Search NASA⌕ Search

SEARCH · Search NASA

Results for “millimeter astronomy”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Multi-spectral Observations of the Star Formation: the Role of Far Infrared Photometry

The study and analysis of complex astrophysical process requires a multispectral approach employing many of the tools of modern astronomy. The study of the interaction of early type stars with the interstellar medium is an example of this point. Two examples of multi-spectral studies of individual objects are reviewed. The predominent theme is the combination of high resolution far infrared photometry, radio images and millimeter-wave spectroscopy with the radio sensitive to the ionization, the millimeter-wave lines showing the structure and excitation of the gas and the far infrared providing a picture of the energetics of the dust which connects the star to the interstellar medium. Multispectral observations of FIRSSE and IRAS objects are discussed.

Schwartz, P. R.↗
NASA NTRS1995

Thermal Balance in Dense Molecular Clouds: Radiative Cooling Rates and Emission-Line Luminosities

We consider the radiative cooling of fully shielded molecular astrophysical gas over a wide range of temperatures ( 10 K < T < 2500 K) and H2 densities ( 10(exp 3)/cc < n(H2) < 10(exp 10)/cc). Our model for the radiative cooling of molecular gas includes a detailed treatment of the interstellar chemistry that determines the abundances of important coolant molecules, and a detailed treatment of the excitation of the species H2, CO, H2O, HCl, O2, C, O, and their isotopic variants where important. We present results for the total radiative cooling rate and for the cooling rate due to individual coolant species, as a function of the gas temperature, density, and optical depth. We have also computed the individual millimeter, submillimeter, and far-infrared line strengths that contribute to the total radiative cooling rate, and we have obtained example spectra for the submillimeter emission expected from molecular cloud cores. Many of the important cooling lines will be detectable using the Infrared Space Observatory and the Submillimeter Wave Astronomy Satellite.

Neufeld, David A.↗
NASA NTRS2022

Phosphine in the Venusian Atmosphere: A Strict Upper Limit from SOFIA GREAT Observations

The presence of phosphine (PH3) in the atmosphere of Venus was reported by Greaves et al. based on observations of the J = 1–0 transition at 267 GHz using ground-based, millimeter-wave spectroscopy. This unexpected discovery presents a challenge for our understanding of Venus's atmosphere, and has led to a reappraisal of the possible sources and sinks of atmospheric phosphorous-bearing gases. Here we present results from a search for PH3 on Venus using the German REceiver for Astronomy at Terahertz Frequencies instrument aboard the Stratospheric Observatory for Infrared Astronomy aircraft, over three flights conducted in November 2021. Multiple PH3 transitions were targeted at frequencies centered on 533 and 1,067 GHz, but no evidence for atmospheric PH3 was detected. Through radiative transfer modeling, we derived a disk-averaged upper limit on the PH3 abundance of 0.8 ppb in the altitude range 75–110 km, which is more stringent than previous ground-based studies.

M. A. Cordiner↗
NASA NTRS2000

Bolometric Array Detectors for Space-Borne Astronomy

Funding from the NASA Innovative Research Grant was used to develop bolometric detectors. As described in the proposal, silicon nitride micromesh ('spider-web') absorbers had been demonstrated at U.C. Berkeley but not developed to be flight-worthy devices. We proceeded to first fabricate bolometers with Neutron Transmutation Doped (NTD) Ge thermistors that demonstrated high optical coupling (Church et al. 1996) and were developed for a ground-based millimeter-wave receiver (Mauskopf et al. 1997). The next generation of devices used In bump-bonded thermistors to achieve devices with performance product NEP*sqrt(tau) = 3e - 18 j at 300 mK, demonstrating a full order of magnitude improvement over pervious devices. These devices achieved an NEP = 1e-18 W/rtHz (Murray et al. 1996) as promised in the proposal. Sensitivities as good as 1e - 19 W/rtHz appear achievable with the silicon nitride architecture (Bock et al. 1997). Finally, arrays of micromesh bolometers were shown to be feasible in the last year of the program by etching a large number of devices on a single silicon wafer (75 mm). Full arrays were subsequently demonstrated for selection on the ESA/NASA Far-Infrared Space Telescope (FIRST) in competition with detectors provided by CEA in France and GSFC in the US Micromesh bolometer arrays are now baselined for both the ESA/NASA Planck and FIRST missions.

Lange, Andrew E.↗
NASA NTRS1990

Emission from small dust particles in diffuse and molecular cloud medium

Infrared Astronomy Satellite (IRAS) observations of the whole galaxy has shown that long wavelength emission (100 and 60 micron bands) can be explained by thermal emission from big grains (approx 0.1 micron) radiating at their equilibrium temperature when heated by the InterStellar Radiation Field (ISRF). This conclusion has been confirmed by continuum sub-millimeter observations of the galactic plane made by the EMILIE experiment at 870 microns (Pajot et al. 1986). Nevertheless, shorter wavelength observations like 12 and 25 micron IRAS bands, show an emission from the galactic plane in excess with the long wavelength measurements which can only be explained by a much hotter particles population. Because dust at equilibrium cannot easily reach high temperatures required to explain this excess, this component is thought to be composed of very small dust grains or big molecules encompassing thermal fluctuations. Researchers present here a numerical model that computes emission, from Near Infrared Radiation (NIR) to Sub-mm wavelengths, from a non-homogeneous spherical cloud heated by the ISRF. This model fully takes into account the heating of dust by multi-photon processes and back-heating of dust in the Visual/Infrared Radiation (VIS-IR) so that it is likely to describe correctly emission from molecular clouds up to large A sub v and emission from dust experiencing temperature fluctuations. The dust is a three component mixture of polycyclic aromatic hydrocarbons, very small grains, and classical big grains with independent size distributions (cut-off and power law index) and abundances.

Bernard, J. P.↗
NASA NTRS2006

A Brief Summary of Some of the Laboratory Astrophysics Workshop

Our present knowledge of the molecular universe has come primarily from radio observations [ I include here millimeter and submillimeter in this rubric]. There are a number of reasons for this but the primary one is the extremely high spectral resolution. The ease of observing emission from the volume of dense molecular clouds without significant attenuation by scattering from dust has shown this to be the powerful observational tool for molecular astronomy. Finally the relative simplicity of rotational compared to vibrational or electronic spectroscopy allows carrier identification as well as facile evaluation of cloud conditions such as density and temperature. These virtues become tenuous as the astronomical observations are pushed to higher frequencies for enhanced observational sensitivity. Thus precision rest frequencies are mandatory for the search for new species. We may inquire about which new species require particular attention, and which species may be relatively safely predicted on the basis of lower frequency laboratory measurements. For a rigid rotor the three rotational constants are sufficient to completely specify the transition frequencies. The intensities require the three components of the electric dipole moment. For semirigid species, where the centrifugal distortion, may be treated at the quartic level of angular momentum (Bunker et al. 1998), up to five additional constants are required (Watson 1967). There are a number of such species of considerable interest, where laboratory measurements are adequate for astronomical searches.

Klemperer, William↗
NASA NTRS1981

Infrared Astronomy

Several observational programs in infrared astronomy are described and significant findings are briefly discussed. The near infrared work concentrates largely on the use of the 5 m Hale telescope in spectroscopic and photometric studies of extragalactic sources. Observations of the P alpha line profile in a low redshift quasar, X-ray bursters, reflection nebula, and cataclysmic variables are included. Millimeter continuum observations of dust emission from quasars and galactic molecular clouds are also discussed. Finally, improvements to instrumentation are reported.

Neugebauer, G.↗
NASA NTRS2017

The Stratospheric Observatory for Infrared Astronomy (SOFIA) - Current Status, Recent Results, Future Plans, and Synergies with the AKARI Archive

The Stratospheric Observatory for Infrared Astronomy comprises a 2.7m diameter telescope mounted in a heavily modified B747SP aircraft. The SOFIA program is a joint US NASA and German DLR program, with the development and operations costs split roughly 80%:20%, respectively. Although the observatory is funded by these two nations, its observing time is open to proposals from astronomers of any nationality. The observatory has been flying and taking scientific data since 2010 and currently observes astronomical targets from the stratosphere for approximately 800 research flight hours per year. Seven science instruments (with an eighth coming online in 2020) cover the visible to sub-millimeter wavelengths with a variety of spectral resolutions ranging up to 1e8. The AKARI Archive with its 1.7 to 180 micron wavelength coverage is a natural complementary source for follow-up observations with SOFIA. This presentation will cover the current SOFIA technical capabilities and will present a few recent science highlights that demonstrate the SOFIA/AKARI complementarity. The presentation will also cover the SOFIA proposal process and will summarize other partnership opportunities for additional observing time on SOFIA.

Astronomy↗
NASA NTRS2007

Indium Hybridization of Large Format TES Bolometer Arrays to Readout Multiplexers for Far-Infrared Astronomy

The advance of new detector technologies combined with enhanced fabrication methods has resulted in an increase in development of large format arrays. The next generation of scientific instruments will utilize detectors containing hundreds to thousands of elements providing a more efficient means to conduct large area sky surveys. Some notable detectors include a 32x32 x-ray microcalorimeter for Constellation-X, an infrared bolometer called SAFIRE to fly on the airborne observatory SOFIA, and the sub-millimeter bolometer SCUBA-2 to be deployed at the JCMT which will use more than 10,000 elements for two colors, each color using four 32x40 arrays. Of these detectors, SCUBA-2 is farthest along in development and uses indium hybridization to multiplexers for readout of the large number of elements, a technology that will be required to enable the next generation of large format arrays. Our current efforts in working toward large format arrays have produced GISMO, the Goddard IRAM Superconducting 2-Millimeter observer. GISMO is a far infrared instrument to be field tested later this year at the IRAM 30 meter telescope in Spain. GISMO utilizes transition edge sensor (TES) technology in an 8x16 filled array format that allows for typical fan-out wiring and wire-bonding to four 1x32 NIST multiplexers. GISMO'S electrical wiring is routed along the tops of 30 micron walls which also serve as the mechanical framework for the array. This architecture works well for the 128 element array, but is approaching the limit for routing the necessary wires along the surface while maintaining a high fill factor. Larger format arrays will benefit greatly from making electrical connections through the wafer to the backside, where they can be hybridized to a read-out substrate tailored to handling the wiring scheme. The next generation array we are developing is a 32x40 element array on a pitch of 1135 microns that conforms to the NIST multiplexer, already developed for the SCUBA-2 instrument This architecture will utilize electrical connections that route from the TES to the support frame and through the wafer. The detector chip will then be hybridized to the NIST multiplexer via indium bump bonding. In our development scheme we are using substrates that allow for diagnostic testing of electrical continuity across the entire array and we are testing our process to minimize or eliminate any contact resistance at metal interfaces. Our goal is hybridizing a fully functional 32x40 array of TES bolometers to a NIST multiplexer. The following work presents our current progress toward enabling this technology.

Miller, Timothy M.↗
NASA NTRS1984

Molecular astronomy at submillimeter wavelengths

It is pointed out that the region of the spectrum from 300 to 3000 GHz (100 to 1000 microns), which is referred to as the submillimeter, is one of the least explored areas in the electromagnetic spectrum. The reasons for this situation are related to a lack of adequate instrumentation for detecting the radiation and an almost complete absorption of the radiation by the earth's atmosphere. The vast majority of the rotational transitions of molecules occur in the millimeter and submillimeter wavelength region of the spectrum. The strength of the lines increases at higher frequencies until a condition is reached in which the energy levels are no longer populated. The study of molecular clouds at submillimeter wavelengths promises to provide new important results. Attention is given to the design of suitable submillimeter receivers, problems of atmospheric transmission, and galactic molecular lines.

Buhl, D.↗
NASA NTRS1999

Airborne Astronomy Program

Our understanding about the inter-relationship between the collapsing cloud envelope and the disk has been greatly altered. While the dominant star formation models invoke free fall collapse and r(sup -1.5) density profile, other star formation models are possible. These models invoke either different cloud starting conditions or the mediating effects of magnetic fields to alter the cloud geometry during collapse. To test these models, it is necessary to understand the envelope's physical structure. The discovery of disks, based on millimeter observations around young stellar objects, however makes a simple interpretation of the emission complicated. Depending on the wavelength, the disk or the envelope could dominate emission from a star. In addition, the discovery of planets around other stars has made understanding the disks in their own right quite important. Many star formation models predict disks should form naturally as the star is forming. In many cases, the information we derive about disk properties depends implicitly on the assumed envelope properties. How to understand the two components and their interaction with each other is a key problem of current star formation.

Butner, Harold M.↗
NASA NTRS2022

Alma Images the Eccentric HD 53143 Debris Disk

We present ALMA 1.3 mm observations of the HD 53143 debris disk—the first infrared or millimeter image produced of this ∼1 Gyr old solar analog. Previous HST STIS coronagraphic imaging did not detect flux along the minor axis of the disk, which could suggest a face-on geometry with two clumps of dust. These ALMA observations reveal a disk with a strikingly different structure. In order to fit models to the millimeter visibilities and constrain the uncertainties on the disk parameters, we adopt a Markov Chain Monte Carlo approach. This is the most eccentric debris disk observed to date with a forced eccentricity of 0.21 ± 0.02, nearly twice that of the Fomalhaut debris disk, and also displays an apocenter glow. Although this eccentric model fits the outer debris disk well, significant interior residuals remain, which may suggest a possible edge-on inner disk, which remains unresolved in these observations. Combined with the observed structure difference between HST and ALMA, these results suggest a potential previous scattering event or dynamical instability in this system. We also note that the stellar flux changes considerably over the course of our observations, suggesting flaring at millimeter wavelengths. Using simultaneous TESS observations, we determine the stellar rotation period to be 9.6 ± 0.1 days.

Radio astronomy↗
NASA NTRS1994

A reinterpretation of millimeter observations of nearby IRAS excess stars

We analyze new and previously published 1300, 870, and 800 micrometers, single-element bolometer observations of Vega (alpha Lyr), Formalhaut (alpha PsA), epsilon Eri, tau(sup1) Eri, and Beta Leo. We show that these data are consistent with models in which the dust disks around these stars are larger than the radio telescope beams with which they were observed; thus, these disks may be many hundreds of AU in radius or larger. Our interpretation of submillimeter/millimeter measurements of these stars also indicates that for some Infrared Astronomy Satellite (IRAS) IR excess stars the assumption that there is no astrophysical flux in the OFF beams, when using the standard ON-minus-OFF chopping technique and the chop distance is less than 1000AU, may be incorrect. Therefore, for IRAS IR excess stars within approximately 20 pc, virtually all submillimeter/millimeter chopping observations with chop throws less than 100" may have subtracted away some or most of the flux associated with their circumstellar disks. Finally, we present new 1300 micrometers continuum observations of Vega made with chop throws of 500 and 1000 AU. These data are consistent with an interpretation in which Vega has a disk that is at least 1000AU in radius; this disk could have a region with much less material per beam area near 500 AU than at both 100 AU and 1000 AU, corresponding to a gap at the orbital distance of alpha Lyr B. The observations of Vega are also consistent with the assumption that the circumVega dust structure is unresolved. Thus, these new data very effectively illustrate that the 'standard' model of small, unresolved, dust structures around main-sequence IRAS IR excess stars is not unique. Maps of IRAS IR excess stars, which soon will be available from submillimeter/millimeter array detectors, will determine whether the paradigm shift we propose will occur.

Weintraub, David A.↗
NASA NTRS1976

NASA's 91-cm. airborne telescope

The Gerard P. Kuiper Airborne Observatory (KAO), commissioned in May 1975, is the result of the multi-year NASA program of infrared observations from high-flying aircraft. The KAO is a highly modified Lockheed C-141 jet transport, equipped with a 91-cm bent-Cassegrain telescope, as an international facility for research in infrared astronomy. To minimize the effects of aircraft vibration, the telescope is mounted on four pneumatic shock absorbers, and the entire assembly is balanced on the side of a spherical compressed-air bearing, containing a 0.018 mm-thick air film under a pressure of 19 atmospheres. The use of the KAO is not limited to infrared research, its total observable wavelength band extending from the near UV (3000 A) to the millimeter region. Design and technical characteristics of the telescope are discussed, including the image stabilization and target acquisition systems, as well as observational results obtained during the first year of the KAO operation.

Cameron, R. M.↗
NASA NTRS2003

High Resolution Imaging of Circumstellar Disks at Millimeter Wavelengths

Our program uses the techniques of millimeter interferometry to make high resolution observations of dust continuum emission to study the structure of protoplanetary disks and debris disks around nearby stars. Observations of dust emission at these wavelengths are advantageous because the dust emission is generally optically thin and directly proportional to mass, and contrast with stellar photospheres is not a problem. We are using of several observational facilities, including (1) the Very Large Array (VLA) of the National Radio Astronomy Observatories, (2) the Plateau de Bure Interferometer (PdBI) of the Institut de RadioAstronomie Millimetrique, and (3) the Submillimeter Array (SMA), now under construction by the Smithsonian Astrophysical Observatory and Academia Sinica (Taiwan). In the past year, we have accomplished the following (more details below): (1) We continued work on our 'low resolution' VLA survey of disks in Herbig Ae star and binary systems, primarily to identify candidates for higher resolution follow-up. We have submitted a paper for publication on the detailed analysis of the structure of the disk around CQ Tauri; (2) We completed analysis of our PdBI observations of the debris disk around Vega, and we presented these results at (1) the 199th AAS meeting in Washington, DC, and (2) a symposium in memory of Fred Gillett on Debris Disks and the Formation of Planets, in Tucson, AZ; (3) We continue commissioning observations with the SMA, which include the first ever interferometric images in the 850 micron wavelength band, in preparation for eventually imaging debris disks.

Wilner, David J.↗
NASA NTRS2001

VLA Imaging of Protoplanetary Environments

We continue to use the Very Large Array (VLA) of the National Radio Astronomy Observatories (NRAO) to make high resolution images of thermal emission in the protoplanetary environment of nearby young stars. The VLA provides two unique capabilities. First, the angular resolution for imaging thermal emission is unmatched by any other facility. For the A array, the synthesized beam at a wavelength of 7 mm corresponds to a linear scale similar to the orbital radius of Jupiter at the distance of nearby dark clouds Eke Taurus. Second, the long millimeter wavelengths accessible to the VLA are particularly advantageous at this high resolution since the emission is (almost) entirely optically thin and probes the full disk column, including the innermost regions that remain opaque to shorter wavelengths.

Wilner, David J.↗
NASA NTRS2000

Interferometry for X-Ray Astronomy

With direct imaging, the nature of distant astronomical objects and the physical mechanisms that control them can be constrained and understood. From Galileo's observations of the solar system, to Hubble Space Telescope's imaging of distant galaxies, improved astronomical imaging has always brought scientific understanding. The x-ray band of the spectrum, where exotic objects can have extremely high surface brightness, is ideally suited for high resolution imaging, but has lacked ultra-high quality telescopes. We report a practical x-ray interferometer that features high efficiency, affordable mirrors, adjustable baseline, and can be scaled to a full size observatory. Our prototype system, with just under one millimeter of baseline, created fringes at 1.25 keV with angular resolution of 100 milli-arcseconds. With a larger version of this interferometer in orbit it will be possible to resolve stars, black holes and other compact constituents of the universe. We can study the environments of pulsars, image and then model relativistic blast waves, study the space-time metric near the surface of a black hole, watch the physical formation of astrophysical jets, and study the dynamos of stellar coronae.

Cash, Webster↗
NASA NTRS1998

Giant Molecular Clouds and High-Mass Star Formation in the Milky Way

We are conducting an extensive investigation of high-mass (OB) star formation within the dense cores of giant molecular clouds (GMCS) throughout the first Galactic quadrant of the Milky Way using enhanced resolution Infrared Astronomical Satellite (IRAS) images in combination with high-resolution ground-based observations in millimeter wave molecular transitions and radio continuum. As part of this investigation several resolution enhancement algorithms are applied to the IRAS data, including the HIgh RESolution (HIRES) algorithm developed at the IRAS Processing and Analysis Center (IPAC), as well as others ("pixon" image reconstruction). In addition, as part of a related study, we have completed a large survey of the CO emission in the first Galactic quadrant using the 15-element array detector (QUARRY) with the Five College Radio Astronomy Observatory (FCRAO) 14 m antenna, which provides sampling at an angular resolution of 50", comparable to that attained in the reprocessed IRAS data. Both of these data sets are compared with a sample of ultra-compact (UC) H II regions taken from a high-resolution multi-wavelength (6 and 20 cm) radio survey of the Galactic plane using the NRAO Very Large Array (VLA). Selected regions are observed in 1.3 mm continuum, which has proven to be particularly sensitive to the dust column density. Extensive observations of molecular clouds at high resolution in CO, CS and HCN are combined with the reprocessed IRAS high-resolution images to give a more complete picture of the physical conditions and kinematics of high-mass star forming GMCS. Our goals are to study in detail the morphology, structure, and rate of high-mass star formation within GMCs throughout the Galactic disk from the inner edge of the molecular ring to the outer Galaxy.

Source record↗