SIX observatories around the globe turned to face the Sun early this month in search of some good vibrations. The Global Oscillation Network Group (GONG) will allow astronomers to watch the Sun as it vibrates in space, giving them clues to the internal workings of the star and perhaps allowing them to predict the development of sunspots on the far side.
鈥淭he Sun will never set on the GONG,鈥� says John Leibacher, director of the project at the US government鈥檚 National Optical Astronomy Observatories. The team has picked sites for the telescopes in California, Spain, India, Australia, Hawaii and Chile 鈥� so that at least one should always have blue skies and a clear view of the Sun.
As pressure waves well up from the Sun鈥檚 core, the surface vibrates as if it is a ringing bell. The GONG observatories will track these subtle pulsations of the surface by detecting variations in the frequency of light reaching Earth. Helioseismologists such as Leibacher expect to discover a wide range of details about the Sun, including the temperature and molecular weight of the ionised gas through which the waves travel.
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The vibrations could even alert the team to sunspots forming on the side of the Sun facing away from Earth. Sunspots act like 鈥渟inks鈥�, absorbing energy from pressure waves. It may be that this effect can be predicted from measurements taken on the side of the Sun facing Earth. 鈥淚t鈥檚 like what happens when there鈥檚 an earthquake in China. You don鈥檛 have to be in China to know that it has happened,鈥� Leibacher says. 鈥淵ou can tell from the seismic waves.鈥�
Initial plans are for the GONG to watch the Sun for 1000 days. Beyond this deadline, the GONG鈥檚 fate is uncertain. In May or June, Leibacher and his collaborators from 20 nations will publish their initial findings. 鈥淲hen we start getting the data, we鈥檒l finally know what goes on inside a star,鈥� says Leibacher.