Search NASA⌕ Search

SEARCH · Search NASA

Results for “Periodic orbits”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

The orbital period of 4U/MXB 1636-53 (V801 Arae)

The results of CCD photometry of the optical counterpart (V801 Arae) of the X-ray burst source 4U/MXB 1636-53, obtained between 1984 and 1988 are reported. From these data, and additional measurements discussed previously, a linear orbital ephemeris P(orb) = 3.803878 + or - 0.000022 h covering the interval between 1980 and 1988 is derived. The results confirm that substantial night-to-night variations occur in the shape of the light curve, superposed on the periodic brightness variations. No evidence is found for a relation between orbital phase and the delays of optical bursts relative to the coincident X-ray bursts. The variation with orbital phase of the corresponding ratios of optical to X-ray burst fluences and peak fluxes does not follow the average optical light curve. These results suggest that substantial long-term changes occur in the spatial distribution of reprocessing matter in the binary system.

Van Paradijs, J.↗
NASA NTRS1987

Do slow orbital periodicities appear in the record of earth's magnetic reversals?

Time-series spectral analysis has been performed on the dates of geomagnetic reversals of the last 20 Myr BP and earlier. Possible evidence is found from the presence of high spectral peaks for two very long periodicities, 0.4 Myr and 1.3 Myr, that may be associated with slow variations of the earth's orbital eccentricity as predicted by Berger. However, statistical significance tests and a number of other arguments do not confirm the two detections.

Stothers, Richard B.↗
NASA NTRS1993

Effect of parking orbit period on aerocapture for manned Mars missions

Aerocapture has previously been identified as a critical technology for manned Mars missions. A wide range of parking orbits is available into which an aerobraking vehicle could be captured, and earlier authors have advocated different target orbits for various reasons. The choice of the parking orbit impacts the amount of energy which must be dissipated during the atmospheric trajectory. The effect of this choice on the entry corridor width, the required vehicle L/D, and the aerothermal environment are explored in this paper.

Lyne, James E.↗
NASA NTRS1980

Variations in the Nimbus-7 scanning multichannel microwave radiometer cold reference antenna signals and temperatures during two orbital periods

The observed effects of solar radiance on the Nimbus 7 scanning multichannel microwave radiometer (SMMR) cold reference signal are discussed. Unexpected diurnal responses in this signal sometimes larger than the typical cold reference signal resulted from acquisition of the solar disc. Solar heating of the SMMR components as a function of orbital locations was correlated with the cold reference radiances for two sets of sequential orbit six months apart.

Gloersen, P.↗
NASA NTRS1994

Is the changing orbital period of EXO 0748-676 evidence for a triple system?

We present eclipse timing measurements of the low-mass X-ray binary (LMxB) EXO 0748-676 made with ASCA. These measurements, when combined with previous results, are consistent with the hypothesis that eclipse times are modulated by a third body. The parameters of the orbit of the postulated third body are now apparently well constrained and will allow further observations to effectively test the hypothesis that EXO 0748-676 is a triple system. The derived orbital parameters are such that, unless the inclination angle is very low, a third body in the system must have a mass less than the lower limit for a main-sequence star.

Corbet, R. H. D.↗
NASA NTRS1979

The orbital period of Algol - 1964 to 1978

A photoelectric observation of minimum light for Algol is reported: JD 2443565.5785 (visual) and JD 2443565.5802 (blue). The times of minima obtained between 1964 and 1978 indicate that a period decrease may have occurred about 1975. It is suggested that this period change, as well as the radio and X-ray activity and spectroscopic anomalies observed during 1975, may have been due to a mass-transfer event that occurred around that time.

Mallama, A. D.↗
NASA NTRS1992

Off-center nuclei in galaxies

The nucleus of a galaxy orbits around the mass centroid. Orbital motions appear overstable in numerical experiments started with a galaxy's nucleus at rest atop its mass centroid. The amplitude doubles in 6-10 orbital periods. Orbits precess, nutate, and change their amplitudes, but they keep fairly constant periods. Orbital periods are in resonance with local particle motions, and amplitudes reach a core radius. This resonance suggests that center motions are a local, rather than a global, phenomenon. The overstability implies that a galaxy cannot be formed in nature with its nucleus at rest atop its mass centroid, and that nuclei orbit the mass centroid in real galaxies. These center motions should show up observationally as a shift of the nucleus away from the center defined by nearby isophotes. Off-center nuclei have been reported in many galaxies (e.g., M33, M101, NGC 3379, NGC 3384). Other kinds of observations confirmed the picture of nonsteady galactic centers as well. Gas trapped in moving nuclear regions of a galaxy should show strange flow patterns with possible shocks. The nuclear regions of galaxies including Milky Way and of globular clusters are not likely to be in a static steady state.

Miller, R. H.↗