منابع مشابه
Accuracy/Precision of USNO Predicted Clock Estimates for GPS Satellites
The United States Naval Observatory (USNO) Earth Orientation Department GPS Analysis Division (GPSAD) processes data from hundreds of GNSS receivers daily, computing multiple GNSS carrierphase-based product sets 365 days/year. Quantities estimated typically include high-precision (1-3 cm) GNSS satellite orbits/clock corrections, receiver clock corrections, station coordinates, earth-orientation...
متن کاملCOMPOSITIONAL DIVERSITY IN THE ATMOSPHERES OF HOT NEPTUNES, WITH APPLICATION TO GJ 436b
Neptune-sized extrasolar planets that orbit relatively close to their host stars — often called “hot Neptunes” — are common within the known population of exoplanets and planetary candidates. Similar to our own Uranus and Neptune, inefficient accretion of nebular gas is expected produce hot Neptunes whose masses are dominated by elements heavier than hydrogen and helium. At high atmospheric met...
متن کاملNeptunes Visual Albedo Variations Over a Solar Cycle A PreVoyager Look at IonInduced Nucleatlon and Cloud Formation in Neptunes Troposphere
High-energy galactic cosmic rays'can penetrate to deep levels within Neptune's atmosphere to form a substantial ionospheric layer in the lower stratosphere and upper troposphere of the planet. Because cosmic-ray modulation in the interplanetary medium creates an inverse relationship between cosmic-ray intensity and solar activity, the ionization rate in the lower atmosphere will vary with the I...
متن کاملThe HD 40307 Planetary System: Super-Earths or Mini-Neptunes?
Three planets with minimum masses less than 10 M⊕ orbit the star HD 40307, suggesting these planets may be rocky. However, with only radial velocity data, it is impossible to determine if these planets are rocky or gaseous. Here we exploit various dynamical features of the system in order to assess the physical properties of the planets. Observations allow for circular orbits, but a numerical i...
متن کاملFormation and Structure of Low-Density Exo-Neptunes
Kepler has found hundreds of Neptune-size (2–6R⊕) planet candidates within 0.5 AU of their stars. The nature of the vast majority of these planets is not known because their masses have not been measured. Using theoretical models of planet formation, evolution, and structure, we explore the range of minimum plausible masses for lowdensity exo-Neptunes. We focus on highly irradiated planets with...
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ژورنال
عنوان ژورنال: Nature
سال: 1989
ISSN: 0028-0836,1476-4687
DOI: 10.1038/340673a0