When the Sun shakes

Research scientists studying the Sun have found that the Sun is shaking – vibrating like a colossal musical instrument. Scientists are learning from our Sun and will be able to measure the interiors of other stars.

When the Sun shakes

Although we can’t see it without special equipment, the Sun is shaking. Bubbling motion just under the visible surface is constantly feeding in energy, and the Sun responds by vibrating like a colossal musical instrument. The ‘notes’ of this stellar music are fascinating to astronomers. They are produced by sound waves which have travelled deep inside the Sun, and their frequencies (the ‘pitches’ of the notes) depend on the conditions they’ve encountered on the way: for example, the density and temperature of the material inside the Sun. Studying these sound waves essentially allows an ‘ultrasound scan’ of our nearest star.

Turning these ideas into scientific reality is extremely difficult. The shaking of the Sun’s surface is very small. It moves to and fro at a couple of meters per second (a slow walking pace), and takes about five minutes to go through a vibrational cycle. Detecting this movement takes specially designed instruments: spectrometers that analyse the spectrum of sunlight with fantastic precision, sensing for the tiny shifts in light frequency (Doppler shift) as the Sun’s surface rises towards, or recedes from, the Earth.

There is a cycle of magnetic activity (and we don’t fully understand it yet) that causes the Sun to produce an unusually high number of ‘sunspots’ every 11 years or so. For this and other reasons, scientists would really like to observe the Sun’s vibrations all the time, and over many years.

One way of doing this is to have a number of robotic spectrometers in different sunny locations around the world, so that when the Sun sets on one instrument it has already risen on another. The Birmingham Solar Oscillations Network (BiSON) is just such a network of spectrometers. There are instruments in the Americas, Australia, Tenerife and South Africa. The BiSON team designed and built them, and they’re kept running with support from local collaborators, and by field site visits. The data are returned to the BiSON base in Birmingham via the Internet, and the remote link also lets the team monitor the performance of the instruments and upgrade some of the software.

Results from BiSON have been very valuable in helping astronomers to understand the Sun. The spectrum of its deepest vibrations was first detected by BiSON. Now astronomers are learning how to measure the interiors of other stars, with the Sun as an important reference point for this new work.

 

Source: http://www.sunearthplan.net/1/12/When-the-Sun-shakes

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Tags: Research, sunlight, sunspots, vibration