Search NASA⌕ Search

SEARCH · Search NASA

Results for “comets”

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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Recurrent Activity from Active Asteroid (248370) 2005 QN 173 : A Main-belt Comet

We present archival observations of main-belt asteroid (248370) 2005 QN 173 (also designated 433P) that demonstrate this recently discovered active asteroid (a body with a dynamically asteroidal orbit displaying a tail or coma) has had at least one additional apparition of activity near perihelion during a prior orbit. We discovered evidence of this second activity epoch in an image captured 2016 July 22 with the DECam on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. As of this writing, (248370) 2005 QN 173 is just the eighth active asteroid demonstrated to undergo recurrent activity near perihelion. Our analyses demonstrate (248370) 2005 QN 173 is likely a member of the active asteroid subset known as main-belt comets, a group of objects that orbit in the main asteroid belt that exhibit activity that is specifically driven by sublimation. We implement an activity detection technique, wedge photometry, that has the potential to detect tails in images of solar system objects and quantify their agreement with computed antisolar and antimotion vectors normally associated with observed tail directions. We present a catalog and an image gallery of archival observations. The object will soon become unobservable as it passes behind the Sun as seen from Earth, and when it again becomes visible (late 2022) it will be farther than 3 au from the Sun. Our findings suggest (248370) 2005 QN 173 is most active interior to 2.7 au (0.3 au from perihelion), so we encourage the community to observe and study this special object before 2021 December.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Autonomous real-time detection of plumes and jets from moons and comets

Dynamic activity on the surface of distant moons, asteroids, and comets can manifest as jets or plumes. These phenomena provide information about the interior of the bodies and the forces (gravitation, radiation, thermal) they experience. Fast detection and follow-up study is imperative since the phenomena may be time-varying and because the observing window may be limited (e.g., during a flyby). We have developed an advanced method for real-time detection of plumes and jets using onboard analysis of the data as it is collected. In contrast to prior work, our technique is not restricted to plume detection from spherical bodies, making it relevant for irregularly shaped bodies such as comets. Further, our study analyzes raw data, the form in which it is available on board the spacecraft, rather than fully processed image products. In summary, we contribute a vital assessment of a technique that can be used on board tomorrow's deep space missions to detect, and respond quickly to, new occurrences of plumes and jets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16 O-rich (associated with refractory inclusions) and 16 O-poor (associated with chondrules). Both the 16 O-rich and 16 O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16 O-rich to 16 O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

CoMet

CoMet is an application for finding epistatic and pleiotropic relationships from large quantities of genomic data. It solves these large combinatorial problems on GPU-accelerated systems with thousands of compute nodes. Its methods include the 2-way Proportional Similarity method, the Custom Correlation Coefficient and the DUO method. CoMet was developed at the Oak Ridge Leadership Computing Facility in collaboration with the Computational Biology and Bioinformatics Group at Oak Ridge National Laboratory.

Joubert, WayneD↗
DOE OSTI2021

Chemical Composition of Outbursting Comet C/2015 ER61 (PanSTARRS)

Comet C/2015 ER61 (PanSTARRS) is a long-period Oort cloud comet whose favorable approach to the inner parts of the solar system in 2017 April–May enabled us to characterize its primary volatile composition using the iSHELL spectrograph mounted on the 3 m NASA Infrared Telescope Facility (IRTF) on Maunakea, Hawaii. We used three iSHELL settings (covering ~2.8–5.2 μm) to sample fluorescent emissions from H{sub 2}O, OH, CH{sub 3}OH, HCN, C{sub 2} H{sub 2}, NH{sub 3}, CO, CH{sub 4}, C{sub 2}H{sub 6}, H{sub 2}CO, and OCS on multiple dates ranging from UT 2017 April 15 (shortly after its April 4 outburst) to May 13, nearly 30 days before the detection of its double nucleus. Our observations also offered the opportunity to obtain sensitive 3σ upper limits for cyanoacetylene (HC{sub 3}N). We report rotational temperatures (T{sub rot}), production rates (Qs), abundance (mixing) ratios (relative to H{sub 2}O and C{sub 2}H{sub 6}), and spatial distributions in the coma. ER61 exhibits variability in production rates of many species on short (day-to-day) and long (pre- versus post-perihelion) timescales. The relative abundances of these volatile species remained consistent within uncertainties during our pre-perihelion observations but tended to decrease during our post-perihelion observations (with the exception of CH{sub 3}OH and HCN). The short-timescale variability in the production rates of these volatiles could be due to diurnal effects (over the course of the rotation of the nucleus) and/or the effect of its outburst. The decrease in the production rates and hence the mixing ratios in some volatiles in post-perihelion dates could be due to the presence of seasonal effects in ER61.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1968

The physics of comet tails.

Physics of comet tails, discussing structure and orientation, plasma and dust composition, space probe rendezvous, artificial comet and simulation

Brandt, J. C.↗
NASA NTRS1972

Infrared Measures of Comets

Infrared observations of two comets, 1969g and 1969i, are presented. In both comets the infrared flux appears to be of thermal origin. The structure of the sources as well as the temperature, emissivity, and composition of the radiating material are discussed.

Lee, T.↗
NASA NTRS1972

Photometry of comets

The photometric observations of comets are discussed in terms of providing profiles of the whole comet.

Miller, F.↗
NASA NTRS1972

Spectroscopic observations of comets

The value of C-12/C-13 for the Comets Tago-Sato-Kosaka and Bennett was investigated. The values for both comets are presented in spectrographs.

Owen, T. C.↗
NASA NTRS1972

Present Understanding of Comets

An assessment of cometary research from 1970 to 1972 was made. Particular attention was given to the Lyman alpha halo of Comets Tago-Sato-Kosaka, Bennett, and Encke, and the large gas productions of these comets. The icy conglomerate and sand bank models are discussed in detail.

Delsemme, A. H.↗
NASA NTRS1972

Photographic Observations of Comet Bennett, 1970II

Direct photography of Comet Bennett with a range of focal lengths shows structure in the coma and strong Type 1 and Type 2 tails. The Type 1 tail shows motion in 15 minutes. The inner coma contains spiral-shaped jets of a type observed visually on occasion in the past but not photographed before. The spiral shape is apparently due to the rotation of the nucleus. On the assumption that the outward velocity of the jets is 0.6 km/sec, as estimated by Delsemme, a rotation period of 1.4 to 1.5 days is derived for the nucleus. The rotation is direct (in the sense of the comet's orbital motion).

Larson, S. M.↗
NASA NTRS1973

A model of the physical properties of comet Encke

The available observational data on periodic comet Encke were collected and interpreted in order to construct a model of the comet. The model is intended for use in the design of scientific experiments and spacecraft systems to be used on future missions to Encke. Numerical values and ranges of uncertainty are given for all of the important structural, compositional, and photometric parameters with references to the original research from which these were calculated or estimated.

Taylor, F. W.↗
NASA NTRS1972

Photographic observations of Comet Bennett, 1970II.

Direct photography of Comet Bennett with a range of focal lengths shows structure in the coma and strong Type I and Type II tails. The Type I tail shows motion in 15 minutes. The inner coma contains spiral-shaped jets of a type observed visually on occasion in the past but not photographed before. The spiral shape is apparently due to the rotation of the nucleus. On the assumption that the outward velocity of the jets is 0.6 km/sec, as estimated by Delsemme, a rotation period of 1.4-1.5 days is derived for the nucleus. The rotation is direct (i.e., in the sense of the comet's orbital motion).

Larson, S. M.↗