The Principles of Aesthetics. By Dewitt H. Parker

Shapley, Fern Rusk

doi:10.1080/00043079.1921.11409711

Cited by 26 publications

(29 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Astrometric data collected by the founders of modern astronomy revealed that both the Sun and stars are moving through space (Herschel 1783), 17 and led to the recognition that the Sun encounters interstellar clouds during its journey through space (Shapley 1921). Because both the Sun and interstellar clouds move through space, the Doppler contribution of solar motion to the heliocentric interstellar velocities must be removed for comparisons between kinematically defined clouds and spatially defined objects such as Loop I.…”

Section: Appendix D Bulk Motion Of Local Interstellar Clouds Relativementioning

confidence: 99%

CHARTING THE INTERSTELLAR MAGNETIC FIELD CAUSING THEINTERSTELLAR BOUNDARY EXPLORER(IBEX) RIBBON OF ENERGETIC NEUTRAL ATOMS

Frisch

Berdyugin

Piirola

et al. 2015

ApJ

View full text Add to dashboard Cite

The interstellar magnetic field (ISMF) near the heliosphere is a fundamental component of the solar galactic environment that can only be studied using polarized starlight. The results of an ongoing survey of the linear polarizations of local stars are analyzed with the goal of linking the ISMF that shapes the heliosphere to the nearby field in interstellar space. We present new results on the direction of the magnetic field within 40 pc obtained from analyzing polarization data using a merit function that determines the field direction that provides the best fit to the polarization data. Multiple magnetic components are identified, including a dominant interstellar field, B POL , that is aligned with the direction ℓ, b = 36°.2, 49°.0 (±16°.0). Stars tracing B POL have the same mean distance as stars that do not trace B POL , but show weaker average polarizations consistent with a smaller column density of polarizing material. B POL is aligned with the ISMF traced by the IBEX Ribbon to within 7.6 7.6 14.9 -+ degrees. The variations in the polarization position angle directions derived from the data that best match B POL indicate a low level of magnetic turbulence, ∼9°±1°. The direction of B POL is obtained after excluding polarization data tracing a separate magnetic structure that appears to be associated with interstellar dust deflected around the heliosphere. The velocities of local interstellar clouds relative to the Local Standard of Rest (LSR) increase with the angles between the LSR velocities and B POL , indicating that the kinematics of local interstellar material is ordered by the ISMF. The Loop I superbubble that extends close to the Sun contains dust that reddens starlight and whose distance is determined by the color excess E(B − V) of starlight. Polarizations caused by grains aligned with respect to B POL are consistent with the location of the Sun in the rim of the Loop I superbubble. An angle of 76.8 27.6 23.5 -+ between B POL and the bulk LSR velocity the local interstellar material indicates a geometry that is consistent with an expanding superbubble. The efficiency of grain alignment in the local interstellar medium has been assessed using stars where both polarization data and hydrogen column density data are available. Nearby stars appear to have larger polarizations than expected based on reddened sightlines, which is consistent with previous results, but uncertainties are large. Optical polarization and color excess E(B − V) data indicate the presence of nearby interstellar dust in the BICEP2 field. Color excess E(B − V) indicates an optical extinction of A V >0.6 in the BICEP2 field, while the polarization data indicate that A V >0.09 mag. The IBEX Ribbon ISMF extends to the boundaries of the BICEP2 region.

show abstract

Section: Appendix D Bulk Motion Of Local Interstellar Clouds Relativementioning

confidence: 99%

CHARTING THE INTERSTELLAR MAGNETIC FIELD CAUSING THEINTERSTELLAR BOUNDARY EXPLORER(IBEX) RIBBON OF ENERGETIC NEUTRAL ATOMS

Frisch

Berdyugin

Piirola

et al. 2015

ApJ

View full text Add to dashboard Cite

show abstract

“…The fact that such regions were a common occurrence in the Milky Way was clear in the early years of 1900, with the systematic observations of Barnard, as was stated in a textbook of the time (Clerke 1903), and it began to be hypothesised that they were not actually holes in the fabric of the sky, but instead might be "obscured" by some intervening material. For some decades, this hypothesis was the topic of some heated debates, some of which are on record in the proceedings of academic meetings of the time (Shapley & Curtis 1921). It was only about in 1930 that firm evidence of interstellar extinction became available (Trumpler 1930).…”

Section: Interstellar Extinction Before Pahsmentioning

confidence: 99%

Polycyclic Aromatic Hydrocarbons and the Extinction Curve

Mulas

Malloci

Joblin

et al. 2011

EAS Publications Series

View full text Add to dashboard Cite

Abstract. Aromatic carbon, in some form, has been an essential ingredient by and large in all models of the extinction curve, since the original proposal to attribute the bump at 217.5 nm to "astronomical graphite". This aromatic carbon is most naturally identified, in up to date models, with a population of Polycyclic Aromatic Hydrocarbons (PAHs), free and/or clustered. In all models, this PAH population accounts for the far-UV nonlinear rise in the extinction curve, contributes to the bump and possibly part of the large set of unidentified, discrete absorption features in the visible (the Diffuse Interstellar Bands). We review the current state of our understanding of the contribution of PAHs to interstellar extinction, and what constraints can be imposed on the PAH population by fitting extinction models to observations.

show abstract

“…Seventy-six years ago Curtis (1921) and Shapley(1921) met in this auditorium to present their differing views on the nature of the nebulae. Shapley believed that our Milky Way galaxy was a vast continent surrounded by small island nebulae.…”

Section: Introductionmentioning

confidence: 99%

Extra-galactic Distance Scale

Bergh

1970

Nature

View full text Add to dashboard Cite

Cepheid variables are used to derive a Virgo cluster distance of 16.0 ± 1.5Mpc. In conjunction with the Coma velocity and the well-established Coma/Virgo distance ratio, this yields a Hubble parameter H = 81 ± 8 km s o -1Mpc . By combining this value with an age of the Universe / 16.8 ± 2.1 Gyr, that -1 is derived from the metal-poor globular cluster M92, one obtains f (5, %) / 1.39 ± 0.22. This value is only marginally consistent with an Einstein-de Sitter universe with 5 = 0 and % = 0, which has f = 1. An Einstein-de Sitter universe with 5 = 1 and % = 0, for which f = > , appears to be excluded at the 3. level. It is shown that some recent small values of H resulted from the large intrinsic dispersion in o the linear diameters of galaxies, and from the fact that well-observed supernovae of Type Ia exhibit a luminosity range of ~30 at maximum light.-3 - INTRODUCTIONSeventy-six years ago Curtis (1921) and Shapley(1921) perhaps more interesting) world. AGE CONSTRAINTS ON THE HUBBLE PARAMETERThe age of the Universe cannot be smaller than that of the oldest stars.The ages of the oldest star clusters therefore place severe constraints on the The age of an expanding universe may be expressed in the form observations of the extragalactic distance scale can place severe constraints on permissible models of the Universe. THE DISTANCE SCALEGalaxies are exceedingly distant. Standard Candles in them are therefore dim and difficult to observe. As a consequence of this, determination of the extragalactic distance scale is a very difficult enterprise that challenges the utmost limits of our observational capabilities. "There, we measure shadows, and search among ghostly errors of measurement for landmarks that are scarcely more substantial" (Hubble 1936).We now know that the first attempt by Hubble & Humason (1931) ARE SNe Ia GOOD STANDARD CANDLES?Supernovae of Type I were first used as standard candles by Kowal (1968). Recently van den Bergh (1996) has determined the values of M (max) for B all supernovae of Type Ia for which Cepheid distances are known. These data are collected in Table 2. This table shows that well-observed supernovae of Type Ia exhibit a range of ~30 in luminosity at maximum light. This result clearly places the usefulness of SNe Ia as calibrators of the extragalactic distance scale in doubt.The data in Table 2 appear to confirm the suspicion that SNe Ia in late-type galaxies are, on average, more luminous that those in E and S0 galaxies (or in the nuclear bulges of spirals). However, a striking exception to this rule is provided by 19.43 ± 0.22. Possibly, this high luminosity is due to the fact that SN 1994D had a relatively young progenitor that was associated with the prominent dust lane in NGC 4526. GALAXY DIAMETERS AS STANDARD METER STICKSSandage ( are, however, a number of reasons for questioning the legitimacy of this technique for determining extragalactic distances: Van den Bergh (1992) showed KPNO 4-m telescope images, printed to the same linear scale, of the Sc I galaxies NGC 309 in...

show abstract

The Principles of Aesthetics. By Dewitt H. Parker

Cited by 26 publications

References 0 publications

CHARTING THE INTERSTELLAR MAGNETIC FIELD CAUSING THEINTERSTELLAR BOUNDARY EXPLORER(IBEX) RIBBON OF ENERGETIC NEUTRAL ATOMS

CHARTING THE INTERSTELLAR MAGNETIC FIELD CAUSING THEINTERSTELLAR BOUNDARY EXPLORER(IBEX) RIBBON OF ENERGETIC NEUTRAL ATOMS

Polycyclic Aromatic Hydrocarbons and the Extinction Curve

Extra-galactic Distance Scale

Contact Info

Product

Resources

About