1,551 research outputs found
Dynamics and Spatial Distribution of Global Nighttime Lights
Using open source data, we observe the fascinating dynamics of nighttime
light. Following a global economic regime shift, the planetary center of light
can be seen moving eastwards at a pace of about 60 km per year. Introducing
spatial light Gini coefficients, we find a universal pattern of human
settlements across different countries and see a global centralization of
light. Observing 160 different countries we document the expansion of
developing countries, the growth of new agglomerations, the regression in
countries suffering from demographic decline and the success of light pollution
abatement programs in western countries
Ruedi Graf, Die Tagebücher des Pfarrers Diethelm Schweizer (1751–1824), 2010
No abstract availabl
A Circumstellar Disc in a High-Mass Star Forming Region
We present an edge-on Keplerian disc model to explain the main component of
the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1 N.
The brightness distribution and spectrum of the line of bright masers are
successfully modeled with high amplification of background radio continuum
emission along velocity coherent paths through a maser disc. The bend seen in
the position-velocity diagram is a characteristic signature of differentially
rotating discs. For a central mass of 30 solar masses, suggested by other
observations, our model fixes the masing disc to have inner and outer radii of
about 350 AU and 1000 AU.Comment: 11 pages, accepted for publication in ApJ Letter
Trigonometric Parallaxes of Massive Star Forming Regions: II. Cep A & NGC 7538
We report trigonometric parallaxes for the sources NGC 7538 and Cep A,
corresponding to distances of 2.65 [+0.12/-0.11] kpc and 0.70 [+0.04/-0.04]
kpc, respectively. The distance to NGC 7538 is considerably smaller than its
kinematic distance and places it in the Perseus spiral arm. The distance to Cep
A is also smaller than its kinematic distance and places it in the Local arm or
spur. Combining the distance and proper motions with observed radial velocities
gives the location and full space motion of the star forming regions. We find
significant deviations from circular Galactic orbits for these sources: both
sources show large peculiar motions (> 10 km/s) counter to Galactic rotation
and NGC 7538 has a comparable peculiar motion toward the Galactic center.Comment: 21 pages, 8 figures; to appear in the Astrophysical Journa
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