Stars vibrate according to many different pulsation modes in much the same way that musical instruments emit a variety of sounds.
 Listening to an air on the guitar does not leave any doubt as to the nature of the instrument, and an experienced musician can even deduce the cords' material and tension.
Similarly, stellar pulsation modes are characteristic of global stellar properties and of the internal physical conditions.
 Analyzing these modes is thus a way of probing stellar interiors to infer stellar chemical composition, rotation profiles and internal physical properties such as temperatures and densities.
Asteroseismology is the science which studies the vibration modes of a star.
Each of these modes can be mathematically represented by a spherical harmonic of degree l and azimuthal order m. Some examples are presented here below with a color scheme in which blue (red) indicates contracting (expanding) material.
The pulsation amplitudes are highly exaggerated.

When applied to the Sun, this science is called helioseismology and has been ongoing for a few decades by now.
The solar surface helium abundance was derived very accurately for the first time, which has definitely shown the importance of microscopic diffusion in the solar structure.
Helioseismology analyses have also unveiled the solar internal rotational profile, the precise extent of the convective envelope and the location of the helium ionization zone.
Despite enormous technical challenges, it was thus tempting to apply similar analyses to stars.
From the ground this was only possible for stars close to the Sun such as α Centauri, Procyon, β Virginis... The goal is to detect extremely small light variations (down to 1 ppm) and to extract the frequencies responsible for these brightness fluctuations.
This produces a frequency spectrum typical of the star under scrutiny.
Oscillation periods vary from a few minutes to several hours depending of the type of star and its evolutionary state.
To reach such performances, long observing times devoid of day/night alternations are required.
Space is thus the ideal asteroseismic laboratory.
By revealing their microvariability, measuring their oscillations at the ppm level, CoRoT has provided a new vision of stars, never reached before by any ground-based observation.

At the beginning of the mission, two out of four CCDs were assigned to asteroseismic observations of bright stars (apparent magnitude 6 to 9) in the so-called seismo field while the other CCDs were reserved for exoplanet hunting in the so-called exo field.
Albeit with a lower signal to noise ratio, interesting science on stars was also obtained from the exoplanets channel data, where the probe records several thousands of light curves from every observed field.
Stellar activity, rotation periods, star spot evolution, star–planet interactions, multiple star systems are nice extras in addition to the main asteroseismic program.
This exo field also turned out to be of incalculable richness in asteroseismic discoveries.
During the first six years of its mission, CoRoT has observed about 150 bright stars in the seismo field and more than 150 000 weak stars in the exo field.
The figure shows where most of them are located in the Hertzsprung–Russell diagram together with some others observed from the ground.

Discoveries were numerous.
Let us cite the first detection of solar-like oscillations in stars other than the Sun, the first detection of non-radial oscillations in red giant stars, the detection of solar-like oscillations in massive stars · , the discovery of hundreds of frequencies in δ Scuti stars, the spectacular time evolution of the frequency spectrum of a Be (emission lines B) star during an outburst, the first detection of a deviation from a constant period spacing in gravity modes in an SPB (Slowly Pulsating B) star.
Interpreting those results opened new horizons in our vision of stars and galaxies.
In October 2009 the CoRoT mission was the subject of a special issue of Astronomy and Astrophysics, dedicated to the early results of the probe.
Below
Stars vibrate according to many different pulsation modes in much the same way that musical instruments emit a variety of sounds.  Listening to an air on the guitar does not leave any doubt as to the nature of the instrument, and an experienced musician can even deduce the cords' material and tension. Similarly, stellar pulsation modes are characteristic of global stellar properties and of the internal physical conditions.  Analyzing these modes is thus a way of probing stellar interiors to infer stellar chemical composition, rotation profiles and internal physical properties such as temperatures and densities. Asteroseismology is the science which studies the vibration modes of a star. Each of these modes can be mathematically represented by a spherical harmonic of degree l and azimuthal order m. Some examples are presented here below with a color scheme in which blue (red) indicates contracting (expanding) material. The pulsation amplitudes are highly exaggerated.
When applied to the Sun, this science is called helioseismology and has been ongoing for a few decades by now. The solar surface helium abundance was derived very accurately for the first time, which has definitely shown the importance of microscopic diffusion in the solar structure. Helioseismology analyses have also unveiled the solar internal rotational profile, the precise extent of the convective envelope and the location of the helium ionization zone. Despite enormous technical challenges, it was thus tempting to apply similar analyses to stars. From the ground this was only possible for stars close to the Sun such as α Centauri, Procyon, β Virginis... The goal is to detect extremely small light variations (down to 1 ppm) and to extract the frequencies responsible for these brightness fluctuations. This produces a frequency spectrum typical of the star under scrutiny. Oscillation periods vary from a few minutes to several hours depending of the type of star and its evolutionary state. To reach such performances, long observing times devoid of day/night alternations are required. Space is thus the ideal asteroseismic laboratory. By revealing their microvariability, measuring their oscillations at the ppm level, CoRoT has provided a new vision of stars, never reached before by any ground-based observation.
At the beginning of the mission, two out of four CCDs were assigned to asteroseismic observations of bright stars (apparent magnitude 6 to 9) in the so-called seismo field while the other CCDs were reserved for exoplanet hunting in the so-called exo field. Albeit with a lower signal to noise ratio, interesting science on stars was also obtained from the exoplanets channel data, where the probe records several thousands of light curves from every observed field. Stellar activity, rotation periods, star spot evolution, star–planet interactions, multiple star systems are nice extras in addition to the main asteroseismic program. This exo field also turned out to be of incalculable richness in asteroseismic discoveries. During the first six years of its mission, CoRoT has observed about 150 bright stars in the seismo field and more than 150 000 weak stars in the exo field. The figure shows where most of them are located in the Hertzsprung–Russell diagram together with some others observed from the ground.
Discoveries were numerous. Let us cite the first detection of solar-like oscillations in stars other than the Sun, the first detection of non-radial oscillations in red giant stars, the detection of solar-like oscillations in massive stars · , the discovery of hundreds of frequencies in δ Scuti stars, the spectacular time evolution of the frequency spectrum of a Be (emission lines B) star during an outburst, the first detection of a deviation from a constant period spacing in gravity modes in an SPB (Slowly Pulsating B) star. Interpreting those results opened new horizons in our vision of stars and galaxies. In October 2009 the CoRoT mission was the subject of a special issue of Astronomy and Astrophysics, dedicated to the early results of the probe. Below
CoRoT