2D RADIATIVE TRANSFER IN ASTROPHYSICAL DUSTY ENVIRONMENTS

I have developed a new general-purpose deterministic 2D radiative transfer code for astrophysical dusty environments named LELUYA (www.leluya.org). It can provide the solution to an arbitrary axially symmetric multi-grain dust distribution around an arbitrary heating source. By employing a new numerical method, the implemented algorithm automatically traces the dust density and optical depth gradients, creating the optimal unstructured triangular grid. The radiative transfer equation includes dust scattering, absorption and emission. Unique to LELUYA is also its ability to self-consistently reshape the sublimation/condensation dust cavity around the source to accommodate for the anisotropic diffuse radiation. LELUYAs capabilities are demonstrated in the study of the asymptotic giant branch (AGB) star IRC+10011. The stellar winds emanating from AGB stars are mostly spherically symmetric, but they evolve into largely asymmetric planetary nebulae during later evolutionary phases. The initiation of this symmetry breaking process is still unexplained. IRC+10011 represents a rare example of a clearly visible asymmetry in high-resolution near-infrared images of the circumstellar dusty AGB wind. LELUYA shows that this asymmetry is produced by two bipolar cones with 1/r0.5 density profile, imbedded in the standard 1/r2 dusty wind profile. The cones are still breaking though the 1/r2 wind, suggesting they are driven by bipolar jets. They are about 200 years old, thus a very recent episode in the final phase of AGB evolution before turning into a proto-planetary nebula, where the jets finally break out from the confining spherical wind. IRC+10011 provides the earliest example of this symmetry breaking thus far

The challenges in hypervelocity microphysics research on meteoroid impacts into the atmosphere

Meteor science contributes greatly to the study of the Solar System and the Earth's atmosphere. However, despite its importance and very long history, meteor science still has a lot to explore in the domain of meteor plasma microphysics and the meteor-ionosphere interaction. Meteors are actually a difficult target for high-resolution observations, which leads to the need for more ambitious interdisciplinary observational setups and campaigns. We describe some recent developments in the physics of meteor flight and microphysics of meteor plasma and argue that meteor science should be fully integrated into the science cases of large astronomical facilities.Peer reviewe

Educational asymmetries in the making: Science Fair Competitions as Proxies of the Economic Development

Croatia does not score well in the human development index, rate of employment, or development of the high tech sector - to mention only a few indicators that hinder good prospects for improvement. Also, Croatian high school students are at the bottom of European rankings on performance in science and mathematics and their interest in career in science is declining. Croatia needs more educated people, especially in the area of science and technology, and this can be achieved only if the youth become interested in science at an early age. Thus, science fair competitions are of an utmost importance for development of Croatia. This paper aims at investigating a relation of the Croatian counties' development index and their students' participation rates in the science fair competitions. This is done by including two development indexes in search for the relation with the counties' participation rates in biology, chemistry, physics and mathematics competition, and with a reference to a previous research on astronomy competition. As is revealed, there is a growing trend of interconnection of the development index and participation rates at science competitions in all disciplines.Comment: 25 pages, published in Sociologija i prostor, 2010, Vol.48(1), http://hrcak.srce.hr/index.php?show=clanak&id_clanak_jezik=8428

Outflows From Evolved Stars: The Rapidly Changing Fingers Of CRL 618

Our ultimate goal is to probe the nature of the collimator of the outflows in the pre-planetary nebula CRL 618. CRL 618 is uniquely suited for this purpose owing to its multiple, bright, and carefully studied finger-shaped outflows east and west of its nucleus. We compare new Hubble Space Telescope images to images in the same filters observed as much as 11 yr ago to uncover large proper motions and surface brightness changes in its multiple finger-shaped outflows. The expansion age of the ensemble of fingers is close to 100 yr. We find strong brightness variations at the fingertips during the past decade. Deep IR images reveal a multiple ring-like structure of the surrounding medium into which the outflows propagate and interact. Tightly constrained three-dimensional hydrodynamic models link the properties of the fingers to their possible formation histories. We incorporate previously published complementary information to discern whether each of the fingers of CRL 618 are the results of steady, collimated outflows or a brief ejection event that launched a set of bullets about a century ago. Finally, we argue on various physical grounds that fingers of CRL 618 are likely to be the result of a spray of clumps ejected at the nucleus of CRL 618 since any mechanism that form a sustained set of unaligned jets is unprecedented.HST GO 11580NASA through Space Telescope Science Institute GO11580NASA NAS5-26555Boeing ScholarshipOffice of Undergraduate Academic Affairs at the University of WashingtonSpanish MICINN CSD2009-00038NASA Office of Space Science NAG5-7584Astronom

The Illumination and Growth of CRL 2688: An Analysis of New & Archival HST Observations

We present four-color images of CRL 2688 obtained in 2009 using the Wide-Field Camera 3 on HST. The F606W image is compared with archival images in very similar filters to monitor the proper motions of nebular structure. We find that the bright N-S lobes have expanded uniformly by 2.5% and that the ensemble of rings has translated radially by 0.07 in 6.65 y. The rings were ejected every 100y for ~4 millennia until the lobes formed 250y ago. Starlight scattered from the edges of the dark E-W dust lane is coincident with extant H2 images and leading tips of eight pairs of CO outflows. We interpret this as evidence that fingers lie within geometrically opposite cones of opening angles {\approx} 30{\circ} like those in CRL618. By combining our results of the rings with 12CO absorption from the extended AGB wind we ascertain that the rings were ejected at ~18 km s-1 with very little variation and that the distance to CRL2688, v_{exp}$/${\dot\theta}_exp$, is 300 - 350 pc. Our 2009 imaging program included filters that span 0.6 to 1.6{\mu}m. We constructed a two-dimensional dust scattering model of stellar radiation through CRL2688 that successfully reproduces the details of the nebular geometry, its integrated spectral energy distribution, and nearly all of its color variations. The model implies that the optical opacity of the lobes >~ 1, the dust particle density in the rings decreases as radius^{-3} and that the mass and momentum of the AGB winds and their rings have increased over time.Comment: (51 pages, 6 figures; accepted by ApJ

Meteor Observations as Big Data Citizen Science

Meteor science represents an excellent example of the citizen science project, where progress in the field has been largely determined by amateur observations. Over the last couple of decades technological advancements in observational techniques have yielded drastic improvements in the quality, quantity and diversity of meteor data, while even more ambitious instruments are about to become operational. This empowers meteor science to boost its experimental and theoretical horizons and seek more advanced scientific goals. We review some of the developments that push meteor science into the Big Data era that requires more complex methodological approaches through interdisciplinary collaborations with other branches of physics and computer science. We argue that meteor science should become an integral part of large surveys in astronomy, aeronomy and space physics, and tackle the complexity of micro-physics of meteor plasma and its interaction with the atmosphere. The recent increased interest in meteor science triggered by the Chelyabinsk fireball helps in building the case for technologically and logistically more ambitious meteor projects. This requires developing new methodological approaches in meteor research, with Big Data science and close collaboration between citizen science, geoscience and astronomy as critical elements. We discuss possibilities for improvements and promote an opportunity for collaboration in meteor science within the currently established BigSkyEart