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Impact Debris Particles in Jupiter's Stratosphere

West, Robert A.; Baines, Kevin H.; Karkoschka, Erich +3 more

The aftermath of the impacts of periodic comet Shoemaker-Levy 9 on Jupiter was studied with the Wide Field Planetary Camera 2 on the Hubble Space Telescope. The impact debris particles may owe their dark brown color to organic material rich in sulfur and nitrogen. The total volume of aerosol 1 day after the last impact is equal to the volume of a …

Parallaxes and the Hertzsprung-Russell diagram for the preliminary HIPPARCOS solution H30

Grewing, M.; Evans, D. W.; Lindegren, L. +20 more

We outline the principles by which absolute trigonometric parallaxes have been derived from the first 30 months of data acquired by the Hipparcos astrometry satellite. Distributions of the parallaxes and formal errors of more than one hundred thousand stars are presented, indicating median standard errors of about 1.5milliarcsec (mas). Tests which…

The Hubble Space Telescope (HST) Observing Campaign on Comet Shoemaker- Levy 9

Stern, S. A.; Feldman, P. D.; Lamy, P. +18 more

The Hubble Space Telescope made systematic observations of the split comet P/Shoemaker-Levy 9 (SL9) (P designates a periodic comet) starting in July 1993 and continuing through mid-July 1994 when the fragments plunged into Jupiter's atmosphere. Deconvolutions of Wide Field Planetary Camera images indicate that the diameters of some fragments may h…

The Polarization and Ultraviolet Spectrum of Markarian 231

Schmidt, Gary D.; Smith, Paul S.; Allen, Richard G. +1 more

Ultraviolet spectropolarimetry acquired with the Hubble Space Telescope of the peculiar Seyfert galaxy Mrk 231 is combined with new high-quality ground-based measurements to provide the first, nearly complete, record of its linear polarization from 1575 to 7900 A. The accompanying ultraviolet spectrum portrays the heavily extinguished emission-lin…

An ultraviolet flare at the centre of the elliptical galaxy NGC4552

Cappellari, Michele; Renzini, Alvio; Greggio, Laura +3 more

MOST present-day galaxies are not 'active', in that they show no signs of continuing, high-energy events. The high energy output of an active galaxy is usually attributed to accretion of gas onto a massive black hole at its centre. Yet it remains an open question whether such black holes might exist at the centre of most large galaxies, and be und…

Interpretation and consequences of large-scale magnetic variances observed at high heliographic latitude

Horbury, T. S.; Smith, E. J.; Giacalone, J. +2 more

We consider recent Ulysses observations of the large-scale variances in the transverse components of the interplanetary magnetic field. A previously-suggested theory is shown to provide a good fit to the observed spatial variation and level of the fluctuations. The transport of cosmic rays in the heliosphere will be significantly affected by these…

Spectroscopic Identification of Probable Cataclysmic Variables in the Globular Cluster NGC 6397

Cohn, H. N.; Lugger, P. M.; Cool, A. M. +3 more

The existence of compact binaries in dense clusters is of considerable interest for testing theories of binary production and evolution, as well as the dynamical evolution and survival of the clusters in which they reside. Here, using the newly repaired Hubble Space Telescope to observe the collapsed core of the nearby globular cluster NGC 6397, w…

Hubble Space Telescope Images of Nearby Luminous Quasars. II. Results for Eight Quasars and Tests of the Detection Sensitivity

Schneider, Donald P.; Bahcall, John N.; Kirhakos, Sofia

Observations with the Wide-Field Camera of the Hubble Space Telescope (HST) are presented for eight intrinsically luminous quasars with redshifts between 0.16 and 0.29. These observations, when combined with a similar HST study of the quasar PKS 2349-014, show that luminous nearby quasars exist in a variety of environments.

Seven companion ga…

Galactic wind and Lyman α emission in the blue compact galaxy Haro 2 = MKN 33.

Mas-Hesse, J. M.; Kunth, D.; Sargent, W. L. W. +1 more

We have observed with the Goddard High-Resolution Spectrometer on board the Hubble Space Telescope the blue compact galaxy Haro 2 in two wavelength regions around Lyman α and O I 1302A. We have detected redshifted absorptions in those lines as well as in lines of N I, Si II and Si III, in front of the hot stars ionizing the central H II region of …

The Geometry and Kinematics of the Broad-Line Region in NGC 5548 from HST and IUE Observations

Peterson, Bradley M.; Shields, Joseph C.; Pogge, Richard W. +6 more

The spatial and radial velocity distribution of broad-line--emitting gas in the Seyfert 1 galaxy NGC 5548 is examined through the process of reverberation mapping, which is done by detailed comparison of continuum and emission-line variations. Recent spectroscopic monitoring of NGC 5548 with HST and IUE allows us to resolve the "transfer function"…