Three months after the flight of the balloon-borne solar observatory Sunrise, scientists from the Max Planck Institute for Solar System Research (MPS) in Germany now present unique insights into the central layer of the Sun’s atmosphere, the chromosphere.
Focus on the chromosphere: these images show the layer between the surface of the sun and the corona at a wavelength of 279.6 nanometers. Left: In this quiet region a typical pattern can be seen: dark areas surrounded by bright rims. The bright points flashing up here and there can be well discerned. Right: Close to sunspots the images show bright, stretched structures. The colours in these images stand for the intensity of the light: yellow means a high intensity, black a low intensity.
Zooming in on the sun: The right images shows a region of the chromosphere in close proximity to two sunspots. These images were taken on 16 July, 2013.
The Sunrise-data provide the first high-resolution images of this region, lying between the Sun’s visible surface and the corona, in ultraviolet light. More prominently than in earlier images, structures with a size of a few hundred kilometres such as bright points or strongly elongated fibrils occurring in close proximity to sunspots become visible in these wavelengths.
The chromosphere still continues to puzzle scientists. How is it possible that with increasing distance from the Sun’s hot core the temperature in this layer increases on average by 6000 Kelvin? "At first sight, this temperature distribution contradicts basic physical concepts", says Sami K. Solanki, head of the Sunrise mission and director at the MPS. The situation can be compared to a heated room in which it gets warmer with increasing distance to the heater. “Apparently, the chromosphere witnesses huge energy transformations”, he adds. “Processes not yet understood in detail must provide enough energy to heat up the plasma." Data from Sunrise’s first mission in 2009 had revealed acoustic waves to supply a considerable fraction of this energy. In addition, research carried out in recent years has characterized the chromosphere as a very dynamical place where hot and colder regions may lie in close proximity and are constantly in motion.
"In order to solve this riddle it is necessary to take as close a look as possible at the chromosphere – in all accessible wavelengths", Solanki explains. Together with colleagues from the Kiepenheuer-Institut für Sonnenphysik (Freiburg, Germany), the High Altitude Observatory (Boulder, USA), and the Instituto de Astrofísica de Andalucía (Granada, Spain) the MPS researchers were now able to fit another piece into the puzzle: the first high-resolution observations of the chromosphere in ultraviolet light.
The images were made possible by Sunrise, a balloon-borne solar observatory studying the Sun from the stratosphere. Once it reaches its float altitude of more than 37 kilometres, Sunrise has risen above the greatest part of the Earth’s atmosphere. These layers absorb the Sun’s ultraviolet radiation, making it inaccessible to ground-based solar observations. At the beginning of June of this year Sunrise was launched from Kiruna in the north of Sweden and embarked on its second journey. After five days the observatory landed on the remote Boothia Peninsula in northern Canada.
"Of course, in the past space probes have analysed the Sun’s ultraviolet light from space", says Solanki. However, they provide a lower spatial resolution. And Sunrise offers another decisive advantage: the Sunrise Filter Imager, one of the onboard scientific instruments, is able to filter certain ultraviolet parts out of the solar spectrum – for example the radiation with a wavelength of 279.6 nanometres. "Only the magnesium atoms in the chromosphere emit this radiation", says Tino Riethmüller from the MPS, the new study’s leading author. "Even though magnesium constitutes only 0.0024 percent of the Sun’s mass, it gives us direct access to this region", he adds.
The new data paint a complex picture of the chromosphere: where the Sun is quiet and inactive, dark regions with a diameter of around a thousand kilometres can be discerned surrounded by bright rims. This pattern is created by the enormous plasma flows rising up within the Sun, cooling off and sinking down again. Especially eye-catching are bright points that flash up occasionally. In the ultraviolet images they are much richer in contrast than before. Scientists believe these bright points to be signs of single magnetic flux tubes in the photosphere, the building blocks of the solar magnetic field. The Sun’s magnetic field is of particular interest to scientists since it is responsible for all of the star’s activity.
Apart from these quiet regions the researchers also focused on areas in close proximity to sunspots. These huge structures cover the Sun’s surface especially abundantly in times of high solar activity. “In our images we find bright, strongly elongated structures called fibrils”, says Riethmüller.
"These first analyses are extremely promising", Solanki comments the new results. "They show that the ultraviolet radiation from the chromosphere is highly suitable for visualizing detailed structures and processes." The researchers now hope that the next months will provide more new insights – and are looking forward to a close collaboration with colleagues from NASA’s IRIS mission. The space telescope was launched on 28 June, only weeks after the end of the Sunrise mission, and also studies the ultraviolet radiation from chromosphere and corona.
ContactDr. Birgit Krummheuer
Dr. Birgit Krummheuer | Max-Planck-Institute
Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst
Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy