Dust Stream Research Articles

Symmetrical vortices and laminar dust flow induced by an intense electron beam interacting with a strongly coupled dusty plasma

A strongly coupled quasi-two-dimensional dusty plasma confined electrostatically in the plasma sheath of a radio frequency (RF) plasma is irradiated by a collimated and mono-energetic pulsed electron beam (e-beam) with an energy of 13 keV and a high peak current per pulse of 30 mA. A stream of rapidly moving charged dust particles is created inside the dust crystal due to the drag force of the electrons in the e-beam. The dust flow is split into two symmetrical branches when it reaches the boundary of the round dust crystal, each following the limit of the circular confining region. This results in the formation of a double vortex flow pattern with the dust particles being transported along the irradiation direction and then aside, eventually back to the entrance position of the e-beam. The observed flow regime is laminar at all times, with the speed in the central region increasing up to 12 mm s−1 in the first 200 ms and then diminishing gradually to a steady value of about 5–6 mm s−1 during a stress relaxation time period of 360 ms. The vorticity follows a similar trend with peak values −3.8 and 3.8 s−1 and steady state values between −2.5 and 2.5 s−1 in the two symmetrical vortices. Time-resolved particle-image-velocimetry and particle-tracking-velocimetry are used to characterize the flow. Molecular dynamics simulations confirm qualitatively the experimental observations showing dust stream and double vortex formation.

Coma and tail of Comet 67P/Churyumov–Gerasimenko during the 2021–2022 apparition

ABSTRACT We present results on the global activity of comet 67P/Churyumov–Gerasimenko (67P), the ROSETTA target, during its first perihelion passage after the mission and after an encounter with planet Jupiter. 67P was observed by broad-band filter imaging at 33 epochs during 2021 May 21 to 2022 June 1. The mean radial flux profiles suggest that ‘equilibrium’ conditions for the dust flow in the coma existed from around perihelion until about 100 d thereafter. We propose a scenario for the smaller and larger radial exponents, measured before and after the ‘equilibrium’ phase. Four coma fans with possible source regions at +40°, –10°, –50°, and –70° latitude on the nucleus are identified. The three fans at southern latitudes may be identical with fan sources seen during post-perihelion in 2015–2016. The rotation axis of 67P may not have changed at all or at least not much (<5°) from the orientation measured during the Rosetta mission at the comet. The dust streamers in the coma originated from observed coma fans, containing mostly dust emitted within days to weeks before observation. Two dust streamers, a long- and a short-lasting one, contained heavy dust grains from emission periods hundreds of days before perihelion. Similar emission periods are obtained for the dust seen in the tail region of the comet. Similarities and differences in the dust activity during the recent apparition with that of the Rosetta mission at the comet are found.

Ulysses spacecraft in situ detections of cometary dust trails.

The Ulysses spacecraft was launched in 1990 and, after a Jupiter swing-by in 1992, became the first interplanetary spacecraft orbiting the Sun on a highly inclined trajectory with an inclination of [Formula: see text]. The spacecraft was equipped with an impact ionization dust detector which provided 17 years of in situ dust measurements in interplanetary space from 1990 to 2007. Cometary meteoroid streams (also referred to as trails) exist along the orbits of comets, forming fine structures of the interplanetary dust cloud. We use the Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model (Soja RH et al. 2015 Characteristics of the dust trail of 67P/Churyumov-Gerasimenko: an application of the IMEX model. Astron. Astrophys. 583, A18. (doi:10.1051/0004-6361/201526184)) to predict cometary stream traverses by Ulysses and re-analyse the Ulysses dust dataset in order to identify impacts of cometary stream particles detected during such trail traverses. We identify 19 particles compatible with three Ulysses trail traverses on 12 March 1995, 25-27 April 2001 and 16-19 May 2001. The particle origin is compatible with up to five comets, i.e. 10P/Tempel 2, 146P/Shoemaker-LINEAR, 267P/LONEOS and possibly 45P/Honda-Mrkos-Pajdušáková and P/1999 RO28 (LONEOS). We find a dust spatial density in these trails of approximately [Formula: see text]. The radii of the detected cometary stream particles derived from the dust instrument calibration are in the micrometre range. The in situ analysis of meteoroid trail particles in space, which can be traced back to their source bodies, opens a new opportunity for remote compositional analysis of comets and asteroids without the necessity to send a spacecraft to or even land on these celestial bodies, opening new opportunities for future space missions equipped with in situ dust analyzers. This article is part of the theme issue 'Dust in the Solar System and beyond'.

PHANGS–JWST First Results: Massive Young Star Clusters and New Insights from JWST Observations of NGC 1365

A primary new capability of JWST is the ability to penetrate the dust in star-forming galaxies to identify and study the properties of young star clusters that remain embedded in dust and gas. In this Letter we combine new infrared images taken with JWST with our optical Hubble Space Telescope (HST) images of the starbursting barred (Seyfert2) spiral galaxy NGC 1365. We find that this galaxy has the richest population of massive young clusters of any known galaxy within 30 Mpc, with ∼30 star clusters that are more massive than 106 M ⊙ and younger than 10 Myr. Sixteen of these clusters are newly discovered from our JWST observations. An examination of the optical images reveals that 4 of 30 (∼13%) are so deeply embedded that they cannot be seen in the Hubble I band (A V ≳ 10 mag), and that 11 of 30 (∼37%) are missing in the HST B band, so age and mass estimates from optical measurements alone are challenging. These numbers suggest that massive clusters in NGC 1365 remain completely obscured in the visible for ∼1.3 ± 0.7 Myr and are either completely or partially obscured for ∼3.7 ± 1.1 Myr. We also use the JWST observations to gain new insights into the triggering of star cluster formation by the collision of gas and dust streamers with gas and dust in the bar. The JWST images reveal previously unknown structures (e.g., bridges and overshoot regions from stars that form in the bar) that help us better understand the orbital dynamics of barred galaxies and associated star-forming rings. Finally, we note that the excellent spatial resolution of the NIRCAM F200W filter provides a better way to separate barely resolved compact clusters from individual stars based on their sizes.

Phenomenology of plume–surface interactions and preliminary results from the Tianwen-1 landing crater on Mars

The plume–surface interaction (PSI) is a common phenomenon that describes the environment surrounding the landers resulting from the impingement of hot rocket exhaust on the regolith of planetary bodies. The PSI will cause obscuration, erosion of the planetary surface, and high-speed spreading of dust or high-energy ejecta streams, which will induce risks to a safe landing and cause damage to payloads on the landers or to nearby assets. Safe landings and the subsequent scientific goals of deep-space exploration in China call for a comprehensive understanding of the PSI process, including the plume flow mechanics, erosion mechanism, and ejecta dynamics. In addition, the landing crater caused by the plume provides a unique and insightful perspective on the understanding of PSI. In particular, the PSI can be used directly to constrain the composition, structure, and mechanical properties of the surface and subsurface soil. In this study, we conducted a systematic review of the phenomenology and terrestrial tests of PSI: we analyzed the critical factors in the PSI process and compared the differences in PSI phenomena between lunar and Martian conditions; we also reviewed the main erosion mechanisms and the evolution and development of terrestrial tests on PSI. We discuss the problems with PSI, challenges of terrestrial tests, and prospects of PSI, and we show the preliminary results obtained from the landing crater caused by the PSI of Tianwen-1. From analysis of the camera images and digital elevation model reconstructions, we concluded that the landing of Tianwen-1 caused the deepest crater (depth > 40 cm) on a planetary surface reported to date and revealed stratigraphic layers in the subsurface of Martian soil. We further constrained the lower bounds of the mechanical properties of Martian soil by a slope stability analysis of the Tianwen-1 landing crater. The PSI may offer promising opportunities to obtain greater insights into planetary science, including the subsurface structure, mineral composition, and properties of soil.

Valorization of Quercus suber L. Bark as a Source of Phytochemicals with Antimicrobial Activity against Apple Tree Diseases.

Cork, an anatomic adaptation of the bark of Quercus suber L. through its suberization process, finds its main application in the production of bottle stoppers. Its processing results in a large waste stream of cork fragments, granulates, and dust, which may be susceptible to valorization. The work presented here explored the use of its extracts to inhibit the growth of phytopathogenic microorganisms associated with apple tree diseases. The in vitro antimicrobial activity of cork aqueous ammonia extract was assayed against four fungi, viz. Monilinia fructigena and M. laxa (brown rot), Neofussicoccum parvum (dieback), and Phytophthora cactorum (collar and root rot), and two bacteria, viz. Erwinia amylovora and Pseudomonas syringae pv. syringae, either alone or in combination with chitosan oligomers (COS). Effective concentration values of EC90 in the 675-3450 μg·mL-1 range, depending on the fungal pathogen, were obtained in growth inhibition tests, which were substantially improved for the conjugate complexes (340-801 μg·mL-1) as a result of strong synergism with COS. Similar enhanced behavior was also observed in antibacterial activity assays, with MIC values of 375 and 750 μg·mL-1 for the conjugate complexes against P. syringae pv. syringae and E. amylovora, respectively. This in vitro inhibitory activity was substantially higher than those exhibited by azoxystrobin and fosetyl-Al, which were tested for comparison purposes, and stood out among those reported for other natural compounds in the literature. The observed antimicrobial activity may be mainly attributed to the presence of glycerin and vanillic acid, identified by gas chromatography-mass spectroscopy. In the first step towards in-field application, the COS-Q. suber bark extract conjugate complex was further tested ex situ against P. cactorum on artificially inoculated excised stems of the 'Garnem' almond rootstock, achieving high protection at a dose of 3750 μg·mL-1. These results suggest that cork industrial leftovers may, thus, be a promising source of bioactive compounds for integrated pest management.

Antarctic micrometeorite composed of CP and CS IDP‐like material: A micro‐breccia originated from a partially ice‐melted comet‐like small body

AbstractAsteroids and comets are thought to form in the inner and outer solar systems, respectively. Chondritic porous and smooth interplanetary dust particles (CP IDPs and CS IDPs, respectively) in the stratosphere are regarded as dust grains from comets and hydrated asteroids, respectively. Here, we describe an Antarctic micrometeorite (AMM) composed of lithologies of both CP and CS IDPs. In addition to the CS IDP‐like compact lithology that experienced severe aqueous alteration, the CP IDP‐like porous lithology shows evidence of very weak aqueous alteration. The structure of the organic matter in the porous lithology varies from that in the CP IDPs to aromatic‐rich organic matter. In contrast, the structure of the organic matter in the compact lithology is homogenous, which is consistent with higher degrees of aqueous alteration. Its structure is more similar to that of CP IDPs and Wild 2 samples than that of meteoritic insoluble organic matter, suggesting that the compact lithology formed from the porous lithology. Some CP IDPs are related to cometary dust streams, such as those originating from 26P/Grigg‐Skjellerup. In addition, the presence of this AMM indicates an additional origin of the CP IDPs and their equivalent AMMs. The mineralogy and organic chemistry of this AMM suggest that its parent body was composed of the same building blocks as those of the comets, and later experienced incomplete aqueous alteration. The AMM probably formed as microbreccia in the regolith layer composed of materials from a CP IDP‐like crust and a hydrated interior.

Climatology of atmospheric dust corridors in the Middle East based on satellite data

Dust aerosols can sometimes extend thousands of kilometers continuously in the atmosphere. In this study, we refer to these dust streams, as Atmospheric Dust Corridors (ADCs). This study aims to identify ADCs by an automated algorithm and investigate their temporal and spatial characteristics in the Middle East. In order to do this, the Aerosol Optical Depth (AOD) and Angstrom Exponent (AE) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) (Aqua) were obtained on a daily scale at a resolution of 1*1° between 2003 and 2020. In this study, observations with AOD above 0.3 and AE below 0.75 were considered as dust aerosols. After determining a set of conditions, an algorithm was developed to identify the ADCs automatically. In the first step, the dust masses were identified using the connected components labeling method, and the largest dust mass was selected from each day. Then, a set of conditions were examined such as geometric shape and motion of the dust mass (based on wind data). As a result, we identified 281 ADCs and classified them according to their direction of movement. We found 33% cases of ADCs that flow toward the west, 19% cases that flow toward the east, 36% cases that flow toward the south, and 12% cases that flow toward the north. All the directions had the highest frequency in September, April, and March, whereas February, November and December had the lowest frequency. Spatially, the highest frequency can be seen around 45°E over Saudi Arabia, Iraq, and Syria. Western and southern ADCs are primarily found in the Arabian Peninsula and in Iraq, Syria, southern Iran, southern Afghanistan, and northern Pakistan, while northern and eastern ADCs are primarily found in northern Africa (Sudan and Chad, Niger, and Libya). May is important for western ADCs, September for southern ADCs, and April for eastern and northern ADCs. According to the Mann-Kendal test, no significant trends were observed on a monthly or annual basis during the studied period.

Study of the Effectiveness of Innovative Air Purification Systems Used in the Design of Road Construction Enterprises

The article shows which features of the production of road construction materials are taken into account design of road industry enterprises. Submitted by the authors description of human exposure to dust. It is specified that in Russian Federation usually uses graviometric analysis applied to all dust contained in the entire volume of the room. The authors suggest reduce industrial emissions by installing innovative air purification systems on the discharge pipes from dusty road production equipment to reduce the likelihood of dispersion of polluting components of dust and air streams in the air of the working area.

Tissue Analysis in Filters of Dust and Gas Cleaning Systems of Cement Production

Dust collection in the process of cement production is especially important for Fergana due to the increase in the number of cement plants, since this is one of the areas of technogenic pollution of the environment. Therefore, it is important to capture the dust that gets into the air during this process. The article analyzes the materials of fabrics used in bag filters used at cement plants in the region. The analysis of works on the state of the synthetic filtering apparatus, which removes air from the dust stream, is presented. The studied methods and procedure of filter regeneration without tissue damage are presented.

Analysis of the Effects of Dynamic Alloying on the Structure of Aluminium and its Alloys

The dynamic alloying of aluminum and its alloy with a high-speed stream of silicon carbide (SiC) particles simulates the effect of a stream of cosmic dust on spacecraft materials. The study showed a structure change in the volume of aluminum and its alloy and the formation of new structural elements. The transformation of the structure during dynamic alloying leads to a change of the composition and mechanical properties of the matrix material.

Properties of technical aluminum under the effect of dynamic alloying

Dynamic alloying in the mode of super-deep penetration (SDP) allows us to evaluate the effects that occur in the materials of the spacecraft when interacting with high-speed streams of cosmic dust. The results of the experiments are presented, confirming that dynamic alloying in the SDP mode creates anisotropy in a solid body and leads to a change in physical properties (electrical resistance, electron work function). The dynamic alloying increased the anisotropy of electrical resistance in technical aluminum 99.7% Al in 2.05 times (105%), led to a decrease of the electrical resistance in the longitudinal direction by 16% and increase in the transverse direction by 41%.

Fast, computer‐assisted detection of dust and debris impact craters on Stardust interstellar foils

AbstractThe NASA Stardust Interstellar Dust collection provides our current best sample set for direct laboratory analysis of dust grains from the contemporary interstellar dust stream. While a handful of likely interstellar dust grains were identified within the silica aerogel collection media, interstellar dust also impacted Al foils covering the collector frame. Locating these rare impacts requires labor‐intensive collection and examination of tens of thousands of high‐resolution SEM images. Here, we implement a Python‐based algorithm to dramatically reduce the human time investment needed to locate impact craters. The algorithm employs a circular Hough transform to identify circular features in the foil images, followed by several tests to detect characteristic morphological features of impact craters—a dark center and a bright rim, with inclusion of multi‐core processing capabilities to significantly increase processing speed. For most data sets, the code produced a pool of potential crater candidates in 1–5% of the input images, producing a more manageable subset of images for a human expert to review. We used this code to locate 31 impact craters across 12 Stardust interstellar foils, 25 of which were located on three adjacent foils, I1008W,1, I1009N,1, and I1020W,1. Many impacts on these foils formed shallow, oblique craters, with residue compositions consistent with solar cell glass and orientations consistent with debris ejected from the spacecraft solar cells. The code can be integrated into future searches for Stardust interstellar grain impacts and can be implemented as a general utility for dust impact studies on spacecraft materials.

A cosmic dust detection suite for the deep space Gateway

• A model dust detector payload is described for deployment near the Moon. • An ideal lunar platform would be the proposed Lunar Gateway. • The payload has active and passive components. • It would measure dust identifying the cometary, asteroidal and interstellar fluxes. The decade of the 2020s promises to be when humanity returns to space beyond Earth orbit, with several nations trying to place astronauts on the Moon, before going further into deep space. As part of such a programme, NASA and partner organisations, propose to build a Deep Space Gateway in lunar orbit by the mid-2020s. This would be visited regularly and offer a platform for science as well as for human activity. Payloads that can be mounted externally on the Gateway offer the chance to, amongst other scientific goals, monitor and observe the dust flux in the vicinity of the Moon. This paper looks at relevant technologies to measure dust which will impact the exposed surface at high speed. Flux estimates and a model payload of detectors are described. It is predicted that the flux is sufficient to permit studies of cometary vs. asteroidal dust and their composition, and to sample interstellar dust streams. This may also be the last opportunity to measure the natural dust flux near the Moon before the current, relatively pristine environment, is contaminated by debris, as humanity’s interest in the Moon generates increased activity in that vicinity in coming decades.

Modelling cometary meteoroid stream traverses of the Martian Moons eXploration (MMX) spacecraft en route to Phobos

The Martian Moons Exploration (MMX) spacecraft is a JAXA mission to Mars and its moons Phobos and Deimos. MMX will be equipped with the Circum-Martian Dust Monitor (CMDM) which is a newly developed light-weight (mathrm {650,g}) large area (1,mathrm {m}^{2}) dust impact detector. Cometary meteoroid streams (also referred to as trails) exist along the orbits of comets, forming fine structures of the interplanetary dust cloud. The streams consist predominantly of the largest cometary particles (with sizes of approximately 100,mu mathrm { m} to 1 cm) which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun. The Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model is a new and recently published universal model for cometary meteoroid streams in the inner Solar System. We use IMEX to study the detection conditions of cometary dust stream particles with CMDM during the MMX mission in the time period 2024 to 2028. The model predicts traverses of 12 cometary meteoroid streams with fluxes of 100,mu mathrm { m} and bigger particles of at least 10^{-3},mathrm {m}^{-2},mathrm {day}^{-1} during a total time period of approximately 90 days. The highest flux of 0.15,mathrm {m}^{-2},mathrm {day}^{-1} is predicted for comet 114P/Wiseman-Skiff in October 2026. With its large detection area and high sensitivity CMDM will be able to detect cometary meteoroid streams en route to Phobos. Our simulation results for the Mars orbital phase of MMX also predict the occurrence of meteor showers in the Martian atmosphere which may be observable from the Martian surface with cameras on board landers or rovers. Finally, the IMEX model can be used to study the impact hazards imposed by meteoroid impacts onto large-area spacecraft structures that will be particularly necessary for crewed deep space missions.

Helios spacecraft data revisited: detection of cometary meteoroid trails by following in situ dust impacts

Context. Cometary meteoroid trails exist in the vicinity of comets, forming a fine structure of the interplanetary dust cloud. The trails consist predominantly of the largest cometary particles (with sizes of approximately 0.1 mm–1 cm), which are ejected at low speeds and remain very close to the comet orbit for several revolutions around the Sun. In the 1970s, two Helios spacecraft were launched towards the inner Solar System. The spacecraft were equipped with in situ dust sensors which measured the distribution of interplanetary dust in the inner Solar System for the first time. Recently, when re-analysing the Helios data, a clustering of seven impacts was found, detected by Helios in a very narrow region of space at a true anomaly angle of 135 ± 1°, which the authors considered as potential cometary trail particles. However, at the time, this hypothesis could not be studied further. Aims. We re-analyse these candidate cometary trail particles in the Helios dust data to investigate the possibility that some or all of them indeed originate from cometary trails and we constrain their source comets. Methods. The Interplanetary Meteoroid Environment for eXploration (IMEX) dust streams in space model is a new and recently published universal model for cometary meteoroid streams in the inner Solar System. We use IMEX to study the traverses of cometary trails made by Helios. Results. During ten revolutions around the Sun, the Helios spacecraft intersected 13 cometary trails. For the majority of these traverses the predicted dust fluxes are very low. In the narrow region of space where Helios detected the candidate dust particles, the spacecraft repeatedly traversed the trails of comets 45P/Honda-Mrkos-Pajdušáková and 72P/Denning-Fujikawa with relatively high predicted dust fluxes. The analysis of the detection times and particle impact directions shows that four detected particles are compatible with an origin from these two comets. By combining measurements and simulations we find a dust spatial density in these trails of approximately 10−8–10−7 m−3. Conclusions. The identification of potential cometary trail particles in the Helios data greatly benefited from the clustering of trail traverses in a rather narrow region of space. The in situ detection and analysis of meteoroid trail particles which can be traced back to their source bodies by spacecraft-based dust analysers provides a new opportunity for remote compositional analysis of comets and asteroids without the necessity to fly a spacecraft to or even land on those celestial bodies. This provides new science opportunities for future missions like DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science), Europa Clipper, and the Interstellar Mapping and Acceleration Probe.

INCREASING OF RESOURCE OF SUPERCHARGERS' AND FANS' VEINS WITH WELDING METHODS

Influence of gas and dust stream's parameters on wear durability of protection elements (of veins and bearing disk) of fans and supercharges is analyzed. Data about wear pattern of the most charged details of labor devices, which are operated in conditions of thermal power and mining plants is given. The results of direct measurements of geometric dimensions' loss, the shape of blades and the bearing (central) disk were accounted until the moment of their replacement (renovation). Traditional measuring instruments and ultrasonic thickness gauge UT-31 were used. Beginning of wear with the smallest defects in the surface layer (irregularities, depressions, surface cracks, local bumps, etc.) is found. First of all, the inlet edge of the scapula on the side of the suction pipe is worn. The measurements of blade showed wear of the inlet edge to its complete destruction, blade decreased by 30 mm in length. In case of a two-layer structure, there is a «stripping» of base metal of the blade and further wear of the part is accelerated. The wear of the deposited layer up to 3 mm (25% of blade thickness) is critical for further operation. Considering the different mode of operation of the devices and the uneven nature of the wear, a differentiated approach is proposed when choosing the composition of the metal for hardening and facing of the most worn surfaces. As reserves for increasing of inter-repair periods, arc surfacing with adding of different carbide-forming agents (in unequal amounts by zones) and using of surfaced bimetallic sheets are named. Spherical granules of tungsten carbides instead of crushed particles and the working bimetal layer molded in composition as durable high-chromium cast iron are recommended for reinforcement.

Criterion for evaluation of erosion of aviation engine parts from polymer composite materials

A criterion is proposed for assessing the reliability of parts made of polymer composite materials in the event of sand and dust entering the compressor during take-off and landing. Conducting erosion tests with a concentration of abrasive particles corresponding to a conventional dust stream is practically impossible due to their long duration. When conducting tests with a high concentration that is several orders of magnitude higher than the concentration of a conventional stream, the reliability of the estimate is reduced due to the need to extrapolate the results to a large resource. Therefore, to improve the accuracy of the assessment of the erosion resistance of engine parts from polymer composite materials, it is proposed to conduct periodic measurements of the thickness of the part during operation. By calculating the dynamic eigenfrequencies and oscillation shapes and maximum static stresses, the critical thickness of the part is established, below which its eigenfrequency approaches the dangerous rotor harmonics.

The nuclear region of NGC 613 – I. Multiwavelength analysis

ABSTRACT In this paper, we report a detailed study with a variety of data from optical, near-infrared, X-ray, and radio telescopes of the nuclear region of the galaxy NGC 613 with the aim of understanding its complexity. We detected an extended stellar emission in the nucleus that, at first, appears to be, in the optical band, two stellar nuclei separated by a stream of dust. The active galactic nucleus (AGN) is identified as a variable point-like source between these two stellar components. There is a central hard X-ray emission and an extended soft X-ray emission that closely coincides with the ionization cone, as seen in the [O iii]λ5007 emission. The centroid of the [O i]λ6300 emission does not coincide with the AGN, being shifted by 0.24 arcsec towards the ionization cone; this shift is probably caused by a combination of differential dust extinction together with emission and reflection in the ionization cone. The optical spectra extracted from the central region are typical of low-ionization nuclear emission-line regions. We also identify 10 H ii regions, eight of them in a star-forming ring that is visible in Br γ, [Fe ii]λ16436, and molecular CO(3-2) images observed in previous studies. Such a ring also presents weak hard X-ray emission, probably associated with supernova remnants, not detected in other studies. The position of the AGN coincides with the centre of a nuclear spiral (detected in previous works) that brings gas and dust from the bar to the nucleus, causing the high extinction in this area.

Interstellar dust in the solar system: model versus in situ spacecraft data

Context. In the early 1990s, contemporary interstellar dust penetrating deep into the heliosphere was identified with the in situ dust detector on board the Ulysses spacecraft. Later on, interstellar dust was also identified in the data sets measured with dust instruments on board Galileo, Cassini, and Helios. Ulysses monitored the interstellar dust stream at high ecliptic latitudes for about 16 yr. The three other spacecraft data sets were obtained in the ecliptic plane and cover much shorter time intervals. Aims. To test the reliability of the model predictions, we compare previously published in situ interstellar dust measurements, obtained with these four spacecraft, with predictions of an advanced model for the dynamics of interstellar dust in the inner solar system (Interplanetary Meteoroid environment for EXploration; IMEX). Methods. Micrometer and sub-micrometer-sized dust particles are subject to solar gravity, radiation pressure and the Lorentz force on a charged dust particle moving through the interplanetary magnetic field. These forces lead to a complex size-dependent flow pattern of interstellar dust in the planetary system. The IMEX model was calibrated with the Ulysses interstellar dust measurements and includes these relevant forces. We study the time-resolved flux and mass distribution of interstellar dust in the solar system. Results. The IMEX model agrees with the spacecraft measurements within a factor of 2–3, including time intervals and spatial regions not covered by the original model calibration with the Ulysses data set. The model usually underestimates the dust fluxes measured by the space missions which were not used for the model calibration, i.e. Galileo, Cassini, and Helios. Conclusions. A unique time-dependent model, IMEX is designed to predict the interstellar dust fluxes and mass distributions for the inner and outer solar system. The model is suited to study dust detection conditions for past and future space missions.