American Journal of Astronomy and Astrophysics最新文献

{"title":"An Analytical Model for Cosmology with a Single Input, the Redshift","authors":"N. Mostaghel","doi":"10.11648/j.ajaa.20241102.12","DOIUrl":"https://doi.org/10.11648/j.ajaa.20241102.12","url":null,"abstract":"We propose an analytical model for cosmology which requires only one parameter as an input. This parameter is the redshift. The model is based on conservation of energy, Planck’s Radiation Law, and the relation between energy and frequency of waves. The model yields the current age of the universe, the age of the universe at the CMB emission, as well as the time histories of its expansion velocity and acceleration. The model also is used to show the existence of a constant energy per unit area, associated with the momentum energy of photons, which generates the pressure that perpetuates the expansion of the universe. The model is completely independent of the ɅCDM model but implicitly includes the effects of gravity. Using the model we show the existence of a constant in nature that under certain assumptions can represent the Hubble constant. We have used the model to derive the Hubble constants measured by Reiss et al. and by the Planck Collaboration. Using the model we show that the path of light in the Planck collaboration measurement is along a circular arc, while the Reiss et al. measurement path is exactly along the chord of the same circular arc. The difference in the light travel times along these two paths matches exactly the difference between the two measured values for the Hubble constant, as measured by Reiss et al. and as measured by the Planck Collaboration. This result explains the cause of tension between the two methods of measurement.\u0000","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"5 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141836686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantification of Near-Earth Objects Between 1990-2021: An Overview","authors":"Osuji Emmanuel Uchenna, Ugwu Monday, Aernan Andofa, Ojima Ocheni, Aneke Ukpabi, Wash Albert, Madike Emeka Michael, Justus Chukwunonyerem, O. Obinna, Okoro Emmanuel Chineche, Okpara Richard Tobechi, Vincent Osinachi Ezinwa, Ekechukwu Uzoamaka, Obasi Rita Chioma, Ezenwukwa Nnenna Dorathy","doi":"10.11648/j.ajaa.20231001.12","DOIUrl":"https://doi.org/10.11648/j.ajaa.20231001.12","url":null,"abstract":"","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114562688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Double Spiral Cote's Galaxies NGC 1566 and the Southern Pinwheel, and Cyclone in the South Sandwich Islands","authors":"R. Gobato, Abhijit Mitra, Poulomi Mullick","doi":"10.11648/j.ajaa.20231001.11","DOIUrl":"https://doi.org/10.11648/j.ajaa.20231001.11","url":null,"abstract":"","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139370352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"About the Free and Forced Nutation: The Daily Nutation","authors":"M. Ciobanu","doi":"10.11648/j.ajaa.20210902.12","DOIUrl":"https://doi.org/10.11648/j.ajaa.20210902.12","url":null,"abstract":"To explain the nutation phenomenon, Euler chose a geocentric frame of coordinates to present his dynamical equations. In accordance with his formulas, the nutation is caused by a momentum relative to the Earth's center, due to certain external forces. Further, Poinsot presented a special case of the Euler's equations, when any momentum of those certain external forces does not exist. Due to a problematic approximation, Poinsot announced that in this case may take place a nutation period of 10 month, named “free period”, to distinguish it from the Euler's dynamical solution, known as “forced nutation”. After Poinsot, the notion of “free nutation” was extended also to those nutation phenomena which have only a geophysical origin, without a momentum of certain external forces. Usually, the daily nutation is considered as being a free nutation phenomenon. In order to search for a forced daily nutation component, the daily trajectory of the Earth-Moon barycenter inside the Earth is used (a simple scheme of this barycenter trajectory is presented in a geocentric system of axes). Finally, if the ecliptic line is accepted to be described by the Earth-Moon barycenter, it must be accepted, too, that a torque due the Sun and the Moon acts during a sideral day interval on diurnal Earth rotation around its axis. Due to the small value of the nutation constant, a period of 18,6 years is needed to correctly and completely detect the forced daily nutation; this phenomenon permanently presents very fine variations depending on the longitude of the ascending lunar node, the Moon’s declination and the Sun’s ecliptic longitude.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126428361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intergalactic Media Densities of Extragalactic Radio Sources and Source Ages","authors":"E. Chukwuemerie","doi":"10.11648/J.AJAA.20210902.11","DOIUrl":"https://doi.org/10.11648/J.AJAA.20210902.11","url":null,"abstract":"In this paper, we use analytical methods with some plausible assumptions to develop a mathematical model which may be used to obtain estimate of density of the intergalactic medium (IGM). This relation suggests that the plot of the linear sizes against the bolometric luminosities of the extragalactic radio sources in our sample should be able to furnish us with an estimate of the density of IGM in which the radio sources are domiciled. Moreover, for the purpose of obtaining an empirical relation similar to the theoretical model, we carry out linear regression analysis of linear sizes and luminosities of the 31 radio galaxies in our sample. The regression result shows an empirical relationship between observed source linear sizes and observed bolometric luminosities with slight correlation whose coefficient is 4. Moreover, we compared the theoretical relation and the empirical relation to obtain an estimate of the particle number density of the IGM in which the radio sources are located. The estimate indicates a very low density when compared with the values obtained by authors for the compact steep spectrum (CSS) sources. However, while the linear sizes of the CSS sources are of sub-galactic dimensions – they are located within the interstellar media (ISM) – those of the large extended extragalactic radio sources extend into the intergalactic media. The staggering difference in these obtained densities of IGM and ISM simply supports the general notion that there is a sharp decrease in the density at the IGM–ISM interface. Moreover, using theoretical approach again, with some plausible assumptions, we find another relation which may be used to estimate the ages of extragalactic radio sources. This relation possibly indicates that the plot of the linear sizes against velocities of the radio jets of the radio sources in our sample should be able to supply us with an estimate of the sources’ ages. We find from the simple linear regression analysis of linear sizes and jet velocities of the radio galaxies in our sample, a relation with correlation coefficient given as 4, which is also marginal. Comparison of the two relations – theoretical and the empirical relations – gives an estimate of age of the radio sources. The value shows that these large extended extragalactic radio sources are old sources.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"177 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129574347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On Cosmic Epochand Linear Size/Luminosity Evolution of Compact Steep Spectrum Sources","authors":"E. Chukwuemerie","doi":"10.11648/J.AJAA.20210901.12","DOIUrl":"https://doi.org/10.11648/J.AJAA.20210901.12","url":null,"abstract":"We have used analytical methods in this paper to obtain a mathematical relation that describes relationship between the linear size of compact steep spectrum (CSS) sources and their redshift. Result shows that the source linear size has an inverse power-law dependence on the redshift. Moreover, for the purpose of obtaining an empirical relation that shows relationship between the liner size and the redshift, we carry out simple linear regression analyses on the observed linear sizes of the CSS sources in our sample against their respective observed redshifts. Results of the analyses indicate that the linear sizes of the quasars have direct power law relationship with their respective redshifts; while the converse is the case for their galaxy counterparts. Their correlation coefficients are marginal. In comparison with the obtained theoretical relation, we notice that for the CSS quasars, the linear size–redshift data show an inverse correlation. This is comparable with the theoretical relation. So, it suggests that the dynamical evolution of the source linear sizes may have some cosmological effects on it. However, the converse is the case for the CSS galaxies – the correlation is direct. The possible explanation for this difference is that quasars are observed at higher redshifts than their galaxy counterparts. Hence, the cosmological effects are expected to be more pronounced on the quasars. Furthermore, we use analytical methods again to obtain a theoretical relation that shows relationship between luminosity and redshift. The relation indicates that luminosity of a radio source has an inverse power-law relationship with redshift. This suggestively implies that the intrinsic luminosity of a radio source may be modified by cosmological evolution. Moreover, for the purpose of obtaining an empirical relation for comparison with the theory, we carry out linear regression analysis of observed luminosities against observed redshifts of the CSS quasars and galaxies in our sample. Results show that luminosities have excellent direct power-law relationship with redshifts. However, this is in contradiction to the obtained theory which shows inverse relationship between the two parameters. This excellent direct correlation has been attributable by some authors to strong luminosity selection effects in which samples with high luminosities are found at high redshifts. Therefore, if the selection effects are taken care of, we may be able to see the comparability of the theory with the empirical relation. Hence, we conclude that source radiated power may have some cosmological implications just like we saw in the size/redshift relation.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126948696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Alternative Model of Rotation Curve that Explains Anomalous Orbital Velocity, Mass Discrepancy and Structure of Some Galaxies","authors":"P. Rivera, Marco Rivera","doi":"10.31219/osf.io/97ufw","DOIUrl":"https://doi.org/10.31219/osf.io/97ufw","url":null,"abstract":"A new model of galaxy rotation based on the cyclostrophic model of vortices found in nature is developed. The model is tested using the SPARC dataset of 175 galaxies and a smaller dataset comprising of 60 galaxies. Analysis of the datasets showed that galactic rotation can be adequately described using the observed surface brightness of galaxies and the newly developed cyclostrophic velocity model. The use of the luminosity and the inverse mass-to-light ratio in lieu of the surface brightness, also yield a very good fit of the observed and computed galaxy rotation velocity. Evidently, galactic rotation greatly depends on the cyclostrophic balance of the pressure gradient and the centrifugal forces and the seismic-induced radial expansion occurring in various stars. This is the most probable origin of the action of a single force law that has been overlooked in previous studies. Therefore, the need for a super-massive black hole at the center of galaxies or hidden dark matter can be eliminated. Attractive gravitational force can occur even without a massive black hole at the center of galaxies. There appears to be a pressure gradient force between the center and the outer parts of galaxies that sustains attraction. The cyclostrophic model appears to be the physical basis of the Tully-Fisher relation. Furthermore, the missing mass problem associated with galactic rotation can be attributed to the orbital expansion of celestial objects perturbed by seismic-induced forces. In addition, massive tremors or starquakes may create a domino effect in perturbing nearby stars along the axis of the seismic-induced force and this could result in the formation of elliptical galaxies as the orbits of seismic-perturbed neighboring stars become larger.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124600668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variability of VTEC Gradient and TEC Rate Index Over Kisumu, Kenya During Selected Quiet and Storm Days of 2013 and 2014","authors":"U. Edward, Ndinya Boniface, O. George","doi":"10.11648/J.AJAA.20190704.13","DOIUrl":"https://doi.org/10.11648/J.AJAA.20190704.13","url":null,"abstract":"Vertical Total electron content (VTEC) gradient or rate of change of TEC (ROT) and total electron content (TEC) rate index or rate of change of TEC index (ROTI) can directly be estimated from receiver independent exchange (RINEX) data and can be used to estimate presence and intensity of ionospheric irregularities. In this paper we present results of the variation of ROT and ROTI over Kisumu, Kenya (Geomagnetic coordinates: 9.64°S, 108.59°E; Geographic coordinates: 0.02°S, 34.6°E) for both selected quiet and disturbed conditions between 1st January 2013 and 31st December 2014 using data derived from NovAtel GSV4004B SCINDA-GPS receiver at Kisumu as a step in establishing ionospheric irregularities over Kisumu, Kenya during a high solar activity period of solar cycle 24. ROT was calculated from filtered average daily VTEC data within intervals of 120 seconds while ROTI was computed over 4 minutes window from ROT. ROT and corresponding ROTI for the selected quiet and storm days were plotted against universal time (UT). The presence and intensity of irregularities on the selected quiet and storm days of the years 2013 and 2014 were determined by checking ROT fluctuations and the corresponding ROTI values from the plots. The obtained results showed increased fluctuation of ROT corresponding with large ROTI values after sunset. The selected storm days of the years 2013 and 2014 had higher ROTI values than the selected quiet days of the years 2013 and 2014. The higher ROTI values during the selected storm days may be attributed to the impact of geomagnetic storms brought about by several competing dynamics including Prompt penetration electric field (PPEF), disturbance dynamo electric field (DDEF) and reduction in electron density due to increased recombination rates. The high ROTI values after sunset were a manifestation of post-sunset plasma irregularities. The obtained results also showed a diurnal trend for ROT and ROTI where ROT increased steadily from 0.00UT to around 12:00UT before falling and having an increased fluctuation between 18:00UT and 20:00UT. This corresponded well with low ROTI values between 0:00UT and 16:00UT followed by high ROTI values between 18:00UT and 20:00UT. The diurnal variability of ROT might have resulted from variation of TEC and which was attributed to changes in the intensity of incoming solar radiation.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130121357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advanced Panspermia of Origin of Life and Evolution","authors":"V. Yeragudipati","doi":"10.11648/J.AJAA.20190704.12","DOIUrl":"https://doi.org/10.11648/J.AJAA.20190704.12","url":null,"abstract":"In this study, a theory on Advanced Panspermia of Origin of Life and Evolution is proposed by establishing (i) striking planetary similarities observed for parents and their children of their respective birth times similar to matching bands in DNA Fingerprinting images of them establishing heredity; (ii) the number of DNA entries required to differentiate one person from the other being identical to the number of planetary configurations that would result (iii) the Lunar Magnetism Orchestrated Menstrual Cycle in Symphony of Reproduction of Life, and (iv) Cambrian Explosion witnessed origin of complex vertebrates simultaneously and all of a sudden. All the above comprise the strongest scientific evidence in the “Breakthrough of “Advanced Panspermia of Origin of Life and Evolution”. Perhaps, the totipotent cell, formed in space under abiotic conditions during the early days of the solar system, picks up different magnetic signals from out of the solar symphony and at different stages of its development and the DNA is thus programmed. These pre-programmed magnetic memories may be evoked later in evolution when similar magnetic signals are repeated. Life came into being from space brought by star dust on the Earth with each major change of climate for evolution at intervals of simple multiples of Geological Time Scale ‘Periods’. The study also discusses of how the Sun, Moon, and planets telegraph their effects to us, via interplanetary space striking Earth's magnetosphere, which are perceived by the neural network of the living beings, which are genetically predisposed to hear specific planetary signals.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123683478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust Performance Analysis on Dynamic Control of Unmanned Aerial Vehicle System Using Bode Plot","authors":"Hteik Tin Cho Nyunt, Thanda Win, H. Tun","doi":"10.11648/J.AJAA.20190704.11","DOIUrl":"https://doi.org/10.11648/J.AJAA.20190704.11","url":null,"abstract":"The paper focuses on the robust performance analysis on dynamic control of unmanned aerial vehicle system with numerical computation. The objectives of this work are to find the appropriate solution for robust stability problems for dynamic control of unmanned aerial vehicle (UAV) system which is critical challenge in the space technology. The background of the theoretical work on digital control system is very important to study the problem of dynamic control system at present. The idea behind the control system stability analysis on digital technology is very important candidate in space technology. The specific purpose on analyzing the performance of dynamic of digital control system for space technology is solved in this paper. The mathematical model of target system is mentioned and analyzed based on the classical control method with digital technology. The related work for modeling of the control system is mentioned and expressed the detailed background for the analysis. The simulation results confirm that the proposed system met the robust performance for digital control of UAV system for reality. The analysis has been carried out based on feedback control system stability for dynamic system as well. The simulation results for stability analysis have been carried out by using MATLAB programming languages.","PeriodicalId":166360,"journal":{"name":"American Journal of Astronomy and Astrophysics","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131128860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}