SUNRISE Telescope Delivers Spectacular Pictures of Sun Surface 

Grainy sun: the images show the so-called granulation in four different wavelengths in near ultraviolet light. The image section depicts 1/20,000 of the entire surface. The smallest recognizable structures have an angular resolution equal to that of looking at a coin from a distance of 100 kilometers. The light structures are the foundational elements of the magnetic fields. Courtesy of MPI for Solar System Research

The Sun is a bubbling mass. Packages of gas rise and sink, lending the sun its grainy surface structure, its granulation. Dark spots appear and disappear, clouds of matter dart up — and behind the whole thing are the magnetic fields, the engines of it all. The SUNRISE balloon-born telescope has delivered images that show the complex interplay on the solar surface to a level of detail never before achieved.

A collaborative project between the Max Planck Institute for Solar System Research (MPS) in Katlenburg-Lindau and partners in Germany, Spain and the USA, the largest solar telescope ever to have left Earth was launched from the ESRANGE Space Centre in Kiruna, northern Sweden, on June 8, 2009. The total equipment weighed in at more than six tons on launch. Carried by a gigantic helium balloon with a capacity of a million cubic meters and a diameter of around 130 meters, SUNRISE reached a cruising altitude of 37 kilometers above the Earth’s surface.

The observation conditions in this layer of the atmosphere, known as the stratosphere, are similar to those in outer space: for one thing, the images are no longer affected by air turbulence; and for another, the camera also can zoom in on the Sun in ultraviolet light, which would otherwise be absorbed by the ozone layer. After separating from the balloon, SUNRISE parachuted safely down to Earth on June 14th, landing on Somerset Island, a large island in Canada’s Nunavut Territory situated in the Northwest Passage.

The work of analyzing the total of 1.8 terabytes of observation data recorded by the telescope during its five-day flight has only just begun. Yet, the first findings already give a promising indication that the mission will bring our understanding of the Sun and its activity a great leap forward. What is particularly interesting is the connection between the strength of the magnetic field and the brightness of tiny magnetic structures. Since the magnetic field varies in an 11-year cycle of activity, the increased presence of these foundational elements brings a rise in overall solar brightness — resulting in greater heat input to the Earth.

The variations in solar radiation are particularly pronounced in ultraviolet light. This light does not reach the surface of the Earth; the ozone layer absorbs and is warmed by it. During its flight through the stratosphere, SUNRISE carried out the first-ever study of the bright magnetic structures on the solar surface in this important spectral range with a wavelength of between 200 and 400 nanometers (millionths of a millimeter).

The IMaX instrument not only depicts the solar surface, it also makes magnetic fields visible; these appear as black or white structures in the polarized light. SUNRISE enables tiny magnetic fields on the surface of the Sun to be measured at a level of detail never before achieved. Courtesy of MPS/IMAX consortium

“Thanks to its excellent optical quality, the SUFI instrument was able to depict the very small magnetic structures with high intensity contrast, while the IMaX instrument simultaneously recorded the magnetic field and the flow velocity of the hot gas in these structures and their environment,” says Achim Gandorfer, project scientist for SUNRISE at the Max Planck Institute for Solar System Research.

Previously, the observed physical processes only could be simulated with complex computer models. “Thanks to SUNRISE, these models can now be placed on a solid experimental basis,” explains Manfred Schüssler, solar scientist at the MPS and co-founder of the mission.

In addition to the Max Planck Institute for Solar System Research, numerous other research facilities also are involved in the SUNRISE mission:

• Kiepenheuer Institute for Solar Physics in Freiburg

• High Altitude Observatory in Boulder, Colorado

• Instituto de Astrofisica de Canarias on Tenerife

• Lockheed-Martin Solar and Astrophysics Laboratory in Palo Alto, California

• NASA’s Columbia Scientific Ballooning Facility

• ESRANGE Space Centre.

The project is funded by the Federal Ministry of Economics through the German Aerospace Centre (DLR).