249 research outputs found
Interferometry meets the third and fourth dimensions in galaxies
Radio astronomy began with one array (Jansky's) and one paraboloid of
revolution (Reber's) as collecting areas and has now reached the point where a
large number of facilities are arrays of paraboloids, each of which would have
looked enormous to Reber in 1932. In the process, interferometry has
contributed to the counting of radio sources, establishing superluminal
velocities in AGN jets, mapping of sources from the bipolar cow shape on up to
full grey-scale and colored images, determining spectral energy distributions
requiring non-thermal emission processes, and much else. The process has not
been free of competition and controversy, at least partly because it is just a
little difficult to understand how earth-rotation, aperture-synthesis
interferometry works. Some very important results, for instance the mapping of
HI in the Milky Way to reveal spiral arms, warping, and flaring, actually came
from single moderate-sized paraboloids. The entry of China into the radio
astronomy community has given large (40-110 meter) paraboloids a new lease on
life.Comment: Virginia Trimble 2014, in IAU Symp. 309 "Galaxy in 3D across the
Universe", B.L. Ziegler, F. Combes, H. Dannerbauer, M. Verdugo, Eds.
(Cambridge: Cambridge Uni. Press) in press NOTE - Should be "Galaxies" not
"Galaxy
Star Formation from Spitzer (Lyman) to Spitzer (Space Telescope) and Beyond
A summary of JENAM 2008 Symposium 9 "Star Formation from Spitzer (Lyman) to
Spitzer (Space Telescope) and Beyond", held in Vienna, 10-12 September 2008.Comment: 6 page
A citation history of measurements of Newtons constant of Gravity
We created and analyzed a citation history of papers covering measurements of
Newtons constant of gravity from 1686 to 2016. Interest concerning the true
value of the gravitational constant was most intense in the late 90s to early
2000s and is gaining traction again in the present. Another network consisting
of the same papers was created using citations from databases to display the
prominence of papers on Newtons constant in the wider scientific community. In
general, papers that were important in one network remained important in the
other while papers that had little importance in one network remained
unimportant in the other. The US contributes the most to literature on the
topic both in where journals were published and where the work was done;
however, many other countries, such as China, Russia, France, Germany,
Switzerland, and the UK also provide many papers on Newtons G. Work done within
certain countries tends to be considered more important and cited more often
within that country. Recent efforts promoting international collaboration may
have an impact on this trend
The quest for collapsed/frozen stars in single-line spectroscopic binary systems
Black holes are now commonplace, among the stars, in Galactic centers, and
perhaps other places. But within living memory, their very existence was
doubted by many, and few chose to look for them. Zeldovich and Guseinov were
first, followed by Trimble and Thorne, using a method that would have
identified HDE 226868 as a plausible candidate, if it had been in the 1968
catalogue of spectroscopic binaries. That it was not arose from an unhappy
accident in the observing program of Daniel M. Popper long before the discovery
of X-ray binaries and the identification of Cygnus X-1 with that hot, massive
star and its collapsed companion.Comment: Key Words: Black holes, collapsed stars, Cygnus X-1, HDE 226868,
spectroscopic binaries Journal: The Zeldovich Universe Genesis and Growth of
the Cosmic Web IAU Symposium 308, 23-28 June 2014, Tallinn, Estonia)
http://iau.maido.ee/proceeding
Some Faint Stars and a Bright One
The low-luminosity stars are a wild assortment - hot and cool, old and young, dense and diffuse - almost as motley a crew as the 85 astronomers who gathered at Caltech on October 15-16, 1984 to discuss them and to honor the 75th birthday of Jesse L. Greenstein
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