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Weissman, P. R.

Publications and source records attributed to Weissman, P. R..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Stellar Encounters with the Oort Cloud Based on Hipparcos Data

We have combined Hipparcos proper motion and parallax data for nearby stars with ground-based radial velocity measurements to find stars which may have passed (or will pass) close enough to the Sun to perturb the Oort cloud.

comets solar system stars kinematics solar neighbo↗
NASA NTRS1997

Are the Leonid Meteor Storms Coming?

In February 1997, the Japanese Space Agency ISAS launched the first space VLBI Space Observatory Program Satellite (VSOP) using the newly developed M-V launch vehicle.

Leonid Meteor Storms↗
NASA NTRS1997

A search for stars passing close to the sun

Hipparcos proper motion and parallax data are combined for nearby stars with ground-based radial velocity measurements in order to identify stars which may have passed, or will pass, close enough to the sun to perturb the Oort cloud. Close stellar encounters could deflect large numbers of comets into the inner solar system, with possible serious consequences for impact hazards on the earth. Only one star, Gliese 710 is found with a predicted closest approach of less than 0.5 pc, although several stars come within 1 pc during a 8.5 M year interval. In most cases, the uncertainty in closest approach distance is dominated by uncertainties in the barycenter motion of binary systems. A program to obtain new radial velocities for stars in the sample with no previously published values is underway.

Garcia-Sanchez, J.↗
NASA NTRS1997

Temperature, Size and Energy of the Shoemaker-Levy 9 G-Impact Fireball

The fortunate position of the Galileo spacecraft provided us with a unique opportunity to directly observe the Shoemaker-Levy 9 impacts as they occurred on the far side of Jupiter, and we present observations of the G fireball obtained by the Near Infrared Mapping Spectrometer (NIMS).

Comets↗
NASA NTRS1997

A Search For Stars Passing Close to The Sun

We have combined HIPPARCOS proper motion and parallax data for nearby stars with ground-based radial velocity measurements to find stars which may have passed close enough to the sun to perturb the Oort cloud.

Stars↗
NASA NTRS1997

Temperature, Size, and Energy of the Shoemaker-Levy 9 G-Impact Fireball

The fortunate position of the Galileo spacecraft provided us with a unique opportunity to directly observe the Shoemaker- Levy 9 impacts as they occurred on the far side of Jupiter, and we present observations of the G fireball obtained by the Near Infrared Mapping Spectrometer (NTMS). These measurements were performed using 10 spectral bands, 4 representing continua and spanning the wavelength range 1.84 to 4.38 mu. Fireball signals were evident for up to 80 sec, with the time of intensity maxima and duration being greater for longer wavelengths. Color temperatures and effective emitting areas were estimated by fitting blackbody functions at the four continuum wavelengths. Good blackbody fits were found, and their intensities at shorter wavelengths show excellent agreement with the Galileo Photopolarimeter/Radiometer measurements. Temperatures near the beginning are above 3000 K, decreasing to approximately 1000 K after 1 min. The corresponding areas range from 400 to 20,000 sq km. The effective diameter of the luminous fireball shows approximately linear time variation, at least for the first 45 sec. From the temperature-effective diameter relation we find an adiabatic coefficient of lambda = 1.2+/-0.1, much as expected from theoretical considerations. The luminosity, when integrated over the period of observations and assuming a Stephan-Boltzmann radiator, gives an above-cloud radiative energy loss of 0.48+/- 0.13 x 10(exp 25) erg.

Carlson, R. W.↗
NASA NTRS1995

Are the Leonid Meteor Storms Coming?

On Nov. 17, 1996 an extraordinary Leonid meteor storm (144,000 per hour) was witnessed by observers in central and western United States. With an orbital period of 33 years, the next return to perihelion will be Feb. 28, 1998. Because the distribution of the particles flying in formation with the parent comet is poorly known, no secure predictions can be made for Leonid meteor storms in the coming years.

Comets Astronomy Leonid Meteor Storms Leo↗