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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.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1965

Observational neutrino astronomy.

Observational neutrino astronomy provides detection of nuclear energy generation in Sun, main sequence stars and strong radio sources

STELLAR STRUCTURE↗
NASA NTRS1965

Space astronomy.

Space astronomy, considering UV spectra of Jupiter and Venus, stellar energy distributions, interstellar scattering and X-ray observations

PLANETARY RADIATION↗
NASA NTRS1968

Intergalactic matter.

Intergalactic matter, discussing gaseous component, photon spectrum, cosmic rays, quasi-stellar objects, black body radiation and X ray astronomy

Gould, R. J.↗
NASA NTRS2022

Constraining the Physical Properties of Stellar Coronal Mass Ejections with Coronal Dimming: Application to Far-ultraviolet Data of є Eridani

Coronal mass ejections (CMEs) are a prominent contributor to solar system space weather and might have impacted the Sun's early angular momentum evolution. A signal diagnostic of CMEs on the Sun is coronal dimming: a drop in coronal emission, tied to the mass of the CME, that is the direct result of removing emitting plasma from the corona. We present the results of a coronal dimming analysis of Fe XII 1349 Å and Fe XXI 1354 Å emission from ϵ Eridani ( ϵ Eri), a young K2 dwarf, with archival far-ultraviolet observations by the Hubble Space Telescope's Cosmic Origins Spectrograph. Following a flare in 2015 February, ϵ Eri's Fe XXI emission declined by 81 ± 5%. Although enticing, a scant 3.8 minutes of preflare observations allows for the possibility that the Fe XXI decline was the decay of an earlier, unseen flare. Dimming nondetections following each of three prominent flares constrain the possible mass of ejected Fe XII-emitting (1 MK) plasma to less than a few × 10 15 g. This implies that CMEs ejecting this much or more 1 MK plasma occur less than a few times per day on ϵ Eri. On the Sun, 10 15 g CMEs occur once every few days. For Eri, the mass-loss rate due to CME-ejected 1 MK plasma could be < 0.6 Ṁ Ꙩ well below the star's estimated 30 Ṁ Ꙩ mass-loss rate (wind + CMEs). The order-of-magnitude formalism we developed for these mass estimates can be broadly applied to coronal dimming observations of any star.

Stellar coronal mass ejections↗
NASA NTRS1994

A multiwavelength study of star formation in the L1495E cloud in Taurus

We have carried out a deep (t = 30,000 s) X-ray search of the eastern portion of the L1495 cloud centered on the well-known weak line T Tauri star (WTTS) V410 Tau using the Roentgen Satellite (ROSAT) PSPC. This deep exposure enabled a search for candidate pre-main-sequence (PMS) objects in this cloud to a limit approximately 20 times more sensitive than that typical of the fields examined with the Einstein searches. Despite assertions that the PMS population in Taurus-Auriga is nearly completely known, this Stet survey revealed eight new PMS objects in a region 50 min in diameter, as compared to a previously known stellar population of 12 objects, including deeply embedded Infrared Astronomy Satellite (IRAS) sources. Spectroscopic and photometric observations enable us to place these objects in the H-R diagram. The newly discovered objects are predominantly stars of spectral-type M0 and later, and a large fraction (6/8) appear to be surrounded by circumstellar accretion disks as judged by their infrared excess and H alpha emission. We combined the data for these Stet-discovered objects with extant and new data for the previously identified PMS stars in this region to examine the history of star formation and the frequency distribution of stellar masses in this cloud. If the 'post-ROSAT' population is either complete or representative, we conclude (1) that star formation in L1495 East took place approximately 1 x 10(exp 6) yr ago and that the spread in ages is small; (2) the frequency distribution of masses, N(M), in this apparently coeval group appears to peak near log M = -0.5 (using masses derived from recently published PMS tracks of D'Antona & Mazzitelli and Swenson et al. and to decline toward lower masses. The derived N(log M) for L1495E compares well with the IMF derived from studies of stars in the solar neighborhood, a result which suggests that the Taurus-Auriga clouds are currently producing stars whose mass spectrum approximates the time/space-averaged IMF for the solar neighborhood.

Strom, Karen M.↗
NASA NTRS1994

Stellar-based calibration in the far infrared with application to IRAS Band 4

Because stars emit very small portions of their outputs in the far infrared, using them as calibrators requires precise measurement and correction for filter leaks at shorter wavelengths. Therefore, it is common to base far infrared calibrations on planetary objects such as asteriods. However, asteroids are complex geological bodies whose thermal properties depend on their evolutionary histories as well as on their gross parameters such as mass and composition, making them difficult to model as calibrators. We propose a new method for measuring filter leaks that can be carried out using the end-to-end detector system and therefore allows reliable use of stellar calibrators. We illustrate this method by showing that the Infrared Astronomy Satellite (IRAS) 100 micrometers (Band 4) filters had a short wavelength leak of 14.3% +/- 3.6% on stars similar to alpha Boo, but that there is no detectable leak in the 60 micrometers (Band 3) filters. We derive a calibration for Band 4 from stellar colors in a way that is closely analogous to the calibrations of Bands 1, 2, and 3. With correction for the leak, the stellar-based calibration is virtually identical to the original calibration based on asteroids; this result requires that the spectra of the asteriods for the original calibration differ from greybody behavior between 60 and 100 micrometers by about 10%.

Kirby, D. J.↗
NASA NTRS1990

Astrophysics from the moon; Proceedings of the Workshop, Annapolis, MD, Feb. 5-7, 1990

The present conference on astrophysics from the moon encompasses the study of the Galaxy, external planetary systems, solar physics, stars and stellar evolution, the frontiers of Galactic, extragalactic, and cosmological astronomy, an introduction to lunar-based astronomy, concepts for lunar observatories including high-energy observatories, solar observatories, and observatories for particle astrophysics and gravitational studies. Specific issues addressed include the dynamics of Jovian atmospheres, planetary magnetospheres, flare physics, exobiology and SETI from the lunar farside, and the study of interactive stars, star formation, H II regions in absorption at low frequencies, and normal galaxies. Also addressed are the potential lunar investigation of quasars, the formation epoch, and the large-scale structure of the universe, and observational issues related to X-ray large arrays, optical interferometers, VLF radio astronomy, a UV-solar reflecting coronagraph, and a heavy-nucleus detector.

Mumma, Michael J.↗
NASA NTRS2022

Understanding Structure in Line-Driven Stellar Winds Using Ultraviolet Spectropolarimetry in the Time Domain

The most massive stars are thought to lose a significant fraction of their mass in a steady wind during the main-sequence and blue supergiant phases. This in turn sets the stage for their further evolution and eventual supernova, and preconditions the surrounding medium for all following events, with consequences for ISM energization, chemical enrichment, and dust formation. Understanding these processes requires accurate observational constraints on the mass-loss rates of the most luminous stars, which can also be used to test theories of stellar wind driving. In the past, mass-loss rates have been characterized via collisional emission processes such as optical Hα and free-free radio emission, but these so-called “density squared” diagnostics require correction in the presence of widespread clumping. Recent observational and theoretical evidence points to the likelihood of a ubiquitously high level of such clumping in hot-star winds, but quantifying its effects requires a deeper understanding of the complex dynamics of radiatively driven winds and their stochastic instabilities. Furthermore, large-scale structures initiating in surface anisotropies and propagating throughout the wind can also affect wind driving and alter mass-loss diagnostics. Time series spectroscopy of high resonance-line opacity in the UV, capable of high resolution and high signal-to-noise, are required to better understand these complex dynamics, and more accurately determine mass-loss rates. The proposed Polstar mission (Scowen et al. 2022, this volume) provides the necessary resolution at the Sobolev (∼10 km s −1 ) or sound-speed (∼20 km s −1 ) scale, for over three dozen bright galactic massive stars with signal-to noise an order of magnitude above that of the celebrated MEGA campaign (Massa et al. 1995) of the International Ultraviolet Explorer (IUE), via continuous observations that track propagating structures through the winds in real time. Supporting geometric constraints are provided by the polarimetric capabilities present in all the datasets of such a mission.

Polstar – NASA MIDEX↗
NASA NTRS1974

Crystals for stellar spectrometers

Crystal evaluation as it applies to instrumentation employed in X-ray astronomy is reviewed, and some solutions are offered to problems that are commonly encountered. A general approach for selecting the most appropriate crystals for a given problem is also suggested. The energy dependence of the diffraction properties of (002) PET, (111) Ge, (101) ADP, (101) KAP, and (001) RAP are reported.

Alexandropoulos, N. G.↗
NASA NTRS2018

MoonBEAM: A Beyond Earth-Orbit Gamma-Ray Burst Detector for Multi-Messenger Astronomy

MoonBEAM is a 12U CubeSat concept of deploying gamma-ray detectors in cislunar space to increase gamma-ray burst detections and improve localization precision with the timing triangulation technique. Such an instrument would probe the extreme processes in cosmic collision of compact objects and facilitate multi-messenger time-domain astronomy to explore the end of explore the end of stellar life cycles and black hole formation.

Beyond Earth-Orbit↗
NASA NTRS2020

MoonBEAM: A Beyond Earth-orbit Gamma-ray Burst Detector for Multi-Messenger Astronomy

MoonBEAM is a SmallSat concept of deploying gamma-ray detectors in cislunar space to increase gamma-ray burst detections and improve localization precision with the timing triangulation technique. Such an instrument would probe the extreme processes involved in the cosmic collision of compact objects and facilitate multi-messenger time-domain astronomy to explore the end of explore the end of stellar life cycles and black hole formation.

Hui, Chiumun M.↗
NASA NTRS2022

Measurement of Galactic 26Al with the Compton Spectrometer and Imager

The Compton Spectrometer and Imager (COSI) is a balloon-borne compact Compton telescope de-17signed to survey the 0.2–5 MeV sky. COSI’s energy resolution of ∼0.2% at 1.8 MeV, single-photon reconstruction, and wide field of view make it capable of studying astrophysical nuclear lines, particularly the 1809 keVγ-ray line from decaying Galactic 26Al. Most 26Al originates in massive stars and core-collapse supernova nucleosynthesis, but the path from stellar evolution models to Galaxy-wide emission remains unconstrained. In 2016, COSI had a successful 46-day flight on a NASA super pressure balloon. Here, we detail the first search for the 1809 keV26Al line in the COSI 2016 balloon flight using a maximum likelihood analysis. We find a Galactic 26Al flux of (8.6±2.5) ×10−4ph cm−2s−124 within the Inner Galaxy (|ℓ|≤30◦,|b|≤10◦) with 3.7σ significance above background. Within uncertainties, this flux is consistent with expectations from previous measurements by SPI and COMPTEL. This analysis demonstrates COSI’s powerful capabilities for studies of γ-ray lines and underscores the scientific potential of future compact Compton telescopes. In particular, the next iteration of COSI as a NASA Small Explorer satellite has recently been approved for launch in 2025.

Gamma-ray lines↗
NASA NTRS1976

The supernova: A stellar spectacle

The life of a star, the supernova, related objects and their importance in astronomy and science in general are discussed. Written primarily for science teachers of secondary school chemistry, physics, and earth sciences, the booklet contains a glossary, reference sources, suggested topics for discussion, and projects for individual or group assignment.

Astronomy↗