On interstellar reddening law in the Taurus dark clouds

The interstellar reddening law in the Taurus dark clouds is investigated from visual, infrared, and ground based ultraviolet photometric observations of heavily reddened stars HD 29647, HDE 283701, and HDE 283812. The star HD 29647 located in the center of a very dense dark cloud Khavtassi 278 shows a reddening law which is anomalous in the wavelengths shorter than 400 nm. When combined with observations by Snow and Seab from the IUE it can be represented by a single straight line from 1 m to 250 nm. Other two stars situated in less dense parts of the Taurus dark clouds show normal reddening law.     

Infrared photometry of periodic comets Encke,Chernykh, Kearns-Kwee,Stephan-Oterma,and Tuttle

Nearly simultaneous photometry of the reflected and thermal infrared spectra of periodic comets Encke, Chernykh, Kearns-Kwee, Stephan-Oterma, and Tuttle are presented. The 10-μm, silicate emission feature has been detected for the first time in periodic comets and was observed in three of these objects. The albedo of the dust particles in the comae of these comets is calculted and compared to that of Comet Kohoutek. The peculiar behavior of the dust in Comet Encke is discussed.     

Thermal properties of 433 Eros

We report on radiometric and reflected light observations of 433 Eros at high time resolution, high accuracy, and broad spectral coverage. We use a thermal inertia model to estimate the thermal inertia, albedo, and size of Eros. We find an albedo of 0.125 ± 0.025 with axes of 39.3 ± 2.0 × 16.1 ± 0.8 km. Our estimate of the albedo is about 30% lower than previous estimates.     

Circulation of shelf waters in the KwaZulu-Natal Bight,South Africa

Ship-based acoustic Doppler current profiler (S-ADCP) technology, used in survey mode, has enabled near- synoptic views of the in situ 3-D current field in the KwaZulu-Natal (KZN) Bight to be elucidated for the first time. Data acquired by the research vessels RS Africana and RS Algoa in June 2005, September 2007, March 2009 and July 2010 are presented. Each S-ADCP dataset showed similar circulation characteristics whereby the continental slope and outer shelf of the KZN Bight were strongly influenced by the south-westward flowing Agulhas Current. This was particularly evident in the extreme north between Cape St Lucia and Richards Bay where the shelf is narrowest and velocities exceeded 200 cm s?1. The widening of the bight to the south moves the Agulhas Current further from the coast, resulting in a diminishing velocity gradient on the outer shelf which terminates around the midshelf axis. The southern region of the bight was mostly influenced by the Durban cyclonic eddy (Durban Eddy), and in June 2005 and September 2007, by a cyclonic ‘swirl’ that occupied the entire southern half of the KZN Bight, the latter identified by a combination of S-ADCP-, satellite-derived SST- and ocean colour data. Satellite data showed low-chlorophyll offshore water to move into this swirl and northwards along the inner- and midshelf, reaching the Thukela River. Inner-shelf circulation north of the Thukela River was weak (<20 cm s?1) and highly variable. Satellite-tracked surface drogues deployed in the Durban Eddy found their way into the northward coastal current in the KZN Bight, with velocities exceeding 90 cm s?1 at times. The drogues also highlighted the strong influence of wind, especially in the northern bight between Durnford Point and Cape St Lucia, with residence times on the shelf exceeding 14 days, suggesting this region to be of biological importance particularly for recruitment.     

Describing gonad development and gametogenesis in southern Africa’s endemic box jellyfish Carybdea branchi (Cubozoa,Carybdeidae)

Information on the reproductive development of species of box jellyfish (class Cubozoa) is poor globally, despite their significance as potent stingers and worrying projections about range expansions. While most species are confined to tropical and subtropical waters, the South African box jellyfish Carybdea branchi is commonly found in the cold-water (especially southern) Benguela ecosystem. Its biology is unknown. Here, we examine reproductive development and describe gametogenesis in this dioecious species. Four and five maturity classes were determined for males and females, respectively, as well as five oocyte developmental stages. Oocyte sizes differed significantly between developmental stages. Mature and immature medusae differed significantly in size, but males and females did not. Individuals matured at approximately 30 mm average bell dimensions. Carybdea branchi displayed gonadal development characteristic of a semelparous organism.     

Surface composition of Pluto

Infrared photometric observations (1–4 μm) of Pluto have been made using broadband (Δλ/λ ～ 0.3) and narrowband (Δλ/λ ～ 0.05–0.1) filters. We confirm the probable presence of methane in some form, though, in detail the match between the spectrum of Pluto and the laboratory spectrum of methane frost is poor.     

Structure of Saturn's Mesosphere from the 28 Sgr Occultations

We analyze an extensive data set of immersion and emersion lightcurves of the occultation of 28 Sgr by Saturn's atmosphere on 3 July 1989. The data give profiles of number density as a function of altitude at a variety of latitudes, at pressures ranging from about 0.5 to about 20 μbar. The atmosphere is essentially isothermal in this range, with a temperature close to 140 K for an assumed mean molecular weight of 2.135. Owing to favorable ring geometry, an accurate radial scale is available for all observations, and we confirm the substantial equatorial bulge produced by zonal winds of ∼450 m/s first observed in the Voyager radio-occultation experiments. The fact that the bulge is still present at microbar pressures suggests that the equatorial winds persist to high altitudes. According to our radial scale, the 2.4-μbar level, which corresponds to half-flux in the stellar occultations, is at an equatorial radius of 60,960 km. This radial scale is in good agreement with the Voyager radio-occultation data at mbar pressures and allows smooth interpolation of the isothermal structure between the stellar-occultation and radio-occultation regions. We do not have such a smooth interpolation between our data and Voyager ultraviolet occultation data, unless we discard the lowest 200 km of Voyager ultraviolet data. When this is done, we obtain a complete atmospheric model from an equatorial radius of 61,500 km down to an equatorial radius of 60,500 km. This model gives excellent agreement between all 28 Sgr, Voyager, and Pioneer 11 data.     

The 1.7- to 4.2-μm spectrum of asteroid 1 Ceres: Evidence for structural water in clay minerals

A high-resolution Fourier spectrum (1.7–3.5 μm) and medium-resolution spectrophotometry (2.7–4.2 μm) were obtained for Asteroid 1 Ceres. The presence of the 3-μm absorption feature due to water of hydration was confirmed. The 3-μm feature is compared with the 3-μm bands due to water of hydration in clays and salts. It is concluded that the spectrum of Ceres shows a strong absorption at 2.7–2.8 μm due to structural OH groups in clay minerals. The dominant minerals on the surface of Ceres are therefore hydrated clay minerals structurally similar to terrestrial montmorillonites. There is also a narrow absorption feature at 3.1 μm which is attributable to a very small amount of water ice on Ceres. This is the first evidence for ice on the surface of an asteroid.     

10 μm polarimetry of ceres

Linear polarimetry of Ceres at 10 μm is presented. These data represent the first published polarization measurements of an asteroid in the thermal infrared. It is found that Ceres is polarized at the 0.2-0.6% level. This data set is compared with theoretical models of the linear polarization of emitted radiation from a spherical plane. These models are used to derive the pole position and thermal inertia of Ceres. Ceres is best fit with a thermal inertia of $\text{0.0010±0.0003}\text{cal}\text{cm}{}^{\mathrm{?2}}\text{°}\text{K}{}^{\mathrm{?1}}\text{sec}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and a pole orientation of β_p = 36° ± 5°, λ_p = 270° ± 3°. It is concluded that 10μm polarimetry is a potentially powerful technique for remotely sensing the pole orientation and thermal inertia of asteroids.