposed and its relation with the origin of chemiosmosis is also discussed in this paper.Based on this mechanism,the Last Universal Common Ancestor may be a type of lifeform that utilizes hydrogen molecules as donors of electron transport chains.展开更多
A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and a...A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and are located on the galactic plane XY in a narrow zone inclined by 25°to the galactic axis Y.The following estimates of the parameters of the Radcliffe wave were obtained:(a)the maximum value in periodic perturbations of vertical coordinates Z_(max)=92±10pc with the wavelength of these perturbations λ_(z)=4.82±0.09 kpc;(b)the maximum value of the velocity of vertical disturbances Wmax=4.36±0.12km s^(-1) with disturbance wavelengthλ_(W)=1.78±0.02 kpc.Note that the results of the vertical velocity analysis are first-class in accuracy and completely new.展开更多
With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,s...With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.展开更多
I reminisce on my early life in Section 1;on my education in Sections 2 and 3;on the years at Princeton as a research astronomer in Section 4;on the years on the faculty at Chicago in Section 5;on research on Diffuse ...I reminisce on my early life in Section 1;on my education in Sections 2 and 3;on the years at Princeton as a research astronomer in Section 4;on the years on the faculty at Chicago in Section 5;on research on Diffuse Interstellar Bands(DIBs) in Section 6;on construction of the 3.5 m telescope at Apache Point Observatory(APO)in Section 7;on work on the Sloan Digital Sky Survey(SDSS) in Section 8;on work in public education in Chicago in Section 9;and on my travels in Section 10. My main science research is of an observational nature,concerning Galactic and intergalactic interstellar gas. Highlights for me included my work on the orbiting telescope Copernicus, including the discovery of interstellar deuterium;early observations of absorption associated with fivetimes ionized oxygen;and discoveries concerning the phases of gas in the local interstellar medium, based on previously unobservable interstellar UV spectral lines. With other instruments and collaborations, I extended interstellar UV studies to the intergalactic cool gas using quasi-stellar object QSO absorption lines redshifted to the optical part of the spectrum;provided a better definition of the emission and morphological character of the source of absorption lines in QSO spectra;and pursued the identification of the unidentified DIBs. For several of these topics, extensive collaborations with many scientists were essential over many years. The conclusions developed slowly, as I moved from being a graduate student at Chicago, to a research scientist position at Princeton and then to a faculty position at Chicago. At each stage of life, I was exposed to new technologies adaptable to my science and to subsequent projects. From high school days, I encountered several management opportunities which were formative. I have been extremely fortunate both in scientific mentors I had and in experimental opportunities I encountered.展开更多
Chemical elements in space can be synthesized by stellar nuclear reactors. Studying the dynamics of processes occurring in the stars introduces a concept of the ensemble-averaged stellar reactor. For future interstell...Chemical elements in space can be synthesized by stellar nuclear reactors. Studying the dynamics of processes occurring in the stars introduces a concept of the ensemble-averaged stellar reactor. For future interstellar missions, the terrestrial and solar abundances were compared with considerable number of stars allocated in the ~200 pc solar neighborhood. According to the value of the effective temperature, four stellar classes are distinguished, for which the correlation coefficients and standard deviation are calculated. The statement about the possibility of transferring heavy elements synthesized by stars over long distances in space has been completely refuted. There is no immutability of the distribution of elements on neighboring stars and in the Solar System. It is shown that chemical elements are mainly synthesized inside each stellar reactor. The theory of the buoyancy of elements is generalized to stars. It has been suggested that stars overheat due to a shift in the parameters of nuclear processes occurring inside stars, which leads to the synthesis of heavy elements.展开更多
The possibility of the life origin in the stellar systems, located at a distance of ~200 pc from the solar system, was investigated. The stars, in the spectrums of which C (carbon), O (oxygen), N (nitrogen), and P (ph...The possibility of the life origin in the stellar systems, located at a distance of ~200 pc from the solar system, was investigated. The stars, in the spectrums of which C (carbon), O (oxygen), N (nitrogen), and P (phosphorus) are found, are called DNA-stars. Based on stellar abundances a new method for searching for habitable exoplanets has been developed and a list of 48 DNA-stars in the solar neighborhood, on which life is possible, has been defined. The quota of DNA-stars is equal 1.3% of the total amount of Hypatia Stellar Catalog. Only three DNA-stars out of selected 48 stars belong to the spectral class as our Sun (G2V). The closest to the solar system is the DNA-star with the number HIP 15510, which belongs to the G8V class and is 6 pc away from the solar system. Nine DNA-stars, which have the highest chemical similarity with solar spectrum, were identified. It is identified that one of these nine stars, HIP 24681, has six planets.展开更多
The transition radiation of a charged particle crossing the interface of two media having a monatomic impurity layer is investigated. It is shown that at sliding angles of incidence of a particle on the boundary of th...The transition radiation of a charged particle crossing the interface of two media having a monatomic impurity layer is investigated. It is shown that at sliding angles of incidence of a particle on the boundary of the media, the transition radiation is mainly determined by the properties of the surface layer. The possibility of using transition radiation to study the surface of substances is discussed. In addition, due to the hard radiation present in space, this research may be important for the use of light monoatomic layers as a material for satellite antennas, “solar sails” and cover layers in a future space (interstellar) mission.展开更多
大质量恒星强烈的反馈深刻影响其周围的星际介质,并可能触发下一代恒星形成.S187是位于银河系第2象限的大质量恒星形成区,呈现出“扫集-坍缩”的触发式恒星形成模式.基于“银河画卷”巡天^(12)CO/^(13)CO/C^(18)O(J=1-0,下文J=1-0为简...大质量恒星强烈的反馈深刻影响其周围的星际介质,并可能触发下一代恒星形成.S187是位于银河系第2象限的大质量恒星形成区,呈现出“扫集-坍缩”的触发式恒星形成模式.基于“银河画卷”巡天^(12)CO/^(13)CO/C^(18)O(J=1-0,下文J=1-0为简便起见省略)谱线数据,对S187区域分子云的基本性质开展了研究,探索了该区域大质量恒星对分子云的反馈.利用GaussPy+和聚类算法,在该区域证认了32个分子云,并结合Gaia(Global Astrometric Interferometer for Astrophysics)卫星恒星消光数据测量得到其中8个分子云的距离.S187区域由^(13)CO和C^(18)O示踪的相对致密的气体含量相比于银道面第2象限大部分区域的分子云高出1–2个量级.S187区域分子云中证认了243个^(13)CO团块和98个C^(18)O团块,其中有7个^(13)CO团块和5个C^(18)O团块有形成大质量恒星的潜力.研究结果显示,大质量恒星的反馈对其周围分子云的聚集作用明显,为下一代大质量恒星的形成提供了条件.展开更多
基金the National Natural Science Foundation of China(No.11973075 and No.11433008).
文摘Molecular oxygen(O2)is essential to human beings on the earth.Although elemental oxygen is rather abundant,O2 is rare in the interstellar medium.It was only detected in two galactic and one extra-galactic region.The inconsistency between observations and theoretical studies is a big challenge for astrochemical models.Here we report a two-phase modeling research of molecular oxygen,using the Nautilus gas-grain code.We apply the isothermal cold dense models in the interstellar medium with two typical sets of initial elemental abundances,as well as the warm-up models with various physical conditions.Under cold dense conditions,we nd that the timescales for gas-phase CO,O2 and H2O to reach peak values are dependent on the hydrogen density and are shortened when hydrogen density increases.In warm-up models,O2 abundances are in good agreement with observations at temperatures rising after 10^5 yr.In both isothermal and warm-up models,the steady-state O2 fractional abundance is independent of the hydrogen density,as long as the temperature is high enough(>30 K),at which O2 is prevented from signi cant depleting onto grain surface.In addition,low density is preferable for the formation of O2,whether molecular oxygen is under cold conditions or in warm regions.
基金the support of the National SKA Program of China(No.2022SKA0120101)National Natural Science Foundation of China(Nos.U1931203 and 12233007)
文摘Magnetic fields appear to be ubiquitous in the astrophysical environments of our Universe,but are still poorly understood despite playing an important role in understanding different-scale celestial objects(e.g.,Earth,planets,stars,normal galaxies,active galactic nuclei,clusters etc.).We briefly review the results and progress in magnetic field estimation based on rotation measures from the large-scale interstellar medium,megaparsec-scale radio jets to the plasma near the black-hole horizon.We find that there is no evident correlation between electron density and magnetic field in warm ionized plasma,which suggests that the estimation of the magnetic field from the ratio of the rotation measure and dispersion measure correctly reflects the intrinsic field.The estimation of the magnetic field from the rotation measure is also discussed near the black hole horizon in M 87.The Square Kilometre Array will greatly improve the understanding of the magnetic field in our Universe,which will provide high-quality polarization imaging and extragalactic rotation measures in the near future.
文摘By simple arguments, it is shown how alkaline types of atoms can be seen in dense molecular clouds depending on the average temperature of such regions of the Universe. This paper predicts infrared lines of such atoms that could be seen in molecular clouds. The theory is developed in the first part and the predicted experimental results will follow. It results that the alkaline atoms modelized using the short-range polarization potential are found in quantum states <em>n</em><sub>*</sub> > 2.
基金funded by the National Natural Science Foundation of China(Grant No.10973026)the key program project of the Joint Fund of Astronomy by NSFC and CAS(No.11178001)
文摘Interstellar scattering causes broadening and distortion in the mean pulse profiles and polarization position angle （PPA） curves of pulsars, especially pulse profiles observed at lower frequencies. This paper implements a method to recover the pulse profiles and PPA curves of five pulsars which have obvious scattered pulse pro- files at lower frequency. It reports a simulation to show the scattering and descatter- ing of pulse profiles and PPA curves, and as a practical application the lower frequency profiles and PPA curves of PSR 1356-60, PSR 1831-03, PSR 1838＋04, PSR 1859＋03 and PSR 1946＋35 are obtained. It is found that the original pulse profiles and PPA curves can be recovered.
文摘Voyagers,the first and the only mission sent by human beings beyond the end of the solar wind,might be out of service in just several years.In the cosmos beyond 2025,very likely no artificial detector will be flying at the outer brim of the solar system.The Interstellar Express,a mission proposed by CAS scientists,might come timely as a possible successor to fill in the gap.Unlike Voyagers,its detectors are expected to fly not only to the nose part of the heliosphere,but also the tail part and the altitude dimension.As planned in the shortterm stage of its three-step layout,the first two detectors will be launched by the end of 2025,if everything goes well.
基金supported by the National Natural Science Foundation of China(Grant No.12003047)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(Grant No.2022A03013-2)+2 种基金the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2022D01D85)support by the Deutsche Forschungsgemeinschaft(DFG)through the Heisenberg programme(Project No.433075039)financial support from“Programme National de Cosmologie et Galaxies”(PNCG)of CNRS/INSU,France。
文摘Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.
文摘Interstellar scintillation(ISS)caused by scattering from electron density microstructure(?1 AU)provides unequaled spatial resolving power for a number of applications in astronomy.These include studies of the interstellar medium on scales as small as 100 km and constraints on emission structure in the magnetospheres of compact objects on similar scales.
基金Supported by the National Key Research and Development Program of China(Grant No.2016YFA0400200)the National Natural Science Foundation of China(Grants No.11773075)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2016288).
文摘According to models such as panspermia or the Nebula-Relay hypothesis,the ancestors of life on Earth once lived in molecular clouds.Then what are the energy source and bioenergetics for such lifeforms?A new bioenergetic mechanism powered by cosmic ray ionization of hydrogen molecules is proposed and its relation with the origin of chemiosmosis is also discussed in this paper.Based on this mechanism,the Last Universal Common Ancestor may be a type of lifeform that utilizes hydrogen molecules as donors of electron transport chains.
文摘A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and are located on the galactic plane XY in a narrow zone inclined by 25°to the galactic axis Y.The following estimates of the parameters of the Radcliffe wave were obtained:(a)the maximum value in periodic perturbations of vertical coordinates Z_(max)=92±10pc with the wavelength of these perturbations λ_(z)=4.82±0.09 kpc;(b)the maximum value of the velocity of vertical disturbances Wmax=4.36±0.12km s^(-1) with disturbance wavelengthλ_(W)=1.78±0.02 kpc.Note that the results of the vertical velocity analysis are first-class in accuracy and completely new.
基金support of the China National Key Program for Science and Technology Research and Development of China(2022YFA1602901)the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and 11873051)+3 种基金the CAS Project for Young Scientists in Basic Research grant(No.YSBR-062)the K.C.Wong Education Foundationthe science research grants from the China Manned Space Projectsupport from the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.
文摘I reminisce on my early life in Section 1;on my education in Sections 2 and 3;on the years at Princeton as a research astronomer in Section 4;on the years on the faculty at Chicago in Section 5;on research on Diffuse Interstellar Bands(DIBs) in Section 6;on construction of the 3.5 m telescope at Apache Point Observatory(APO)in Section 7;on work on the Sloan Digital Sky Survey(SDSS) in Section 8;on work in public education in Chicago in Section 9;and on my travels in Section 10. My main science research is of an observational nature,concerning Galactic and intergalactic interstellar gas. Highlights for me included my work on the orbiting telescope Copernicus, including the discovery of interstellar deuterium;early observations of absorption associated with fivetimes ionized oxygen;and discoveries concerning the phases of gas in the local interstellar medium, based on previously unobservable interstellar UV spectral lines. With other instruments and collaborations, I extended interstellar UV studies to the intergalactic cool gas using quasi-stellar object QSO absorption lines redshifted to the optical part of the spectrum;provided a better definition of the emission and morphological character of the source of absorption lines in QSO spectra;and pursued the identification of the unidentified DIBs. For several of these topics, extensive collaborations with many scientists were essential over many years. The conclusions developed slowly, as I moved from being a graduate student at Chicago, to a research scientist position at Princeton and then to a faculty position at Chicago. At each stage of life, I was exposed to new technologies adaptable to my science and to subsequent projects. From high school days, I encountered several management opportunities which were formative. I have been extremely fortunate both in scientific mentors I had and in experimental opportunities I encountered.
文摘Chemical elements in space can be synthesized by stellar nuclear reactors. Studying the dynamics of processes occurring in the stars introduces a concept of the ensemble-averaged stellar reactor. For future interstellar missions, the terrestrial and solar abundances were compared with considerable number of stars allocated in the ~200 pc solar neighborhood. According to the value of the effective temperature, four stellar classes are distinguished, for which the correlation coefficients and standard deviation are calculated. The statement about the possibility of transferring heavy elements synthesized by stars over long distances in space has been completely refuted. There is no immutability of the distribution of elements on neighboring stars and in the Solar System. It is shown that chemical elements are mainly synthesized inside each stellar reactor. The theory of the buoyancy of elements is generalized to stars. It has been suggested that stars overheat due to a shift in the parameters of nuclear processes occurring inside stars, which leads to the synthesis of heavy elements.
文摘The possibility of the life origin in the stellar systems, located at a distance of ~200 pc from the solar system, was investigated. The stars, in the spectrums of which C (carbon), O (oxygen), N (nitrogen), and P (phosphorus) are found, are called DNA-stars. Based on stellar abundances a new method for searching for habitable exoplanets has been developed and a list of 48 DNA-stars in the solar neighborhood, on which life is possible, has been defined. The quota of DNA-stars is equal 1.3% of the total amount of Hypatia Stellar Catalog. Only three DNA-stars out of selected 48 stars belong to the spectral class as our Sun (G2V). The closest to the solar system is the DNA-star with the number HIP 15510, which belongs to the G8V class and is 6 pc away from the solar system. Nine DNA-stars, which have the highest chemical similarity with solar spectrum, were identified. It is identified that one of these nine stars, HIP 24681, has six planets.
文摘The transition radiation of a charged particle crossing the interface of two media having a monatomic impurity layer is investigated. It is shown that at sliding angles of incidence of a particle on the boundary of the media, the transition radiation is mainly determined by the properties of the surface layer. The possibility of using transition radiation to study the surface of substances is discussed. In addition, due to the hard radiation present in space, this research may be important for the use of light monoatomic layers as a material for satellite antennas, “solar sails” and cover layers in a future space (interstellar) mission.
文摘大质量恒星强烈的反馈深刻影响其周围的星际介质,并可能触发下一代恒星形成.S187是位于银河系第2象限的大质量恒星形成区,呈现出“扫集-坍缩”的触发式恒星形成模式.基于“银河画卷”巡天^(12)CO/^(13)CO/C^(18)O(J=1-0,下文J=1-0为简便起见省略)谱线数据,对S187区域分子云的基本性质开展了研究,探索了该区域大质量恒星对分子云的反馈.利用GaussPy+和聚类算法,在该区域证认了32个分子云,并结合Gaia(Global Astrometric Interferometer for Astrophysics)卫星恒星消光数据测量得到其中8个分子云的距离.S187区域由^(13)CO和C^(18)O示踪的相对致密的气体含量相比于银道面第2象限大部分区域的分子云高出1–2个量级.S187区域分子云中证认了243个^(13)CO团块和98个C^(18)O团块,其中有7个^(13)CO团块和5个C^(18)O团块有形成大质量恒星的潜力.研究结果显示,大质量恒星的反馈对其周围分子云的聚集作用明显,为下一代大质量恒星的形成提供了条件.
