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All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Martian cratering. II - Asteroid impact history.

This paper considers the extent to which Martian craters can be explained by considering asteroidal impact. Sections I, II, and III of this paper derive the diameter distribution of hypothetical asteroidal craters on Mars from recent Palomar-Leiden asteroid statistics and show that the observed Martian craters correspond to a bombardment by roughly 100 times the present number of Mars-crossing asteroids. Section IV discusses the early bombardment history of Mars, based on the capture theory of Opik and probable orbital parameters of early planetesimals. These results show that the visible craters and surface of Mars should not be identified with the initial, accreted surface. A backward extrapolation of the impact rates based on surviving Mars-crossing asteroids can account for the majority of Mars craters over an interval of several aeons, indicating that we see back in time no further than part-way into a period of intense bombardment. An early period of erosion and deposition is thus suggested. Section V presents a comparison with results and terminology of other authors.

Hartmann, W. K.↗
NASA NTRS1972

High-energy radiations from space.

Survey of past, current, and planned U.S. high-energy astronomy observation (HEAO) experiments in space, and review of their significance. It is shown that astronomical observations from spacecraft during the first decade of space flight, though they be few and modest, have provided a wealth of new results that are most exciting, and that suggest that the next 20 or 30 years of space exploration may write a new chapter in the history of astrophysics and astronomy as important as the chapters initiated by Galileo or by the five-meter telescope on Mount Palomar. Special attention is given to the planned HEAO-A and HEAO-B experiment series.

Stuhlinger, E.↗
NASA NTRS1973

Kinematics of the Huyghenian region of the Orion Nebula.

Palomar data published by Wilson et al. (1959) on Orion Nebula wavelength 3726 and 5007 forbidden OII and OIII emission lines have been used to construct a presented pair of contour maps of isovelocities in intervals of 2.5 km/sec. The space motions of theta-1 and theta-2 Ori stars and nebula measurements are discussed.

Fischel, D.↗
NASA NTRS1973

Digital hardware and computer system for a digital image recorder.

Description of the digital memory and related computer system used at the Palomar Mountain Observatory. The memory was designed to have a large number of pixels, a high capacity for each pixel, and fast access for use with a variety of image sensors. As an image integration and storage device, this memory is shown to possess ideal properties, namely, it is strictly linear, has a wide dynamic range, and the image does not deteriorate with time. The observer has a visual display which enables him to monitor the image as it is being integrated.-

Dennison, E. W.↗
NASA NTRS1974

Astrometric observations of Saturn's satellites from McDonald Observatory, 1972

Observations of Saturn's satellites were reduced by means of secondary reference stars obtained by reduction of Palomar Sky Survey (PSS) plates. This involved the use of 39 SAO stars and plate overlap technique to determine the coordinates of 59 fainter stars in the satellite field. Fourteen plate constants were determined for each of the two PSS plates. Comparison of two plate measurement and reduction techniques on the satellite measurements demonstrate the existence of a serious background gradient effect and the utility of microdensitometry to eliminate this error source in positional determinations of close satellites.

Abbot, R. I.↗
NASA NTRS1974

The gamma Cygni supernova remnant and nebula

The object is anomalous, and the existing data appear to be rather contradictory or ambiguous. We discuss previous and new observations. The new observations are: Palomar Schmidt plates in the blue, yellow, red, and near-infrared; radiofrequency-continuum maps at 7.875 and 15.5 GHz; flux densities at 31.4 and 85 GHz; and H 94 alpha-line data. A nebula, found only in the red, is identifiable with a small component of a supernova remnant which is altogether about 1 deg in diameter. The spectral index of the large, nonthermal remnant is prevalently about -0.8, but the index is probably not less than -0.5 in the small component. The amorphous structure of the red nebula suggests that its light is nonthermal, since it is not a reflection nebula of the star gamma Cygni.

Johnson, H. M.↗
NASA NTRS1975

Astrometric observations of Saturn's satellites from McDonald Observatory, 1972

Observations of Saturn's satellites have been reduced by means of secondary reference stars obtained by reduction of Palomar Sky Survey plates. This involved the use of 29 SAO stars and plate overlap technique to determine the coordinates of 59 fainter stars in the satellite field. Fourteen plate constants were determined for each of the two PSS plates. Comparison of two plate measurement and reduction techniques on the satellite measures appears to demonstrate the existence of a serious background gradient effect and the utility of microdensitometry to eliminate this error source in positional determinations of close satellites.

Abbot, R. I.↗
NASA NTRS1975

Minor planets and comets in libration about the 2:1 resonance with Jupiter

We examine the orbits of minor planets in a search for objects librating about the 2:1 mean-motion resonance with Jupiter. Some 30 candidates are found among the Palomar-Leiden Survey and other unnumbered minor planets. Although almost all the orbits are very uncertain, there does seem to be an indication that librators of low orbital eccentricity do exist, contrary to the hypothesis by Giffen. We also tabulate data describing 12 comets that are temporarily librating about the 2:1 resonance. Finally, we present a discussion of what are apparently 'apocentric' librations. This type of libration, of which we find seven representatives among the numbered minor planets, can occur only for sufficiently small eccentricity. For such bodies, the role of Jupiter's eccentricity is vital; it is associated with a continuing alternation between apocentric libration and an oscillation of the line of apsides.

Franklin, F. A.↗
NASA NTRS1976

Optical identification of A0620-00

Identification of the optical counterpart to the transient X-ray source A0620-00 was made using image tube photography. Spectra taken subsequent to the identification showed no stellar absorption or emission features. Photometric data gave a V magnitude of 11.2 + or - .1. This is about 8 magnitudes brighter than the object appears on the Palomar Sky Survey.

Wolfson, R.↗
NASA NTRS1976

Optical counterparts of AFCRL infrared sources

The paper presents results of a search for optical counterparts of confirmed AFCRL infrared sources using the Palomar Sky Survey and direct photography with the Carnegie image tube camera. Positions and identification charts for possible counterparts to 26 AFCRL sources are presented. A list of AFCRL sources for which no optical counterparts were found is given, and some arguments to explain why the results of this search were negative are presented.

Lebofsky, M. J.↗
NASA NTRS1976

Emission object in Orion

The note draws attention to a structural feature in the Orion nebula, consisting of a parachute-shaped object converging on 64 Orionis, noted on H alpha photographs of the Orion nebula taken with the 76-cm Allegheny refractor. The same feature shows up clearly on a photograph taken in 1909 with the Mount Wilson 152-cm reflector, and on a photograph taken with the Palomar 5-m reflector. Measurements made on these three plates indicate a possible expansion of the object of about 3.6 seconds of arc per century, corresponding to a tangential velocity of about 90 to 100 km/sec. If the expansion continued at a linear rate, an explosive event may have occurred approximately 900 years ago.

Feibelman, W. A.↗
NASA NTRS1977

Retrieval techniques and graphics displays using a computerized stellar data base

The paper describes a stellar data retrieval system for which the data base consists of 28 machine-readable astronomical catalogs. Eleven of these catalogs have been combined into the Goddard Cross Index (GCI), which serves as the computer entry point to these catalogs. The full data entry from any of the GCI catalogs can be retrieved in a single computer run. With this system, it is possible to prepare candidates for observation by searching the data base for stars with given characteristics. Generation of plots of all catalog stars in or near the telescope's field of view to scale of Palomar, other atlases, or to the telescope itself for use as observing charts or to aid in identifying unknown sources, can be accomplished.

Mead, J.↗
NASA NTRS1977

Extragalactic sources with strong millimeter-wave emission

Observations at 90 GHz of a sample of 38 sources chosen to have flat or rising spectra between 0.318 and 5 GHz are reported. Roughly 25% of the sources were found to have flat or rising spectra between 5 and 90 GHz. The optical magnitude of each of the sources from the E print of the Palomar Sky Survey has also been estimated. Evidence is found for a correlation between the 90-GHz flux density and the optical magnitude, suggesting a relationship between the emission processes at these frequencies. Little evidence is found for a correlation between the low- and high-frequency spectral indices of the sources. This suggests that the sources tend to be opaque at centimeter wavelengths and optically thin at millimeter wavelengths. The properties of two of the more interesting sources are also discussed. Evidence is presented that strong millimeter activity may be generally associated with the BL Lac phenomenon.

Owen, F. N.↗
NASA NTRS1978

The spectrum of the halo surrounding the quasar PHL 1070

The quasar PHL 1070 and its surrounding halo of light have been observed with the Palomar multichannel spectrophotometer using circular and annular apertures. The central quasar has a magnitude of 16.6 and an emission-line redshift of 0.076 + or - 0.002. The halo light has a magnitude of 19.0 and a possible absorption-line system with an absorption redshift of 0.067 + or - 0.008. The magnitude, possible absorption lines, and probable spectral energy distribution of the halo are consistent with those of a normal galaxy at the redshift of the quasar.

Morton, D. C.↗
NASA NTRS1978

Evidence for a supermassive object in the nucleus of the galaxy M87 from SIT and CCD area photometry

Results are presented for broadband three-color (BVR) photometric observations of the peculiar elliptical radio galaxy M87, which were obtained with digital two-dimensional SIT and CCD detector systems on the Palomar 60-in. and 200-in. telescopes. The observations and the reduction procedures for the digital data are outlined, the luminosity profile of M87 is given, and a nuclear luminosity spike is found to be centered within 0.02 arcsec of the center of M87. Attempts are made to fit various theoretical models to the luminosity profile, and a satisfactory fit is obtained between the observed profile and a model involving a massive black hole in the galactic nucleus. A model-independent dynamical analysis of the central regions is performed which indicates that the nucleus of M87 contains a supermassive object of about 5 billion solar masses with a radius of no more than 100 pc and an M/L ratio of at least 60. The possible nature of this object is considered, and it is concluded that M87 is probably the most plausible candidate for a massive black hole in a galactic nucleus.

Young, P. J.↗
NASA NTRS1977

High-precision infrared sky survey at wavelength 2.7 microns

Preliminary results of an infrared survey of the equatorial sky zone (declinations 10 S to 10 N) with U.S. Air Force satellite sensors show that positions of previously unknown infrared sources are measured with an rms accuracy of 4 arc seconds, which is six times better than the best previous infrared survey. The search area per source for further study is thus 36 times smaller, so that identification of the infrared sources with optical objects in catalogs and sky photographs is facilitated, as is reacquisition of the sources with ground-based infrared telescopes. The survey extends the content of near-infrared source catalogs to lower flux densities and adds information at a wavelength not observable from the ground. Objects found in the survey include cool giants and supergiants, long-period and semi-regular variable stars, and sources identified with faint red stars visible on the Palomar Observatory Sky Survey.

Sweeney, L. H.↗
NASA NTRS1978

Molecular clouds in the vicinity of W3, W4, and W5

An extensive and well-sampled map of CO emission over the entire complex consisting of the H II regions W3 (IC 1795), W4 (IC 1805), and W5 (IC 1848) is presented which was obtained at an angular resolution of 8 arcmin. A contour map of integrated (C-12)O emission overlaid on the corresponding fields of the Palomar Sky Survey is provided along with a map of the peak (C-12)O brightness temperature for the W3-W4 region. Two large cloud complexes are found within the area surveyed, and three bright CO condensations are resolved in the peak-temperature map. Column densities and masses are estimated for the cloud complex in the W3-W4 region, and it is suggested that the ionization front of W4 and the molecular cloud are interacting physically. Two condensations associated, respectively, with W3 and W3 (OH) are shown to contain unmistakable evidence for recent OB star formation.

Lada, C. J.↗
NASA NTRS1979

The discovery and orbit of /2060/ Chiron

'Slow-moving Object Kowal' was discovered as an asteroidal object of photographic magnitude about 18 on photographic plates made on October 18 and 19, 1977 with the 122-cm Schmidt telescope at Palomar Observatory. It was determined that the object was located between 14 and 17 AU from the earth in a low-inclination, near-circular orbit. Examination of subsequent plates and earlier observations of the area allowed a more exact calculation of the orbital elements, which suggest the object to be in 3:5 resonance with Saturn at a perihelion of 8.5 AU. The object's orbital behavior suggests that of an inactive comet perturbed by Saturn from a previous orbit, however its magnitude is uncharacteristically large for a comet. It is proposed that object Kowal was once an ordinary minor planet that was deflected into its present orbit by collisions with other minor planets and a series of encounters with Jupiter and Saturn. The object has received the minor planet number (2060) and the name of Chiron has been proposed.

Kowal, C. T.↗