Astronomical Review最新文献

{"title":"The Physics of Blazar Jets","authors":"M. Urry","doi":"10.1080/21672857.2012.11519698","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519698","url":null,"abstract":"Abstract Because blazars are characterized by beamed emission from relativistic jets aligned with our line of sight, they are ideal sources for studying jet physics. Over the past few years, multiwavelength monitoring of dozens of blazars with the Fermi gamma-ray telescope and optical-infrared telescopes has revealed a close correlation between the synchrotron and high-energy components of blazar spectral energy distributions. This strongly supports a model for the emission mechanism in which gamma-rays are produced when synchrotron-emitting electrons Compton up-scatter ambient synchrotron or thermal photons. Flat-spectrum radio quasars also have a blue, less variable component that is likely to be thermal emission from a slowly varying accretion disk, while BL Lacs have only weak or radiatively inefficient disks. The temporal symmetry of gamma-ray and optical-infrared flares implies that the variability time scales are dominated by light crossing times or the passage of a disturbance through the emission region rather than by the acceleration or energy-loss timescales of the radiating electrons. This new understanding of jet physics for a sizeable blazar sample allows us to refine estimates of jet power, which is important for understanding jet formation and for feedback onto galaxies and the intergalactic medium.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125409444","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":"Water on The Moon, III. Volatiles & Activity","authors":"A. Crotts","doi":"10.1080/21672857.2012.11519702","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519702","url":null,"abstract":"For centuries some scientists have argued that there is activity on the Moon (or water, as recounted in Parts I & II), while others have thought the Moon is simply a dead, inactive world. The question comes in several forms: is there a detectable atmosphere? Does the surface of the Moon change? What causes interior seismic activity? From a more modern viewpoint, we now know that as much carbon monoxide as water was excavated during the LCROSS impact, as detailed in Part I, and a comparable amount of other volatiles were found. At one time the Moon outgassed prodigious amounts of water and hydrogen in volcanic fire fountains, but released similar amounts of volatile sulfur (or SO2), and presumably large amounts of carbon dioxide or monoxide, if theory is to be believed. So water on the Moon is associated with other gases. We review what is known (and touch on what is unknown) about outgassing of various gases from the Moon.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"126 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122461842","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 Heliosheath: The Ultimate Solar System Frontier","authors":"M. Opher","doi":"10.1080/21672857.2012.11519697","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519697","url":null,"abstract":"Abstract The recent measurements in-situby the Voyager spacecrafts, combined with the all-sky images of the heliospheric boundaries by the Interstellar Boundary Explorer (IBEX) mission have transformed radically our knowledge of the boundaries of the heliosphere. Concepts that lasted decades are being revisited due to their puzzling measurements. In this review, I will cover some of these puzzles and what we are learning regarding the dynamic nature of the heliosheath.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127471667","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":"Black Hole Horizons and How They Begin","authors":"D. Brill","doi":"10.1080/21672857.2012.11519694","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519694","url":null,"abstract":"Abstract Properties of black holes are examined that follow from the definition of the horizon as the boundary of the past of null infinity. The beginning of the black hole is defined as the set of spacetime events at which the null geodesics that generate the horizon enter the horizon. This set is spacelike and appears as a crease in the horizon because at least two generators cross at each of its points. The relation between the crease set and future null infinity is that between object and image produced by the gravitational lensing of the collapsing mass-energy. The crease set is not a manifold but has the structure of a tree. Near a vertex the horizon is a cone over a polyhedron.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"389 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114504627","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":"Water on The Moon, II. Origins & Resources","authors":"A. Crotts","doi":"10.1080/21672857.2012.11519695","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519695","url":null,"abstract":"In Part I we recount the history of observation and laboratory measurement culminating with the excavation of water from a permanently shadowed region near the lunar South Pole by the impact of the LCROSS mission in 2009. In this installment we consider what the current data imply about the nature of water and other volatile substances on and in the Moon.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133921100","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 GEM Theory of the Unification of Gravitation and Electro-Magnetism","authors":"J. Brandenburg","doi":"10.1080/21672857.2012.11519696","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519696","url":null,"abstract":"Abstract The GEM (Gravity Electro-Magnetism), theory is presented as an alloy of Sakharov and Kaluza-Klein approaches to field unification. GEM uses the concept ofgravity fields as Poynting fields to postulate that the non-metric portion of the EM stress tensor becomes the metric tensor in strong fields leading to “self-censorship”. Covariant formulation of the GEM theory is accomplished through definition of the spacetime metric tensor as a portion of the EM stress tensor normalized by its own trace: gab = 4 (FcaFcb)/(FabFab), it is found that this results in a massless ground state vacuum and a Newtonian gravitation potential f=. E2/B2 =GM/r, where E, B and F are part of the vacuum Zero Point Fluctuation (ZPF), M and r are the mass and distance from the center of a gravitating body, and G is the Newton gravitation constant. It is found that a Lorentz flat-space metric is recovered in the limit of a vacuum full spectrum ZPF. The vacuum ZPF energy and vacuum quantities G, h, c, gives birth to particles quantities mp, me, e,-e in a process triggered by the appearance of the Kaluza-Klein fifth dimension, where also the EM and gravity forces split from each other in a process correlated to the splitting apart of protons and electrons. The separate appearance of the proton and electron occurs as the splitting of a light-like spacetime interval of zero-length into a finite space-like portion containing three subdimensions identified with the quarks and a time-like portion identified with the electron. The separation of mass with charge for the electron and proton pair comes about from a U(1) symmetry, with a rotation in imaginary angle. A logarithmic variation of charge with mass for the proton-electron pair results in and leads to the formula ln(ro/rp) = s, where s = (mp/me)1/2, where mp and me are the electron and proton masses respectively and where ro =e2/moc2/, and where mo = (mpme)1/2 and where rp is the Planck length. This leads to the formula G=e2/mo 2aexp(-2s)=6.6684x10-11 dynes-cm2/g2, without free parameters, which is within 1 part per thousand of the measured value. We also have from the mass model, where q’/e = a-1/2 is the normalized Planck charge, and where MP is the Planck mass, a formula for the proton mass : mp=MP sq’/e = 1.71 x10-24g and thus is accurate to 2.5%, also without free parameters. GEM theory is now validated through the the Standard Model of physics. Derivation of the value of the Gravitation constant based on the observed variation of a with energy: results in the formula G @ hc/Mhc 2 exp (-1/(1.61a)), where a is the fine structure constant, h, is Plancks constant, c, is the speed of light, and Mhc is the mass of the hcc Charmonium meson, and is shown to be identical to that derived from GEM postulates. GEM is thus consistent with quantum renormalization with an ultraviolet cutoff at the Planck length. More accurate values of G me and mp are found by perturbation theory.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"96 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125161596","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 Interferometrically Derived Sample of Miras with Phase using Spitzer: Paper I – A First Look","authors":"M. Creech-Eakman, T. Güth, D. Luttermoser, C. Jurgenson, A. Speck","doi":"10.1080/21672857.2012.11519693","DOIUrl":"https://doi.org/10.1080/21672857.2012.11519693","url":null,"abstract":"Abstract We show some preliminary 10-37 micron high-resolution spectra taken with the Spitzer Space Telescope in 2008-9 of Mira variables distributed across the M, S and C chemical subclasses. Our entire Spitzer sample of 25 galactic Miras was observed from two to several times during this observing campaign and all have simultaneously measured near-infrared interferometric diameters acquired using the Palomar Testbed Interferometer. Because our sources are very bright for Spitzer IRS (typically 5-100 Janskys), we have excellent signal to noise and for many sources see marked changes in overall flux levels as a function of phase. Further, we are able to identify many strong emission lines and emission features due to silicate and carbon dusts and molecular constituents. We introduce the sample and the design of our experiment, discuss the data reduction required for such bright sources using Spitzer, show several examples of spectra with phase and discuss some preliminary findings. Finally, we discuss future steps for Paper II, to be presented later in the year.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117050254","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":"Water on The Moon, I. Historical Overview","authors":"A. Crotts","doi":"10.1080/21672857.2011.11519687","DOIUrl":"https://doi.org/10.1080/21672857.2011.11519687","url":null,"abstract":"Abstract By mid-19th century, astronomers strongly suspected that the Moon was largely dry and airless, based on the absence of any observable weather. [1] In 1892, William H. Pickering made a series of careful occultation measurements that allowed him to conclude that the lunar surface’s atmospheric pressure was less than 1/4000th of Earth’s. [2] Any number of strange ideas arose to contradict this, including Danish astronomer/mathematician Peter Andreas Hansen’s hypothesis, that the Moon’s center of mass is offset by its center of figure by 59 kilometers, meaning that one or two scale-heights of atmosphere could hide on the far side of the Moon, where it might support water oceans and life. [3] Hans Horbiger’s 1894 Welteislehre (“World Ice”) theory, that the Moon and much of the cosmos is composed of water ice, became the favored cosmology of leaders of Third Reich Germany. [4] Respectable scientists realized that significant amounts of water on the Moon’s surface would rapidly sublime into the vacuum.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114530513","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":"How are Bright Galaxies Embedded within their Dark Matter Halos?","authors":"T. Brainerd","doi":"10.1080/21672857.2011.11519691","DOIUrl":"https://doi.org/10.1080/21672857.2011.11519691","url":null,"abstract":"Abstract Recent studies suggest that the orientations of large, bright galaxies within their dark matter halos are related to the morphologies of the galaxies themselves. Elliptical galaxies tend to be oriented such that, in projection on the sky, the mass (i.e., the dark matter) is well-aligned with the luminous galaxy. On the other hand, disk galaxies tend to be oriented such that their angular momentum vectors are aligned with the angular momenta of their halos. This results in a misalignment of mass and light, and has important implications for future studies that seek to measure the shapes of the dark matter halos that surround disk galaxies.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116425769","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":"Embrace Your Paradoxes","authors":"Scott Tyson","doi":"10.1080/21672857.2011.11519688","DOIUrl":"https://doi.org/10.1080/21672857.2011.11519688","url":null,"abstract":"A Grand Opportunity The universe is not paradoxical. It’s very tempting to assign the “existence” of paradoxes to the universe, but that wouldn’t really be right. After all, paradoxes involving our universe can “exist” in only one place in the universe and that is within the mind of an observer. Indeed, this is also the only place where perceptions, interpretations, and understanding about the universe exclusively reside. So, as tempting as blaming the universe might at first seem for those pesky paradoxes, the paradoxes really arise from the inadequate understanding possessed by observers, meaning us, the science community.","PeriodicalId":204186,"journal":{"name":"Astronomical Review","volume":"61 7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115066499","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}