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Listening To Other Stars

Listening To Other Stars

When scientists realised that observing and analysing oscillations in the Sun could provide information about its interior, it was only a matter of time before Helioseismology was put to work on other stars.

The techniques used in Solar and Stellar Seismology are exactly the same, but applying them to other stars presents a greater challenge than the Sun because they are much farther away.

This means that less light reaches us from them, making it more difficult to observe the slight changes in their oscillations that cause fluctuations in the brightness we can see.

These changes are not easy to observe in the Sun either, although it helps that we can focus its light onto a point (like a star) and, because the Sun is close, we can obtain high resolution images of its sphere and see how waves spread from one zone to another.

The jump to Asteroseismology

William Chaplin, of the University of Birmingham spoke at the "4th International HELAS Conference" about how Stellar Seismology is demanding new instruments to observe these effects in stars, which need to be mounted on satellites to take continuous, high quality readings from above the Earth's atmosphere.

Despite advances in technology, he said, ""it is still not possible to obtain a high resolution image of a star's disc. This means that we can only see waves that are propagated across the whole of the star (in contrast to what we can see on the Sun)."

Until recently the mass, radio signature and age of stars were determined using non-seismological techniques and the results were very inaccurate. Seismology is delivering great improvements. According to Chaplin, "it is now becoming possible to obtain images of the surface of large relatively near stars.

In 20 or 30 years the technology will make it possible to observe these stars in as much detail as we can observe our Sun today. Whether this will happen during my working life is unclear."

Extrasolar planets

"One method for detecting extrasolar planets, used on the CoRoT and Kepler missions, both dedicated also to the Asteroseismology observations, is calculating the extent to which a star's light dims when a planet transits in front of it. (Credit: Image courtesy of Instituto de Astrofisica de Canarias)"

Source: Instituto de Astrofisica de Canarias

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