Astronomical Review最新文献

{"title":"A guided map to the spiral arms in the galactic disk of the Milky Way","authors":"J. Vallée","doi":"10.1080/21672857.2017.1379459","DOIUrl":"https://doi.org/10.1080/21672857.2017.1379459","url":null,"abstract":"Abstract An up-to-date overview of the recent history is given, aiming is to present a helpful working guide to the literature and at the same time introduce key systems and observational results, starting from the Sun and going toward the Galactic Center and parts of the Zona Galactica Incognita, and beyond. We start by presenting an observational view of the Milky Way’s disk plane (cartographic, dynamical, chemical cross-cut, magnetic). This included the four long spiral arms in the disk of the Milky Way galaxy, their geometry, components, velocity, their widths and internal layers as well as onion-like ordered offsets, the central galactic bars, arm tangents, arm pitch and arm shape, arm origins near the Galactic Center, and other possible players in the spiral arm, such as the magnetic field and the dark matter content. After, we present a basic analysis of some theoretical predictions from galactic arm formation: numerical simulations or analytical theories, and observations are checked against predictions from various numerical simulations and analytical (theoretical) models.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127590285","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":"Exozodiacal clouds: hot and warm dust around main sequence stars","authors":"Q. Kral, A. Krivov, D. Defrére, R. van Lieshout, A. Bonsor, J. Augereau, P. Thebault, S. Ertel, J. Lebreton, O. Absil","doi":"10.1080/21672857.2017.1353202","DOIUrl":"https://doi.org/10.1080/21672857.2017.1353202","url":null,"abstract":"Abstract A warm/hot dust component (at temperature 300 K) has been detected around 20% of A, F, G, K stars. This component is called ‘exozodiacal dust’ as it presents similarities with the zodiacal dust detected in our solar system, even though its physical properties and spatial distribution can be significantly different. Understanding the origin and evolution of this dust is of crucial importance, not only because its presence could hamper future detections of Earth-like planets in their habitable zones, but also because it can provide invaluable information about the inner regions of planetary systems. In this review, we present a detailed overview of the observational techniques used in the detection and characterisation of exozodiacal dust clouds (‘exozodis’) and the results they have yielded so far, in particular regarding the incidence rate of exozodis as a function of crucial parameters such as stellar type and age, or the presence of an outer cold debris disc. We also present the important constraints that have been obtained, on dust size distribution and spatial location, using state-of-the-art radiation transfer models on some of these systems. Finally, we investigate the crucial issue of how to explain the presence of exozodiacal dust around so many stars (regardless of their ages) despite the fact that such dust so close to its host star should disappear rapidly due to the coupled effect of collisions and stellar radiation forces. Several potential mechanisms have been proposed to solve this paradox and are reviewed in detail in this paper. The review finishes by presenting the future of this growing field.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"219 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114745190","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":"The time domain for brown dwarfs and directly imaged giant exoplanets: the power of variability monitoring","authors":"B. Biller","doi":"10.1080/21672857.2017.1303105","DOIUrl":"https://doi.org/10.1080/21672857.2017.1303105","url":null,"abstract":"Abstract Variability has now been robustly observed in a range of L and T type field brown dwarfs, primarily at near-IR and mid-IR wavelengths. The probable cause of this variability is surface inhomogeneities in the clouds of these objects (although other mechanisms may also contribute), causing a semi-periodic variability signal when combined with the rotational modulation from 3 to 20 h period expected for these objects. Variability at similar or even higher amplitudes has recently been observed in young brown dwarfs and planetary mass objects, which share similar as field brown dwarfs, but have considerably lower surface gravities. Variability studies of these objects relative to old field objects is then a direct probe of the effects of surface gravity on atmospheric structure.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"136 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122776438","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":"Robotic telescopes in education","authors":"E. Gomez, M. Fitzgerald","doi":"10.1080/21672857.2017.1303264","DOIUrl":"https://doi.org/10.1080/21672857.2017.1303264","url":null,"abstract":"The power of robotic telescopes to transform science education has been voiced by multiple sources, since the 1980s. Since then, much technical progress has been made in robotic telescope provision to end users via a variety of different approaches. The educational transformation hoped for by the provision of this technology has, so far, yet to be achieved on a scale matching the technical advancements. In this paper, the history, definition, role and rationale of optical robotic telescopes with a focus on their use in education is provided. The current telescope access providers and educational projects and their broad uses in traditional schooling, undergraduate and outreach are then outlined. From this background, the current challenges to the field, which are numerous, are then presented. This review is concluded with a series of recommendations for current and future projects that are apparent and have emerged from the literature.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124698213","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":"Formation of exomoons: a solar system perspective","authors":"A. Barr","doi":"10.1080/21672857.2017.1279469","DOIUrl":"https://doi.org/10.1080/21672857.2017.1279469","url":null,"abstract":"Satellite formation is a natural by-product of planet formation. With the discovery of numerous extrasolar planets, it is likely that moons of extrasolar planets (exomoons) will soon be discovered. Some of the most promising techniques can yield both the mass and radius of the moon. Here, I review recent ideas about the formation of moons in our Solar System, and discuss the prospects of extrapolating these theories to predict the sizes of moons that may be discovered around extrasolar planets. It seems likely that planet-planet collisions could create satellites around rocky or icy planets which are large enough to be detected by currently available techniques. Detectable exomoons around gas giants may be able to form by co-accretion or capture, but determining the upper limit on likely moon masses at gas giant planets requires more detailed, modern simulations of these processes.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"198 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121012161","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":"Time-domain studies of M31","authors":"C.-H. Lee","doi":"10.1080/21672857.2016.1270028","DOIUrl":"https://doi.org/10.1080/21672857.2016.1270028","url":null,"abstract":"Abstract M31, our closest neighboring galaxy, is a stepping stone to studies of stellar evolution, star formation, galaxy evolution, and cosmology. However, due to the difficulties of performing photometry in such crowded fields and the lack of wide cameras to encompass the entire galaxy, there has not been a complete census of the stellar contents of M31. The advent of wide-field camera provides us a unique opportunity to have a complete view of our neighboring galaxy, enabling an inventory of its variable content. We present a review of recent progresses of wide-field, high cadence surveys of M31, covering different population of variables and transients. We also outline future studies enabled by ongoing and upcoming facilities.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124115062","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":"Modeling the radiation field in the Greenhouse effect – history and evolution","authors":"S. Bressler, G. Shaviv","doi":"10.1080/21672857.2015.1085161","DOIUrl":"https://doi.org/10.1080/21672857.2015.1085161","url":null,"abstract":"This article reviews the scientific physical and mathematical evolution of models to calculate the Greenhouse effect (GHE) and radiative transfer in planetary atmospheres. It examines the set of assumptions made in the models and concludes with a short discussion about the next steps in GHE modeling.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129726153","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":"Biological entities and DNA-containing masses isolated from the stratosphere-evidence for a non-terrestrial origin","authors":"M. Wainwright","doi":"10.1080/21672857.2015.1087751","DOIUrl":"https://doi.org/10.1080/21672857.2015.1087751","url":null,"abstract":"Here, we provide images of a variety of biological entities (BEs) which we have sampled from the stratosphere at heights of between 23 and 27 km. The BEs have unusual morphology and are generally not representatives of known terrestrial organisms. Analysis using SEM and EDX shows that all of the BEs contain only C and O and are not associated on the sampling stubs with pollen, grass or other terrestrial organisms. Images are provided of some of the BEs which were sampled from our first and third successful sampling trips, the second trip isolated inorganic micrometeorites, but not BEs. We conclude that the evidence points to a space origin for these stratosphere-derived BEs. Clumps of stratospheric material with individual diameters of 10–30 μm were also isolated in a sterile manner from a height of 41 km. The masses showed no obvious morphology, but stained positive for DNA and are therefore considered to be biological. We suggest that, like the BEs, the masses are arriving to the stratosphere from space and not upcoming from Earth; evidence is provided to support this view.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132052472","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":"A Peculiar Cosmology from Supernovae Type 1a with Derivations of G and Modified Newtonian Dynamics Acceleration","authors":"Berry Cottrell Ives","doi":"10.1080/21672857.2015.11519741","DOIUrl":"https://doi.org/10.1080/21672857.2015.11519741","url":null,"abstract":"Abstract A revised Hubble-type relationship is derived from redshift data of supernova type 1a. Estimated H0 is 68.24 km/sec per Mpc, very close to the value 67.80 (0.77) km/sec per Mpc published in the Planck satellite CMB studies. A universe in a state of accelerated contraction is inferred. The maximum expanded state is estimated to have had a “virtual gravitational radius” of 185.6 Gly which occurred 171.8 Gyr ago, and the current radius is estimated at 26.53 Gly. This radius applies to all observers. A big bounce scenario appears consistent with the parabolic path of the past expansion and current contraction eras, with a full cycling period of about 371 Gyr. The end of the current contraction era is estimated to occur about 13.8 Gyr in the future. The value of the Newtonian gravitational constant G is derived based on an acceleration parameter that is estimated along with Ho. The universal acceleration rate, in the range of 1.03e-10 to 1.16e-10 m/s2, is consistent with modified Newtonian dynamics acceleration of astronomical objects, estimated at 1.2(±0.2) e-10 m/s2. G is found to vary over time with the square of the gravitational radius. The derived value for G in the present is 5.860 m3kg-1s-2, which is about 12% less than the consensus value of 6.674 m3kg-1s-2. This relative error is small in the context of this analysis.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"125 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114413549","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":"The occurrence of non-pulsating stars in the γ Dor and δ Sct pulsation instability regions: results from Kepler quarter 14–17 data","authors":"J. Guzik, P. Bradley, J. Jackiewicz, J. Molenda–Żakowicz, K. Uytterhoeven, K. Kinemuchi","doi":"10.1080/21672857.2015.1023120","DOIUrl":"https://doi.org/10.1080/21672857.2015.1023120","url":null,"abstract":"The high precision long time-series photometry of the NASA Kepler spacecraft provides an excellent means to discover and characterize variability in main-sequence stars, and to make progress in interpreting the pulsations to derive stellar interior structure and test stellar models. For stars of spectral types A–F, the Kepler data revealed a number of surprises, such as more hybrid pulsating Sct and Dor pulsators than expected, pulsators lying outside of the instability regions predicted by theory, and stars that were expected to pulsate, but showed no variability. In our 2013 Astronomical Review article, we discussed the statistics of variability for 633 faint (Kepler magnitude 14–16) spectral type A–F stars observed by Kepler during Quarters 6–13 (June 2010–June 2012). We found six stars that showed no variability with amplitude 20 ppm or greater in the range 0.2–24.4 cycles/day, but whose positions in the log diagram place them in the Sct or Dor pulsation instability regions established from pre-Kepler ground-based observations. Here, we present results for an additional 2137 stars observed during Quarters 14–17 (June 2012–May 2013). This sample is not unbiased, as we limited our target list to stars showing variability in Quarter 0 full-frame images to enhance our variable star discovery rate. We find that 990 stars, or 46%, show no frequencies in the Fourier transform of their light curves down to the 20-ppm level, a smaller percentage than the 60% of our Q6–13 sample. We find 34 additional stars that lie within the ground-based Dor/ Sct pulsation instability regions; their lack of pulsations requires explanation. In the analysis for our first paper, we included a K offset to the Kepler Input Catalog to take into account an average systematic difference between the KIC values and the derived from SDSS color photometry for main-sequence F stars. We compare the KIC value and the derived from spectroscopy taken by the LAMOST instrument for 54 stars common to both samples. We find no trend to support applying this offset; the trend instead shows that a small average temperature decrease relative to the KIC may be more appropriate for the stars in our spectral-type range. If the 229 K offset is omitted, only 17 of our 34 “constant” stars fall within the pulsation instability regions. The comparisons with LAMOST-derived log also show that the KIC log may be too large for stars with KIC log values . For the two “constant” stars in the instability region that were also observed by LAMOST, the LAMOST values are cooler than the KIC by several hundred K, and would move these stars out of the instability regions. It is possible that a more accurate determination of their and log would move some of the other “constant” stars outside of the instability regions. However, if average (random) errors in ( K) and an offset in log from the KIC values are taken into account, 15–52 stars still persist within the instability regions. Explanations for these “consta","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116946774","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}