scholarly journals Fractal Dust Grains

1989 ◽  
Vol 135 ◽  
pp. 337-342
Author(s):  
Edward L. Wright
Keyword(s):  
Interstellar Medium ◽  
Analytical Calculation ◽  
Far Infrared ◽  
Interplanetary Dust ◽  
Infrared Emission ◽  
Dipole Approximation ◽  
Extinction Curve ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Emission Efficiency

Dust particles in the interstellar medium are almost certainly not spherical or any other shape which allows an analytical calculation of the extinction curve, even in the Rayleign limit. Particles in soot and interplanetary dust particles are aggregates formed by subclusters which stick together. This paper uses the discrete dipole approximation (DDA) to compute the absorption and extinction curves for fractal shapes generated by this clustering process. For fractals made from graphite the UV extinction curve shows a bump near the observed 220 nm feature, and a far infrared emission efficiency many times greater than that for spheres.

ERE from Graphene Oxide in the ISM. A possible link to IOM?

2020 ◽  
Author(s):  
Peter Sarre
Keyword(s):  
Graphene Oxide ◽  
Organic Material ◽  
Interstellar Dust ◽  
Emission Spectra ◽  
Optical Emission ◽  
Interplanetary Dust ◽  
Infrared Emission ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Infrared Space Observatory

<p>Dust particles play a major role in the formation, evolution and chemistry of interstellar clouds, stars, and planetary systems. Commonly identified forms include amorphous and crystalline carbon-rich particles and silicates. Also present in many astrophysical environments are polycyclic aromatic hydrocarbons (PAHs), detected through their infrared emission, and which are essentially small flakes of graphene. Astronomical observations over the past four decades have revealed a widespread unassigned ‘extended red emission’ (ERE) feature which is attributed to luminescence of dust grains. A luminescence feature with similar characteristics to ERE has been found in organic material in interplanetary dust particles and carbonaceous chondrites.  </p> <p>There is a strong similarity between laboratory optical emission spectra of graphene oxide (GO) and ERE, leading to this proposal that emission from GO nanoparticles is the origin of ERE and that heteroatom-containing PAH structures are a significant component of interstellar dust. The proposal is supported by infrared emission features detected by the <em>Infrared Space Observatory (ISO)</em> and the <em>Spitzer Space Telescope</em>.  </p> <p>Insoluble Organic Material (IOM) has a chemical structure with some similarities to graphene oxide.  It is suggested this may contribute to the discussion as to whether IOM has an origin in the interstellar medium or the solar nebula, or some combination.</p>

scholarly journals Applicability of A1-term Method to the Scattering by Irregularly Shaped Interplanetary Dust Grains

1996 ◽  
Vol 150 ◽  
pp. 423-426 ◽  
Author(s):  
Hajime Okamoto
Keyword(s):  
Incident Wave ◽  
Mie Theory ◽  
Interplanetary Dust ◽  
Dipole Approximation ◽  
Dust Particles ◽  
Dipole Polarizability ◽  
Size Parameter ◽  
Interplanetary Dust Particles ◽  
Equivalent Radius ◽  
Single Dipole

AbstractThe first scattering coefficient (a1-term) in Mie theory is introduced to determine the dipole polarizability used in the discrete dipole approximation (DDA) to calculate the scattering properties of the cluster of spheres in order to improve our understanding of interplanetary dust particles. In this method, each sphere in a cluster is replaced by a single dipole. The accuracy of this method is tested for a few spheres in contact. It is confirmed that the a1-term method is superior to other types of DDA and is particularly suitable for the case when the particles are placed randomly. By using this method, it becomes possible to treat large cluster of spheres, i.e., a size parameter of the target X(≡ 2πreq/λ) ∽ 50, where req is a volume equivalent radius of the target, and λ is the wavelength of incident wave.

scholarly journals The Search for Interstellar Components in Interplanetary Dust Particles

1996 ◽  
Vol 150 ◽  
pp. 275-282 ◽  
Author(s):  
John Bradley ◽  
Trevor Ireland
Keyword(s):  
Magnetic Field ◽  
Ionizing Radiation ◽  
Interstellar Medium ◽  
Solar Nebula ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Important Class ◽  
Galactic Magnetic Field ◽  
Interplanetary Dust Particles ◽  
Amorphous Silicate

AbstractAmorphous silicate grains known as GEMS have been found in chondritic porous interplanetary dust particles (IDPs) from comets. GEMS are composed of nanometer-sized FeNi metal and Fe-rich sulfide crystals embedded in silicate glass. The properties of GEMS appear to have been shaped primarily by exposure to ionizing radiation and, since the irradiation occurred prior to accretion of the cometary IDPs, GEMS may have formed either in the solar nebula or presolar interstellar environments. The sizes, shapes, structures, and compositions of GEMS correspond to those of interstellar “amorphous silicate” grains. Nanometer-sized superparamagnetic metal inclusions dispersed throughout GEMS provide a logical explanation for alignment of interstellar silicate grains in the galactic magnetic field. Irrespective of their origins, GEMS are an important class of submicrometersized chondritic objects. If they were formed in the solar nebula, then they are among the oldest known solar nebula solids. If they are presolar, then they are probably examples of the “amorphous silicate” grains which are ubiquitous throughout the interstellar medium.

scholarly journals Dust Destruction in the Interstellar Medium

1989 ◽  
Vol 135 ◽  
pp. 431-444 ◽  
Author(s):  
Christopher F. McKee
Keyword(s):  
Interstellar Medium ◽  
Refractory Material ◽  
Supernova Remnants ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Current Status ◽  
Interplanetary Dust Particles ◽  
Two Phase ◽  
Evolved Stars ◽  
Interstellar Grains

Grains are injected into the interstellar medium (ISM) from evolved stars and supernovae; in addition, supernova ejecta may condense onto pre-existing grains before becoming well-mixed with the interstellar gas. Once in the ISM, grains can grow by accretion, but are also subject to destruction by interstellar shocks. The current status of the theory of shock destruction of interstellar grains is reviewed briefly. Small grains are destroyed by thermal sputtering in fast, nonradiative shocks; large grains are destroyed by grain-grain collisions and eroded by nonthermal sputtering in radiative shocks. The dominant shocks in the ISM are from supernova remnants (SNRs), and the mass of grains destroyed is proportional to the energy of the SNR. In a multiphase ISM, these shocks destroy the grains at a rate proportional to the volume filling factor of the phase; since the density of the hot phase is too low for efficient grain destruction, most of the destruction occurs in the warm phase. Not all SNRs are effective at destroying grains, however: some are above the gas disk, and some —Type IPs in associations—are highly correlated in space and time. The galactic SN rate is observed to about 2.2 per century (van den Bergh, 1983), but the effective supernova rate for grain destruction is estimated to be only about 0.8 per century. As a result, the timescale for the destruction of a typical refractory grain in the ISM is inferred to be about 4 × 108 yr for either a two-phase or a three-phase ISM. Most of the refractory material in the ISM (other than carbon) is injected by supernovae, not evolved stars; the net injection timescale is estimated as about 1.5 × 109 yr. Comparison of the destruction and injection timescales indicates that the fraction of grains injected by stars which survive in the ISM is only about 20%. Most of the refractory material in interstellar grains must, therefore, have accreted onto the grains in the ISM. Nonetheless, a significant fraction of dust formed in stars survives in the ISM and may be detectable in meteorites and interplanetary dust particles.

scholarly journals Organics in meteorites - Solar or interstellar?

2008 ◽  
Vol 4 (S251) ◽  
pp. 293-298 ◽  
Author(s):  
Conel M. O'D. Alexander ◽  
George D. Cody ◽  
Marilyn Fogel ◽  
Hikaru Yabuta
Keyword(s):  
Interstellar Medium ◽  
Organic Material ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles

AbstractThe insoluble organic material (IOM) in primitive meteorites is related to the organic material in interplanetary dust particles and comets, and is probably related to the refractory organic material in the diffuse interstellar medium. If the IOM is representative of refractory ISM organics, models for how and from what it formed will have to be revised.

scholarly journals PAHs in Astronomy - A Review

2008 ◽  
Vol 4 (S251) ◽  
pp. 357-366 ◽  
Author(s):  
Farid Salama
Keyword(s):  
Aromatic Hydrocarbons ◽  
Observational Studies ◽  
Milky Way ◽  
Far Infrared ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
The Past ◽  
Polycyclic Aromatic ◽  
Solar System Bodies

AbstractCarbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of organic matter in space. Their contribution is invoked in a broad spectrum of astronomical observations that range from the ultraviolet to the far-infrared and cover a wide variety of objects and environments from meteorites and interplanetary dust particles to outer Solar System bodies to the interstellar medium in the local Milky Way and in other galaxies. Extensive efforts have been devoted in the past two decades to experimental, theoretical, and observational studies of PAHs. A brief review is given here of the evidence obtained so far for the contribution of PAHs to the phenomena aforementioned. An attempt is made to distinguish the cases where solid evidence is available from cases where reasonable assumptions can be made to the cases where the presence - or the absence - of PAHs is purely speculative at this point.

IDENTIFICATION AND ANALYSIS OF INTERPLANETARY DUST PARTICLES FILTERED FROM ANTARCTIC AIR

2018 ◽  
Author(s):  
Katherine Burgess ◽  
◽  
David Bour ◽  
Rhonda M. Stroud ◽  
Anais Bardyn ◽  
...  
Keyword(s):  
Interplanetary Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles

scholarly journals On Two Mechanisms of X-Ray Generation in Comets

1985 ◽  
Vol 85 ◽  
pp. 365-368
Author(s):  
S. Ibadov
Keyword(s):  
High Temperature ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Interplanetary Dust Particles ◽  
Temperature Plasma ◽  
X Ray ◽  
Plasma Generation ◽  
High Temperature Plasma

AbstractThe intensity of solar X-radiation scattered by a comet is calculated and compared to the proper X-radiation of the comet due to impacts of cometary and interplanetary dust particles. Detection of X-radiation of dusty comets at small heliocentric distances (R ≤ 1 a.u.) is found to be an indicator of high-temperature plasma generation as result of grain collisions.

Sign in / Sign up

Export Citation Format

Share Document