2,459 research outputs found
The Interiors of Giant Planets: Models and Outstanding Questions
We know that giant planets played a crucial role in the making of our Solar
System. The discovery of giant planets orbiting other stars is a formidable
opportunity to learn more about these objects, what is their composition, how
various processes influence their structure and evolution, and most importantly
how they form. Jupiter, Saturn, Uranus and Neptune can be studied in detail,
mostly from close spacecraft flybys. We can infer that they are all enriched in
heavy elements compared to the Sun, with the relative global enrichments
increasing with distance to the Sun. We can also infer that they possess dense
cores of varied masses. The intercomparison of presently caracterised
extrasolar giant planets show that they are also mainly made of hydrogen and
helium, but that they either have significantly different amounts of heavy
elements, or have had different orbital evolutions, or both. Hence, many
questions remain and are to be answered for significant progresses on the
origins of planets.Comment: 43 pages, 11 figures, 3 tables. To appear in Annual Review of Earth
and Planetary Sciences, vol 33, (2005
Caltech Faint Field Galaxy Redshift Survey IX: Source detection and photometry in the Hubble Deep Field Region
Detection and photometry of sources in the U_n, G, R, and K_s bands in a 9x9
arcmin^2 region of the sky, centered on the Hubble Deep Field, are described.
The data permit construction of complete photometric catalogs to roughly
U_n=25, G=26, R=25.5 and K_s=20 mag, and significant photometric measurements
somewhat fainter. The galaxy number density is 1.3x10^5 deg^{-2} to R=25.0 mag.
Galaxy number counts have slopes dlog N/dm=0.42, 0.33, 0.27 and 0.31 in the
U_n, G, R and K_s bands, consistent with previous studies and the trend that
fainter galaxies are, on average, bluer. Galaxy catalogs selected in the R and
K_s bands are presented, containing 3607 and 488 sources, in field areas of
74.8 and 59.4 arcmin^2, to R=25.5 and and K_s=20 mag.Comment: Accepted for publication in ApJS; some tables and slightly nicer
figures available at http://www.sns.ias.edu/~hogg/deep
Test results of Spacelab 2 infrared telescope focal plane
The small helium cooled infrared telescope for Spacelab 2 is designed for sensitive mapping of extended, low-surface-brightness celestial sources as well as highly sensitive investigations of the shuttle contamination environment (FPA) for this mission is described as well as the design for a thermally isolated, self-heated J-FET transimpedance amplifier. This amplifier is Johnson noise limited for feedback resistances from less than 10 to the 8th power Omega to greater than 2 x 10 to the 10th power Omega at T = 4.2K. Work on the focal plane array is complete. Performance testing for qualification of the flight hardware is discussed, and results are presented. All infrared data channels are measured to be background limited by the expected level of zodiacal emission
AVHRR and VISSR satellite instrument calibration results for both Cirrus and marine stratocumulus IFO periods
Accurate characterizations of some cloud parameters are dependent upon the absolute accuracy of satellite radiance measurements. Visible wavelength measurements from both the AVHRR and VISSR instruments are often used to study cloud characteristics. Both of these instruments were radiometrically calibrated prior to launch, but neither has an onboard device to monitor degradation after launch. During the FIRE/SRB cirrus Intensive Field Operation (IFO), a special effort was made to monitor calibration of these two instruments onboard the NOAA-9 and GOES-6 spacecraft. In addition, several research groups have combined their efforts to assess the long-term performance of both instruments. These results are presented, and a limited comparison is made with the ERBE calibration standard
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Scientific rationale of a Saturn probe mission
We describe the main scientific goals to be addressed by future in situ exploration of Saturn
MIPS: The Multiband Imaging Photometer for SIRTF
The Multiband Imaging Photometer for SIRTF (MIPS) is to be designed to reach as closely as possible the fundamental sensitivity and angular resolution limits for SIRTF over the 3 to 700μm spectral region. It will use high performance photoconductive detectors from 3 to 200μm with integrating JFET amplifiers. From 200 to 700μm, the MIPS will use a bolometer cooled by an adiabatic demagnetization refrigerator. Over much of its operating range, the MIPS will make possible observations at and beyond the conventional Rayleigh diffraction limit of angular resolution
Adaptive Optics Images of Kepler Objects of Interest
All transiting planets are at risk of contamination by blends with nearby,
unresolved stars. Blends dilute the transit signal, causing the planet to
appear smaller than it really is, or produce a false positive detection when
the target star is blended with eclipsing binary stars. This paper reports on
high spatial-resolution adaptive optics images of 90 Kepler planetary
candidates. Companion stars are detected as close as 0.1 arcsec from the target
star. Images were taken in the near-infrared (J and Ks bands) with ARIES on the
MMT and PHARO on the Palomar Hale 200-inch. Most objects (60%) have at least
one star within 6 arcsec separation and a magnitude difference of 9. Eighteen
objects (20%) have at least one companion within 2 arcsec of the target star; 6
companions (7%) are closer than 0.5 arcsec. Most of these companions were
previously unknown, and the associated planetary candidates should receive
additional scrutiny. Limits are placed on the presence of additional companions
for every system observed, which can be used to validate planets statistically
using the BLENDER method. Validation is particularly critical for low-mass,
potentially Earth-like worlds, which are not detectable with current-generation
radial velocity techniques. High-resolution images are thus a crucial component
of any transit follow-up program.Comment: 9 pages, 4 figures, accepted to A
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