The Euro-American Solar Orbiter probe delivered on Thursday the closest images ever taken of the Sun. She unveiled miniature eruptions called “campfires”, which could explain the heating of the solar corona, a phenomenon still mysterious.
The Solar Orbiter mission, in collaboration with the European Space Agency (ESA) and NASA, launched on February 10 towards the Sun. On board ten instruments including six observation telescopes give the spacecraft a unique ability to take images of the solar surface.
“The Sun had never been taken so close!”, Congratulated AFP Anne Pacros, mission and payload manager. At 77 million kilometers from the star (about half of the Earth-Sun distance), the first close-up images have highlighted a new phenomenon: “campfires”, ubiquitous mini-solar flares near the surface, detailed ESA at a press conference.
«Eruptions miniatures»
These “campfires”, which until now were not visible in detail, “are small compared to the giant solar flares that we can observe from Earth, millions or billions of times smaller”, explained David Berghmans from the Royal Observatory of Belgium, principal investigator of the “Extreme Ultraviolet Imager” (EUI) remote sensing instrument, which took images in extreme ultraviolet radiation.
“The Sun may seem calm at first glance, but when we look in detail we can see these miniature flares everywhere we look,” he added.
Scientists still do not know whether these “campfires” are a simple miniature version of large eruptions, or the result of different mechanisms. But theories already claim that they “could contribute to the heating of the solar corona”, a phenomenon so far unexplained, explains ESA.
The solar corona, the most extreme layer of the Sun’s atmosphere which extends over millions of kilometers in space, in fact exceeds a million degrees while the surface of the Sun reaches “only” 5,500 degrees: this gigantic gap defies the laws of nature, which would like that the more one moves away from a source of heat, the more the temperature drops. Understanding these mechanisms is considered to be the “Grail” of solar physics, emphasizes ESA.
A large Swiss participation
Installed on board the “Solar Orbiter”, the STIX X-ray telescope was produced by Swiss companies and research institutes, in collaboration with partners from Poland, France, Czech Republic, Germany, Austria, Ireland and Italy. The University of Applied Sciences of North-West Switzerland (FHNW) oversees the project.
In Switzerland, the University of Bern and the Paul Scherrer Institute are among these contributors, as well as some fifteen companies, including two in French: Almatech SA, in Lausanne, and Niklaus SA, in Meyrin (GE).
STIX (Spectrometer Telescope for Imaging X-rays) will record not only images, but also spectra of X-rays emitted by the Sun. This data will provide information on the physical states and processes that occur during solar flares.
The FHNW in Windisch (AG) is responsible for the development, construction, operation and scientific evaluation of STIX, under the direction of Professor Säm Krucker.
Two other instruments
In addition to STIX, Switzerland is participating in two other instruments on the probe – EUI (Extreme Ultraviolet Image) and SPICE (Spectral Imaging of the Coronal Environment) – under the supervision of the PMOD / WRC observatory in Davos (GR). This world-class institution specializes in the study of the Sun.
The EUI instrument must deliver sequences of images of the different atmospheric layers of the Sun. It has three telescopes with ultra-violet cameras.
SPICE, also in ultraviolet, aims to characterize the plasma properties of the solar corona. The aim is to identify signatures in the composition of the solar winds in relation to their regions of origin on the surface of the star.
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