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Interstellar dust trajectory simulations and the role of the heliosphere

Interstellar dust is at the base of the formation of stars and planetary systems and plays an important role in the chemistry of the interstellar medium. To study it, we can use astronomical observations (e.g. extinction and polarisation of starlight, infrared emission of the dust), but we can also probe the interstellar dust particles from our immediate interstellar neighbourhood: the Local Interstellar Cloud (LIC). Because of the relative motion between the Sun and the LIC (ca. 26 km/s), we can investigate these interstellar dust particles within the solar system using dust detectors on spacecraft like Ulysses, Galileo, Helios and Cassini, or we can catch them at relatively low relative velocities of only a few km/s, and return them to Earth for a detailed study in the laboratory (e.g. the Stardust mission).

The trajectories of these particles while passing through the solar system are governed by several forces like solar gravity, solar radiation pressure force and Lorentz force due to the motion of the (charged) dust particles through the Interplanetary Magnetic Field (IMF). Computer simulations of ISD trajectories shed light on the variable ISD particle fluxes and directions, as it changes throughout the solar cycle. With computer simulations, we gain insight in the flow patterns of interstellar dust in the solar system, investigate how much arrives at the Earth, the asteroid belt, Jupiter or Saturn, and we can make predictions for the fluxes to be measured by several space missions.

Simulations for the 16 years of Ulysses dust measurements indicated that the observed shift in dust flow direction in 2005/2006, may be explained if the larger interstellar dust particles have a lower bulk density than anticipated (cf. paper on the Ulysses measurements and simulations), but this remains to be proven. Also the Stardust mission yielded analysis results that indicated lower bulk densities for the micron-sized interstellar dust candidates.

So far, the inner heliosphere’s magnetic field was taken into account; the outer heliosphere is the next step to come and is subject of the ERC Starting Grant ASTRODUST.

The main goal of the research is to understand the existing datasets of interstellar dust, complemented by future missions (e.g. Destiny+), to constrain the dust particle properties (composition, morphology, etc.), and to provide an extra constraint for models of the outer heliosphere.

Current Mission involvement

Past topics:

  • Joint Europa Mission (JEM) proposal for the ESA M5 call for medium-class missions. The goal of this mission is to explore the habitability of the Jovian moon Europa in a joint ESA-NASA effort.
  • S2D2 Proposal for ESA science themes for L-class missions: a mission concept consisting of two spacecraft to map the solar system in dust: one in-situ spacecraft for the dust flux and chemical composition in order to link the solar system dust and their parent bodies, and one infrared telescope out-of-the ecliptic plane for a birds-eye view on the solar system debris disk. PI: Ralf Srama, Univ. Stuttgart. (2013)
  • Support for the development of the ESA IMEX model (2013)
  • Characterization and mitigation of optical path disturbances of the Darwin mission (2007-2008)
  • History of science: the life and work of Sir Hermann Bondi (2006)
  • Orbit calculations in L2 for the GAIA mission using FEEPS (2002)