The Polarization of Starlight by Interstellar Dust Particles in a Galactic Magnetic Field

1949 ◽  
Vol 75 (10) ◽  
pp. 1605-1605 ◽  
Author(s):  
Leverett Davis ◽  
Jesse L. Greenstein
1996 ◽  
Vol 150 ◽  
pp. 275-282 ◽  
Author(s):  
John Bradley ◽  
Trevor Ireland

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.


2008 ◽  
Vol 4 (S259) ◽  
pp. 613-622
Author(s):  
Tim M. Gledhill

AbstractSome of the earliest polarimetric measurements made in astronomy were concerned with the polarization of the interstellar medium resulting from dust grains aligned in the Galactic magnetic field. More than 50 years later, polarimetry continues to be an important diagnostic of field structure on size scales ranging from planetary to galactic. The use of both linear and circular polarimetry at optical and infrared wavelengths can provide additional insights into the nature of dust particles, their alignment in magnetic fields and the field topology. Given the science benefits that polarimetry offers it is perhaps surprising that the continued existence of polarimetric facilities on current and next generation large telescopes needs to be ensured.


2021 ◽  
Author(s):  
Silvan Hunziker ◽  
Veerle Sterken ◽  
Peter Strub ◽  
Harald Krüger ◽  
Aigen Li

<p>Interstellar Probe is an ambitious mission concept, to reach interstellar space (up to 1000 AU). Its launch date is between 2030 and 2042 and its goals cover different fields of science from planetary science, heliophysics (heliosphere), to astronomy. One main goal is to significantly expand our knowledge about our heliosphere, the interstellar medium, and how both interact with each other. Among many other instruments, the space probe is planned to carry a dust mass spectrometer that will be able to capture dust particles and measure their composition. This will be especially useful for measuring the interstellar dust of the local interstellar medium that continuously streams through the solar system and has been directly detected for the first time with the Ulysses spacecraft in the 1990s. The mass distributions from such in situ dust detections in the solar system so far have shown a significant discrepancy compared to the results from astronomical observations. We performed a series of simulations of the interstellar dust trajectories and distribution inside the solar system and use them to predict the ability of the Interstellar Probe to measure interstellar dust particles and how this ability is affected by different spacecraft trajectories and dust detector setups. We also discuss how the filtering of small dust particles at the boundary regions of the heliosphere affects our predictions and indicate how in situ dust measurements can be used to constrain the filtering process. In general, most of the dust particles can be measured if the spacecraft moves towards the nose of the heliosphere. However, we also find a significant correlation between the presence of small dust particles (<0.3 microns) in the inner solar system and the phase of the solar cycle which is caused by the filtering effect of the solar magnetic field via the Lorentz force. Inside the heliosphere, the interstellar Probe may be able to detect and analyze up to 1 interstellar dust particle per day for particle sizes >0.1 micron and many more of the smaller particles, depending on the state of the solar magnetic field and the dust filtering at the boundary of the heliosphere. Outside the heliosphere, the absence of dust filtering should increase the detection rate of small particles (<0.1 microns) to more than 10 per day.</p>


1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.


1967 ◽  
Vol 31 ◽  
pp. 355-356
Author(s):  
R. D. Davies

Observations at various frequencies between 136 and 1400 MHz indicate a considerable amount of structure in the galactic disk. This result appears consistent both with measured polarization percentages and with considerations of the strength of the galactic magnetic field.


1977 ◽  
Vol 121 (4) ◽  
pp. 679 ◽  
Author(s):  
T.A.T. Spoelstra

2021 ◽  
Vol 503 (4) ◽  
pp. 5274-5290
Author(s):  
A K Sen ◽  
V B Il’in ◽  
M S Prokopjeva ◽  
R Gupta

ABSTRACT We present the results of our BVR-band photometric and R-band polarimetric observations of ∼40 stars in the periphery of the dark cloud CB54. From different photometric data, we estimate E(B − V) and E(J − H). After involving data from other sources, we discuss the extinction variations towards CB54. We reveal two main dust layers: a foreground, E(B − V) ≈ 0.1 mag, at ∼200 pc and an extended layer, $E(B-V) \gtrsim 0.3$ mag, at ∼1.5 kpc. CB54 belongs to the latter. Based on these results, we consider the reason for the random polarization map that we have observed for CB54. We find that the foreground is characterized by low polarization ($P \lesssim 0.5$ per cent) and a magnetic field parallel to the Galactic plane. The extended layer shows high polarization (P up to 5–7 per cent). We suggest that the field in this layer is nearly perpendicular to the Galactic plane and both layers are essentially inhomogeneous. This allows us to explain the randomness of polarization vectors around CB54 generally. The data – primarily observed by us in this work for CB54, by A. K. Sen and colleagues in previous works for three dark clouds CB3, CB25 and CB39, and by other authors for a region including the B1 cloud – are analysed to explore any correlation between polarization, the near-infrared, E(J − H), and optical, E(B − V), excesses, and the distance to the background stars. If polarization and extinction are caused by the same set of dust particles, we should expect good correlations. However, we find that, for all the clouds, the correlations are not strong.


2015 ◽  
Vol 112 (24) ◽  
pp. 7438-7443 ◽  
Author(s):  
Tetsuya Hama ◽  
Hirokazu Ueta ◽  
Akira Kouchi ◽  
Naoki Watanabe

Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle’s ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1–1.5) despite the large intrinsic H/D KIE of tunneling (≳100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system.


2018 ◽  
Vol 867 (2) ◽  
pp. 139 ◽  
Author(s):  
G. L. Verschuur ◽  
J. T. Schmelz ◽  
M. Asgari-Targhi

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