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Smith, H. A.

Publications and source records attributed to Smith, H. A..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Intensity and extinction irregularities in the H2 emission from Orion

Fourteen lines of the v = 1-0 and v = 2-1 2 micron H2 quadrupole spectrum were measured in a series of ground-based spectroscopic observations of four locations within the Orion molecular cloud-H2 emission complex. Beam sizes of 7 and 10 arcsec were used, with a resolution of 1.8/cm. The results indicate that there are differences in the extinction between regions of as much as 20 mag. In particular there appears to be a ridge of material near the object IRS 2 (= IRc 9), a previously suggested source of activity. The 2-1 S (3) line intensity is substantially stronger at Peak 2 than the present models predict, and this observation is the first indication that there may be a non-Boltzmann distribution within the vibrational levels of shock-excited H2. A detection of the 1-0 Q (6) line is also reported, a feature which was previously absent in spectra of the Orion cloud.

Smith, H. A.↗
NASA NTRS1982

Airborne observations of the Orion molecular hydrogen emission spectrum

The Orion near-infrared H2 emission spectrum was observed from an altitude of 12.5 km in order to measure line intensities free from interference by terrestrial H2O. For the peak source, the observations indicate that the differential extinction between 4126 and 4712 per cm is 0.59 + or -0.06 mag, and the relative line intensities are consistent with those expected from a homogeneous source in approximate LTE at 1540 + or -100 K. An anomalous ortho/para H2 abundance ratio of 3.5(+ or - 0.2):1 is found, and the estimated total luminosity in vibrationally excited H2 lines is 300 + or - 100 solar luminosities. Rough molecular abundance limits, based on the missing H2 Q(6) line and the good agreement between other line intensities and the LTE model, place the H2 region no deeper within OMC-1 than the IR cluster and no shallower than 50 percent of the depth to the cluster.

Davis, D. S.↗
NASA NTRS1982

Infrared spectra of galactic center sources

Absorption due to CO and emission from atomic hydrogen and neutral helium observed in high resolution 2-micron spectra of five compact sources in the central parsec of the galaxy furnish information concerning the condition, distribution and kinematics of red giant stars and ionized gas in the galactic core. It is found that all three red giant sources observed are blueshifted, and that there are no detectable absorptions in the continuum of the central source IRS 16.

Wollman, E. R.↗
NASA NTRS1982

Far-infrared observations of FU Orionis

The peculiar star FU Orionis is located in the southeast extension of Barnard 35 (B35), a bright-rimmed molecular cloud, and in the more extended, low-density region around Lambda Orionis. In connection with the present investigation, far-infrared observations of the star were undertaken in order to obtain a better estimate of the total luminosity of FU Ori and to better understand its relationship with the B35 cloud. FU Orionis was observed on 1981 January 23 with the 90 cm telescope on board the NASA Kuiper Airborne Observatory. The far-infrared results suggest that much of the radiation from the stellar source does not interact with either the 225 K circumstellar dust or the exterior 15 K material. The total luminosity of FU Ori is now seen to be about the same as the visible luminosity, and at the distance to B35 ridge dilution would make any isotropic effects negligible.

Smith, H. A.↗
NASA NTRS1982

High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion Molecular Cloud

The pure rotational S(2) line of H2 at 12.28 microns was sought in 44 positions in the Orion Molecular Cloud with 6-arcsec beams and 35 km/s spectral resolution; and it was detected in 27 positions. The lines are approximately symmetric and have full widths at half-maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that observed in the 2-micron hydrogen transitions; however, unexpectedly complex line profiles and point-to-point variations in line shapes appear, particularly in the region near IRc9.

Beck, S. C.↗
NASA NTRS1981

Far-infrared and submillimeter observations of Barnard 35 - Heat sources for bright-rimmed molecular clouds

Far-infrared and submillimeter continuum observations of a region of enhanced gas temperature in Barnard 35 are presented which were obtained in a study of dust and gas energetics in the bright-rimmed molecular cloud. Observations were obtained with the 90-cm telescope on board the NASA Kuiper Airborne Observatory, together with ground-based observations of the CO lines. The spectrum is found to correspond to a dust temperature of 10 + or - 5 K. A total dust luminosity of about 69 solar luminosities is estimated for the cloud, which may easily be supplied by stellar radiation from the background field or the Lambda Ori cluster. Observations of CO emission at 2.7 mm indicate a gas temperature of 23.4 + or - 3.5 K. The difference between the gas and dust temperatures confirms earlier suggestions that the gas and dust are not in thermal equilibrium and that gas-dust collisions are not the heat source for the molecular gas, however the actual source of the molecular gas heating remains uncertain.

Lada, C. J.↗
NASA NTRS1981

Infrared atomic hydrogen line formation in luminous stars

Infrared atomic hydrogen lines observed in luminous stars, generally attributed to compact circumstellar H II regions, can also be formed in the winds likely to emanate from these stars. Implications are discussed for the class of obscured infrared point sources showing these lines, and an illustrative model is derived for the BN object in Orion. Such stellar winds should also produce weak, but detectable, radio emission.

Krolik, J. H.↗
NASA NTRS1981

A study of ethane on Saturn in the 3 micron region

C2H6 has been detected in absorption on Saturn from 3-micron airborne spectra. Based on comparisons with laboratory spectra of C2H6, the ethane abundance has been estimated at 7.5 plus or minus 3.5 cm-amagat, equivalent to a column abundance of 3.0 plus or minus 1.4 cm-amagat. The results support expectations that CH4 photolysis is a major disequilibrating mechanism in the upper atmosphere of the outer planets and Titan.

Bjoraker, G. L.↗
NASA NTRS1981

Molecular hydrogen and the 2 micron spectrum of NGC 7027

The spectrum of the planetary nebula NGC 7027 in the range 1.6-2.5 microns was obtained with a resolution of 1.2 per cm. The presence of molecular hydrogen emission in the v = 1-0 S(1), Q(1), and Q(3) lines is confirmed, and the detection of H2 lines v = 1-0 Q(2), Q(4), S(0), and S(2) is reported. The H2 line strengths, with upper limits for the v = 2-1 band, suggest a model in which the emitting gas is confined to clumps heated by a shock front accompanying an expanding H II region. Emission lines are also detected from atomic hydrogen (Pfund and Brackett series) and from He I and He II.

Smith, H. A.↗
NASA NTRS1981

High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion molecular cloud

The pure rotational S(2) line of molecular hydrogen at 12.28 microns was looked for in 44 positions in the Orion moleular cloud with 6 in. beams and 35 km/s spectral resolution; it was detected in 27 positions. Emission was observed over a velocity range of + or - 100 km/s. The lines are approximately symmetric, and have full widths at half maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that seen in the 2 micron hydrogen transitions. However, unexpectedly complex line profiles and point-to-point variations in linear shapes appear, particularly in the region near IRc9.

Beck, S. C.↗
NASA NTRS1980

The middle-infrared spectrum of Saturn - Evidence for phosphine and upper limits to other trace atmospheric constituents

Observations of Saturn at high spectral resolution in the middle-IR spectral region (2.5-5.6 microns) were obtained using a Fourier spectrometer at ground-based and airborne observatories. These spectra establish that PH3 exists on Saturn with an abundance at least equal to the solar P/H value, and probably enhanced by about a factor of 2. No evidence is found for gaseous or solid NH3 on Saturn throughout this spectral region, and upper limits to several other molecules (H2O, HCN, SiH4, and GeH4) are determined. Frequent comparisons of the spectral data for Saturn with observations and interpretations of IR studies of Jupiter show that these two planetary atmospheres are chemically similar, with major observational differences accounted for by reduced H2O and NH3 abundances in Saturn's colder atmosphere.

Larson, H. P.↗
NASA NTRS1980

Spectroscopic evidence for two achondrite parent bodies - Asteroids 349 Dembowska and 4 Vesta

A Fourier spectrometer was used to obtain IR spectra of asteroids 349 Dembowska and 4 Vesta. The spectrum of Dembowska shows olivine and pyroxene with an olivine/pyroxene abundance ratio greater than 2, and possibly as high as 10. This is probably an unsampled achondritic composition, similar to the unique achondrite ALHA 77005. Dembowska's mineralogy therefore appears related to the achondrites; pyroxene and plagioclase feldspar are seen, with a pyroxene/feldspar abundance ratio between 1.5 and 2.0. Time-resolved observations over one-half of the rotation period indicate compositional homogeneity; both 349 Dembowska and 4 Vesta can be considered as candidates for the parent bodies of igneous meteorites.

Feierberg, M. A.↗
NASA NTRS1979

The spectrum of the Becklin-Neugebauer source in Orion from 3.3 to 5.5 microns

Spectra of the Becklin-Neugebauer source in Orion and the associated nebula are presented covering the complete range from 3.3-5.5 microns with a resolution of 1.2 kaysers. The data were taken in December 1976 and February 1978. Atomic hydrogen emission lines of Brackett-alpha and Pfund-beta are seen, as well as molecular CO absorptions. No other features intrinsic to BN were detected. The December 1976 data show an anomalously high intensity for Pfund-beta line. Theoretical considerations are presented which suggest that Pfund-beta radiation arises in a small dense region, with the transition possibly lasing.

Smith, H. A.↗
NASA NTRS1979

Remote spectroscopic identification of carbonaceous chondrite mineralogies Applications to Ceres and Pallas

High-resolution spectroscopic observations of asteroids Ceres and Pallas have been obtained in the 1.0- to 2.6-micron region. Combined with previous spectral measurements at other wavelengths, this work presents the broadband spectral reflectances of these asteroids over the 0.4- to 3.6-micron region. This extended coverage permits new analyses of the surface mineralogies of these objects. Using laboratory comparison spectra of meteorites and mixtures of terrestrial minerals, the surfaces of Ceres and Pallas are consistent with mixtures of opaques and hydrated silicates, such as are found in types C1 and C2 meteorites. This research emphasizes the importance of the 3-micron spectral region for studying by remote methods the relationship of carbonaceous chondrite mineralogies to asteroid surfaces.

Larson, H. P.↗
NASA NTRS1970

Emergency space-suit helmet

A frusto-conically shaped distensible component is described which inflates to encircle a portion of the wearer's head and carries a collapsible member which automatically extends over the remaining portion of the head. A pulley arrangement secured between the walls of the distensible component automatically extends and retracts the collapsible member. When deflated, the unit is carried on the back of the wearer so as to provide an automatic emergency space suit helmet.

Smith, H. A.↗