IR Modeling Proves the Sun's in Hot Water

Charles T. Troy

WATERLOO, Ontario, Canada -- By comparing the infrared spectra of sunspots and a simulation of infrared spectra of very hot water, scientists have confirmed that very hot water does indeed exist in sunspots.

Fiery eruptions on the sun, captured by NASA and the European Space Agency's Solar and Heliospheric Observatory spacecraft, occur in 11-year cycles.

A multinational research team from Canada, the UK and Russia not only confirmed the belief that water exists on the sun, but also clearly demonstrated the power of spectral analysis based on variational treatment of nuclear motions in a molecule.
In 1995 the team found evidence of water in the form of steam -- the sun is approximately 5800 K -- in dark sunspots. The evidence consisted of laboratory spectra of hot water (approximately 1800 K) that matched that of the sunspots.
Hot water has a complicated infrared spectrum characterized by a dense series of sharp absorption lines, but the transitions that give rise to those lines previously were unknown. The simulation allowed accurate assignment of those absorption lines.

Brute force solutions
Peter F. Bernath, a chemist at the University of Waterloo, said that the team employed a "brute force solution of the vibration-rotation motion on a computer, without making any of the usual simplifying assumptions." The heart of the work was the collaboration with UK and Russian theoreticians that provided detailed mathematical interpretations of the spectrum.
According to Bernath, the laboratory spectra and the new calculations match the sunspot spectrum, enabling a prediction of the absorption or emission infrared spectrum of hot water at any temperature and confirming the researchers' earlier assumptions.
Practical applications of the work are expected in modeling of infrared emissions and absorption of combustion systems such as forest fires and engine exhausts.