Search results for "Cosmic dust"
showing 5 items of 5 documents
SHARDS: A global view of the star formation activity at z~0.84 and z~1.23
2015
et al.
An idealized mechanism for the orbital migration of protoplanets
1993
We report here how the action of radiation forces on small solid particles in a circumstellar disc could induce a suitable mechanism for orbital migration of protoplanets. The ratio of radiation-to-gravitational forces acting on a particle depends on its physical and chemical properties. As a consequence of this fact, we show that different particles following the same trajectory would move with different velocities. Sufficiently large bodies, insensitive to radiation forces, would accrete dust particles that are moving more slowly, thus spiralling towards the central star and transporting mass and angular momentum from the outer to the inner parts of the circumstellar disc. In the case of …
Radiation forces and the formation of planetary systems
1990
We briefly support on some new results about the influence of the rotation and finite size of a stellar radiation source on dust particle orbits, emphasizing the possibility of stable orbits, in the equatorial plane, for dust sizes near the radiation pressure limit.
AE Aurigae: First detection of non-thermal X-ray emission from a bow shock produced by a runaway star
2012
Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace due to the encounter of two massive binary systems and now is passing through the dense nebula IC 405…
Subsurface chemistry of mantles of interstellar dust grains in dark molecular cores
2010
Context. The abundances of many observed compounds in interstellar molecular clouds still lack an explanation, despite extensive research that includes both gas and solid (dust-grain surface) phase reactions. Aims. We aim to qualitatively prove the idea that a hydrogen-poor subsurface chemistry on interstellar grains is responsible for at least some of these chemical "anomalies". This chemistry develops in the icy mantles when photodissociation reactions in the mantle release free hydrogen, which escapes the mantle via diffusion. This results in serious alterations of the chemical composition of the mantle because pores in the mantle provide surfaces for reactions in the new, hydrogen-poor …