The recent research domain of asteroseismology refers to the study of the internal structure of pulsating stars through the interpretation of their frequency spectra. Asteroseismologists make great use of the oscillations to probe the stellar interior, which is not directly observable. The basic principles of asteroseismology are very much alike those developed by earth seismologists.
No part of the Universe is more difficult to observe directly than the interior of the stars. The reason why stellar interiors can be probed from oscillations is that different oscillation modes penetrate to different depths inside the star. Asteroseismology is the only available method so far to derive the internal structure of the stars with high precision.
No part of the Universe is more difficult to observe directly than the interior of the stars. The reason why stellar interiors can be probed from oscillations is that different oscillation modes penetrate to different depths inside the star. Asteroseismology is the only available method so far to derive the internal structure of the stars with high precision.
Credit:
University of Leuven
Astrophysicists at the Institute of Astronomy of the University of Leuven play a central role in the interpretation of oscillation data of B-type stars. These are massive stars, with masses between 3 and 30 times the mass of the Sun. Stars heavier than roughly 9 solar masses will explode as a supernova at the end of their life. Thanks to such explosions, the interstellar medium is enriched with products of the nuclear burning in the stellar core, i.e. with chemical elements heavier than hydrogen and helium.
Oscillations can be excited in stars when thermal energy is converted into kinetic energy of pulsation. Similarly as for any heat engine, this proces is effective if heat is absorbed in the high temperature phase of oscillation and emitted when the temperature is low. The main mechanism for stars is the net conversion of radiation energy into pulsational energy in the surface layers of some classes of stars. The resulting oscillations are usually studied under the assumption that they are small, and that the star is isolated and spherically symmetric.
Astrophysicists at the Institute of Astronomy of the University of Leuven play a central role in the interpretation of oscillation data of B-type stars. These are massive stars, with masses between 3 and 30 times the mass of the Sun. Stars heavier than roughly 9 solar masses will explode as a supernova at the end of their life. Thanks to such explosions, the interstellar medium is enriched with products of the nuclear burning in the stellar core, i.e. with chemical elements heavier than hydrogen and helium.
Oscillations can be excited in stars when thermal energy is converted into kinetic energy of pulsation. Similarly as for any heat engine, this proces is effective if heat is absorbed in the high temperature phase of oscillation and emitted when the temperature is low. The main mechanism for stars is the net conversion of radiation energy into pulsational energy in the surface layers of some classes of stars. The resulting oscillations are usually studied under the assumption that they are small, and that the star is isolated and spherically symmetric.
Credit: University of Leuven
At the Institute of Astronomy, several basic properties of stellar oscillations have been developed and clarified, and we are interested in the behaviour of oscillating stars when the above assumptions are relaxed. In particular, the Institute develops asymptotic representations of stellar oscillations, which are very useful for gaining insight into the deep layers of stars, and study the influence of stellar rotation and nonlinear effects on the oscillations. Furthermore, as multiple stars are very common, they investigate stellar tides and the effects of a tidal force on oscillating stars.
For a more detailed basic text on asteroseismology of massive stars (including references), click here.
To retrieve the discriminant code developed at the IvS to identify non-radial oscillation modes from line-profile variations, click here
Source: University of Leuven
For a more detailed basic text on asteroseismology of massive stars (including references), click here.
To retrieve the discriminant code developed at the IvS to identify non-radial oscillation modes from line-profile variations, click here
Source: University of Leuven
0 comments:
Post a Comment