6,695 research outputs found
An Alternative to Spinning Dust for the Microwave Emission of LPH 201.663+1.643: an Ultracompact HII Region
The microwave spectral energy distribution of the dusty, diffuse H II region
LPH 201.663+1.643 has been interpreted by others as tentative evidence for
microwave emission from spinning dust grains. We present an alternative
interpretation for that particular object; specifically, that an ultracompact H
II region embedded within the dust cloud would explain the available
observations as well or better than spinning dust. Parameters for the size,
surface brightness, and flux density of the putative ultracompact HII region,
derived from the microwave observations, are within known ranges. A possible
candidate for such an ultracompact H II region is IRAS 06337+1051, based upon
its infrared colors. However, IRAS 06337+1051's infrared flux appears to be too
small to be consistent with the microwave flux required for this alternative
model to explain the observations.Comment: 11 pages, 3 figures, accepted to ApJ Letter
Detecting Life-bearing Extra-solar Planets with Space Telescopes
One of the promising methods to search for life on extra-solar planets
(exoplanets) is to detect life's signatures in their atmospheres. Spectra of
exoplanet atmospheres at the modest resolution needed to search for oxygen,
carbon dioxide, water, and methane will demand large collecting areas and large
diameters to capture and isolate the light from planets in the habitable zones
around the stars. For telescopes using coronagraphs to isolate the light from
the planet, each doubling of telescope diameter will increase the available
sample of stars by an order of magnitude, indicating a high scientific return
if the technical difficulties of constructing very large space telescopes can
be overcome. For telescopes detecting atmospheric signatures of transiting
planets, the sample size increases only linearly with diameter, and the
available samples are probably too small to guarantee detection of life-bearing
planets. Using samples of nearby stars suitable for exoplanet searches, this
paper shows that the demands of searching for life with either technique will
require large telescopes, with diameters of order 10m or larger in space.Comment: 15 pages, 6 figures, submitted to Ap.
A simplified instrument for recording and indicating frequency and intensity of icing conditions encountered in flight
Near-surface ocean current sensors : problems and performance
When current meters are used to measure mean horizontal
currents in surface gravity waves, immunity to the vertical
component of flow is important, even though the net vertical
flow averages to zero and is normal to the desired horizontal
components. A technique is presented for estimating the
magnitude of the errors introduced by imperfect rejection of
the off-axis flows (cross-talk) from laboratory measurements of
the current meter "vertical-cosine-response." The predicted
dynamic response is shown to compare favorably with laboratory
measurements. The measured steady state vertical-cosine-response
functions for several practical current sensors are
summarized and used to estimate the magnitude of wave-induced
errors in horizontal mean current measurements. A new dye
technique for evaluating near-surface current meter performance
in waves is shown.Prepared for the Working Con6enence on
CURRENT MEASUREMENTS sponsored by the
NOAA 0ffice of Ocean Engineering with
the Delaware Sea Grant College Program
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