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Headlines Published on 2 July 2009

Title European researchers make advances in solar eclipse studies

European researchers have succeeded in linking solar observations from satellites with ground-based observations. They used state-of-the-art image processing tools to reveal spatial details, effectively showing the structure of the coronal magnetic field. The findings are published in a review of the journal Nature.

A composite image of the sunspot-minimum 2008 eclipse corona and prominences, put together from 16 individual frames of a variety of exposure times made at Akademgorodok, Siberia © W. Carlos and J.M.P.
A composite image of the sunspot-minimum 2008 eclipse corona and prominences, put together from 16 individual frames of a variety of exposure times made at Akademgorodok, Siberia
© W. Carlos and J.M.P.

The researchers from the Brno University of Technology (Czech Republic), ASTELCO Systems GmbH (Germany) and the Bratislava-based Slovak Academy of Sciences went one step further in the study of eclipses by making ground-based eclipse observations touching on spatial, temporal and spectral-resolution domains which cannot be reached from space.

According to Professor Jay M. Pasachoff of Williams College in the US, scientists have been able to make amazing discoveries by observing the Sun during total eclipses. For instance, they determined the high temperature of the corona, which is the outermost region of the Sun's atmosphere, visible as a white halo during an eclipse.

A total solar eclipse event is the result of the Moon coming directly between the Earth and Sun. Professor Pasachoff notes such eclipses happen when the Moon and Sun are sufficiently near the nodes (i.e. the crossing points of the Moon's apparent path in the sky and the ecliptic (the great circle representing the apparent annual path of the Sun).

Professor Pasachoff explains that while telescopes on satellites can handle research about the corona, some aspects are 'uniquely able to be studied from Earth at total solar eclipses'. According to the astronomer, mountain-top coronagraphs can monitor the low corona but the images are not very detailed.

Spacecraft instruments, while developed for specific purposes, are 'locked into their configurations many years in advance of their use', added Professor Pasachoff. But quite the opposite is true for eclipse expeditions; they can use advanced equipment as well as the latest theoretical ideas to frame observations, he remarked.

Other advantages are that eclipse expeditions can take larger solar telescopes than those in space, and they can burn fewer holes in pockets. 'Total eclipse expeditions are a relatively inexpensive way to obtain a variety of chromospheric and coronal information,' commented Professor Pasachoff. Such expeditions could also offer scientists a means to test equipment and methods that are intended for space launch.

So what does the future hold? Professor Pasachoff noted that ground-based capabilities will enable unique observations to be made from Earth, not space.

'Eventually, propinquity of spacecraft to the Sun, plus improvements of space solar telescopes in spatial, temporal and frequency domains may allow such space solar telescopes to take over completely, perhaps adding to observations of distant stellar coronas to explain the coronal heating problem,' he writes in his review.

'At present, the paired science and beauty of solar eclipses remain uniquely available to scientists and others in the path of totality [the path (up to 321 kilometres wide) that the Moon's shadow traces on the Earth during a total solar eclipse].'

More information:

  • Nature
  • Brno University of Technology

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