Search Publications

Evidence for Dust Grain Growth in Young Circumstellar Disks

Throop, Henry B.; Bally, John; Esposito, Larry W. +1 more

Hundreds of circumstellar disks in the Orion nebula are being rapidly destroyed by the intense ultraviolet radiation produced by nearby bright stars. These young, million-year-old disks may not survive long enough to form planetary systems. Nevertheless, the first stage of planet formation-the growth of dust grains into larger particles-may have b…

Imaging and Photometry of Comet C/1999 S4 (LINEAR) Before Perihelion and After Breakup

Woodney, Laura M.; Schleicher, David G.; Farnham, Tony L. +3 more

We analyzed photometric measurements and images of comet C/LINEAR before perihelion and after its breakup. Results from our photometry data include a lower limit of 0.44 kilometer for the radius of the nucleus before breakup, and a determination that it was depleted in carbon-chain molecules relative to most other comets. Our imaging and modeling …

Water Production of Comet C/1999 S4 (LINEAR) Observed with the SWAN Instrument

Bertaux, Jean-Loup; Combi, Michael R.; Mäkinen, J. Teemu T. +1 more

The SWAN (Solar Wind ANisotropies) Lyman-alpha all-sky camera on the SOHO spacecraft observed the hydrogen coma of comet C/1999 S4 (LINEAR) from the end of May through mid-August 2000. A systematic set of water-production rates was obtained for this well-documented event of complete fragmentation of a cometary nucleus. The observations indicate th…

Dynamic Variations at the Base of the Solar Convection Zone

Thompson, M. J.; Howe, R.; Hill, F. +5 more

We have detected changes in the rotation of the sun near the base of its convective envelope, including a prominent variation with a period of 1.3 years at low latitudes. Such helioseismic probing of the deep solar interior has been enabled by nearly continuous observation of its oscillation modes with two complementary experiments. Inversion of t…

Discovery of Gaseous S₂ in Io's Pele Plume

Ballester, Gilda E.; McGrath, Melissa A.; Spencer, John R. +2 more

Spectroscopy of Io's Pele plume against Jupiter by the Hubble Space Telescope in October 1999 revealed absorption due to S₂ gas, with a column density of 1.0 +/- 0.2 × 10¹⁶ per square centimeter, and probably also SO₂ gas with a column density of 7 +/- 3 × 10¹⁶ per square centimeter. This SO₂/…

Seismic Images of the Far Side of the Sun

Braun, D. C.; Lindsey, C.

Images of an active region on the far side of the sun were derived by applying seismic holography to recent helioseismic observations from space. Active regions are the centers of energetic phenomena such as solar flares and coronal mass ejections, whose resulting electromagnetic and particle radiation interfere with telecommunications and power t…

Windows Through the Dusty Disks Surrounding the Youngest Low-Mass Protostellar Objects

Cernicharo, J.; González-Alfonso, E.; Noriega-Crespo, A. +5 more

The formation and evolution of young low-mass stars are characterized by important processes of mass loss and accretion occurring in the innermost regions of their placentary circumstellar disks. Because of the large obscuration of these disks at optical and infrared wavelengths in the early protostellar stages (class 0 sources), they were previou…

Solar Wind Outflow and the Chromospheric Magnetic Network

Dammasch, Ingolf E.; Wilhelm, Klaus; Curdt, Werner +5 more

Decay of the GRB 990123 Optical Afterglow: Implications for the Fireball Model

Hjorth, Jens; Walter, Fabian; Hippelein, Hans +49 more

A Search for Companions to Nearby Brown Dwarfs: The Binary DENIS-P J1228.2-1547

Brandner, W.; Basri, G.; Martin, E. L.