Indian astronomers have proved their resolve to go to even Antarctica to study the Sun! The Indian Institute of Astrophysics designed and built a solar telescope and together with the State Observatory in Nainital, set it up at Maitri, India’s permanent science base in Antarctica. The scientists were able to study solar oscillations and convection processes on the solar photosphere from Antarctica Continuous records of the evolution of super granules with a typical lifetime of 20 hours could be obtained.
The mission was part of the ninth Indian Antarctic Expedition in December 1989. The astronomers observed the Sun during the Antarctic Summer until March, 1990. As the Sun never sets during the Antarctic summer, continuous observation of solar features was possible. There was no interruption, as in a day and night cycle elsewhere on Earth. The astronomers also studied the phenomenon of convection on the solar surface, discovered by Robert Leighton and others in 1959.
A typical cell on the Photosphere has a dimension of 25,000 km and a lifetime of about 20 hours. The Indian astronomers found that they could be better seen as counterpart spectral lines at the chromospheric level in the well-known calcium line. Continuous observation is essential to understand the behaviour of the phenomenon, which is related to the solar magnetism.
As Antarctica has virtually no water vapour in the air and little atmospheric turbulence, several astrophysicists have pitched camps there to study the cosmic microwave background, a relic of the early Universe. A 2-m telescope there is equal to 8 metres elsewhere on Earth.
A robotic observatory at Dome Argus, the highest point in the Antarctic Plateau, has started functioning from February 2008. It is the coldest and driest place on Earth—believed to be the best location for ground-based astronomy called PLATO, it is built by University of South Wales (Australia), and installed by the Polar Research Institute of China with inputs from the US and UK. The telescope will look for planets orbiting Sun-like stars in the Milky Way. Its telescope will log on to an area in the sky, 100 times the size of a full Moon for four months at a stretch.
Is the Sun Not A Gas Giant?
The view that the Sun is a gaseous body gained acceptance, mostly because of a law that states that the pressure of a gas is proportional both to its temperature and density. The Sun was considered to have concentric gaseous shells obeying the law on gases. But it was the discovery of helium that seemed to have strengthened the gaseous view of the Sun.
Through traces of heavy elements (like carbon, sodium and iron) were found in the spectrum of solar and other rays, they were not considered indicators of a solid body inside the Sun. After all, even advanced telescopes showed the outer layers of the Sun as gaseous. This led a Swiss astronomer, Jacob Robert Emden (1862-1940) to declare that the Sun is a gaseous body throughout.
Satellite telescopes have, in the last ten years, punctured the image of the Sun as a gas giant. Yohkoh, SOHO and TRACE have peered through the outer layers of the Sun, a task that could not have been done by Galileo. What the satellites have found is astonishing: hard and highly defined structures that rotate uniformly (not at different speeds as seen by Galeleo) every 27.3 days.
Scientists have argued that the Sun cannot be very different from other stars in the Universe. The scientists point out the findings of satellite telescopes like Hubble, Chandra and Spitzer, which have peered into a wide range of galaxies and stars. Chandra, an X-ray satellite, for example, has found iron, calcium and silicon layers in the supernova remnants (explosions of stars). Harvard’s analysis of the data from Chandra has revealed the presence of iron and silicon when galaxies collide.
Dr. Kristian Birkeland has described an electrical model of the Sun, based on a solid core. Oliver Manuel has based his theory on the analysis of lunar samples from the Moon: he has indicated that the source of energy of the Sun is not the familiar hydrogen fusion, which became ‘fashionable’ after the atom was split, but calls the energy as ‘repulsive interaction between neutrons’ to describe the nuclear chemical reactions on the Sun.
New evidence for a solid core of the Sun has come from another finding: the source of solar wind blowing past the Earth’s magnetic envelope at supersonic speeds of 350 to 700 km per second. Initially it was thought the solar wind starts from the Sun’s corona, the topmost region of the solar ‘atmosphere’, which is seen only during a solar eclipse. But now scientists say the solar wind emanates from a lower region, called transitional layer, some 4000 km beneath the visible photosphere. The layer is believed to be a rocky ferrite layer, which emerges from an analysis of gigabytes of data returned by satellite telescopes.
Those who cynically say that there can be nothing new under the Sun have been proved wrong. Those who still think of the Sun as a gas giant would have to explain the contrary evidence, if they can. Galileo would have been the fist to change his views in the light of contrary evidence.