Solar astronomers are scientists who observe and study the Sun, our local star. Because it is so close and bright, they are able to acquire much more detailed information about the Sun than night-time astronomers can of more distant stars. Understanding the physical processes of the Sun thus has profound benefit to the understanding of all stars, the building blocks of galaxies and of much of the visible matter in the universe. One of the primary goals of solar astronomy is to understand, in the greatest possible detail, how the magnetic fields and other processes in the Sun affect the emission of energetic particles and of heat, light, and higher energy forms of electromagnetic radiation such as ultraviolet light and X-rays. These emitted particles and light are interesting to study from a purely scientific point of view, but they also have great relevance to life on Earth. The Sun creates "space weather" - the environment surrounding planet Earth. Understanding and predicting how observed changes in the Sun's characteristics will affect the Earth's environment is crucial to mankind.
In order to see the fine detail that can reveal the secrets of the Sun's magnetism, it is necessary to have a solar telescope with very high resolving power. However, telescopes on the ground must observe the Sun through the interference of the Earth's atmosphere. As light passes through the atmosphere it gets spread out by turbulence due to wind shear and changes in temperature and pressure within the atmospheric layers. These effects reduce the resolving power of Earth-based telescopes. This difficulty can be overcome to a large extent by relatively new techniques employing Adaptive Optics (AO) where several small patches on the sun are monitored for changes induced by our atmosphere. These changes are rapidly detected (over 100 times per second) and the correlation among the patches tells us how the Earth's atmosphere is distorting the light. This information is then fed into special adjustable optics in the telescope to restore the image to (nearly) what could be seen from above the Earth's atmosphere.
Dr. Philip Goode of the New Jersey Institute of Technology and his team are developing a sophisticated AO system for the New Solar Telescope at Big Bear Solar Observatory in the San Bernadino Mountains in Southern California. This telescope is located on a pier literally in Big Bear Lake where the lake's water ensures that the air surrounding the telescope is stable. This new telescope with Adaptive Optics will provide the best resolved images of the Sun ever delivered on the shortest time scales ever measured. The analysis of these data is sure to lead to a better understanding of our local star and of the space weather it causes.
Images of the Sun from the Earth are distorted by the Earth's turbulent atmosphere, which has limited our efforts to understand the nature of our star. In recent years, the technology of adaptive optics has enabled us to circumvent the effects of atmospheric turbulence on tthese images. The heart of the technology has is deformable mirrors (DMs) that change shape 100's of times a second to compensate for the distortion. Sensing the disorted sunlight and using tranforming that signal to commands to distort the DM to compensate for the atmospheric effect requires a considerable effort in processing a torrent of wavefront data at the telescope to control the DM. Our first generation adaptive optics (AO) system produced the image shown in the first figure (Summer 2010). At the time, this was cited by the editors of National Geographic as one of the top ten space images of 2010. Still, we needed a second generation AO system to take full advantage of the 1.6 m off-axis solar telescope we built in Big Bear. The telescope is the highest resolution solar telescope ever built. In our ATI project, we more than tripled the AO systems ability to correct disotrted sunlight. A new DM and a considerable programming effort, but it paid off with images like the one shown in the second figure. What is apparent in the center of the Summer 2013 image is the fine structures, which are absent in the 2010 image. For instance, in the 2013 sunspot one can see dark a much greater richness in the dark center of the sunspot. We even see dark centers in the bright (umbral) dots in the dark sunspot center. We also used the telescope to discover a new kind of large-scale magnetic loops -- ten times narrower and ten times cooler than any previously seen from the ground or space. AO was critical here, and is now being used to probe the dynamical event that cause "space weather" events that can impact satellites and terrestrial communications, as well as the electric power grid.
