Extragalactic research in Oulu

We use data from ground-based and space telescopes, including modern instruments at European Southern Observatory (ESO). We do dynamical modeling of galaxies using both N-body codes developed in our group (Salo & Laurikainen 2000a,b), and with other codes in collaboration with other researchers. We have developed both 2D-decomposition structural decomposition methdods (see BDBAR, Laurikainen et al. 2005), and methods for estimating the gravitational field of the galaxies from near-IR images (NIRQB, Laurikainen and Salo 2002).
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Galactic Rings and Thick Disks

Many of the most spectacular galaxies are spiral galaxies. Those galaxies have a disc with bright spiral arms, where usually enhanced star formation occurs.
Spiral galaxies often host a bar. A bar is an elongated structure made of stars. Bars break the symmetry of the galaxies. In a symmetric galaxy, orbits would be close to circular, but in a barred galaxy the orbits of stars and gas clouds are perturbed.
Gas clouds perturbed by bars are moved to certain orbits that are said to be resonant with the bar. Gas accumulates there. When gas density becomes high enough clouds collapse under their own gravity and star formation begins. This is the origin of the so-called resonance rings.
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Solar System Research

One focus of research are small particles found in the environment of the planets of the solar system (circumplanetary dust). These particles are usually smaller than one millimeter, often only a thousandth or a millionth of millimeter in size. Such particles are widely distributed in the Solar system, often forming ring systems around the gas giants. The grains can be created in a number of different processes. What makes them interesting to study is that they bear information from their points of origin, like the surfaces or even the interiors of the moons of the giant planets. Also, because their motion is affected by the environment of the giant planets, like the presence of magnetic fields or ions and neutral gas, we can learn about this environment from analysing the paths that these particles have taken. Another motivation for the study of dust around the planets is spacecraft hazard: Impacts of larger particles tend to degrade the hardware of spacecraft and in extreme cases may lead to fatal damage.
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Interacting binary stars

The focus of our research to date has been on the investigation of semi-detached binary stars, principally the study of cataclysmic variables. Cataclysmic Variables (CVs) are close interacting binaries that contain a white dwarf accreting material transferred from a companion, usually a late main-sequence star. Unless the white dwarf has an extremely strong magnetic field, the transferred mass forms an accretion disk around this star. CVs are very active photometrically, exhibiting variability on time scales from seconds to centuries. An important reason to investigate the CVs is that they provide an unparalleled way to study two fundamental astrophysical processes: binary star evolution and nearly all aspects of the accretion of gas onto compact objects.
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