The first images of Solar Orbiter, the new mission of the European Space Agency to observe the Sun, have revealed the presence of multitudes of solar mini-eruptions near its surface. The spacecraft has also provided the first autonomous magnetic map of our star obtained from space.
After its launch on February 10, the Solar Orbiter mission of the European Space Agency (ESA), in collaboration with NASA, has begun to send its spectacular images of the Sun, the closest captured so far of our star.
"These are just the first images and we can already see new phenomena of interest," says Daniel Müller, a scientist for ESA's Solar Orbiter project. "We did not expect such good results from the beginning, and we have also been able to see how the ten scientific instruments complement each other, offering a comprehensive image of the Sun and its surroundings."
Solar Orbiter includes six remote sensing instruments (telescopes), which will observe the Sun and its surroundings, and four instrumentsin situ to survey the environment around the ship. By comparing the data from both classes of instruments, information will be obtained about how the solar wind is generated, the shower of charged particles from the Sun that affects the entire solar system.
But what makes Solar Orbiter unique is that, until now, no other mission has been able to take pictures from this close to the solar surface.
One of the results is the 'bonfires' that appear in the photographs captured by the Extreme Ultraviolet Imaging Camera (EUI) during the first perihelion of Solar Orbiter, the point in its elliptical orbit closest to the Sun. At that time, the The spacecraft was only 77 million kilometers from the Sun, about half the distance between Earth and our star.
"These bonfires are like minor relatives of solar flares observed from Earth, but millions to billions of times smaller," says David Berghmans, from the Royal Observatory of Belgium (ROB) and principal investigator of the EUI instrument, which takes high-resolution images of the lower layers of the solar atmosphere, or corona. "At first glance, the Sun may appear immobile, but when you look at it in detail, we can see these little flares everywhere."
The mysterious warming of the crown
Researchers still don't know if these are tiny versions of large flares or if they are due to different mechanisms. In any case, there are already theories that these "small" eruptions could contribute to one of the most enigmatic phenomena on the Sun: the heating of the corona.
“Each of these bonfires is insignificant by itself, but if we add their effect across the entire surface, they could contribute significantly to the heating of the solar corona,” explains Frédéric Auchère, from the French Institute for Space Astrophysics (IAS) and EUI lead co-investigator.
The solar corona is the outermost layer of the Sun's atmosphere, stretching millions of kilometers into outer space. Its temperature exceeds a million degrees Celsius, several orders of magnitude hotter than the surface of the Sun, which is "just" at 5,500 ° C. After decades of study, the physical mechanisms that heat the corona are still not fully understood, but identifying them is considered the 'holy grail' of solar physics.
"Obviously, it is too early to know, but we are confident that, by linking these observations with measurements from the rest of the instruments that study the solar wind passing by the spacecraft, we can solve some of these mysteries," says Yannis Zouganelis, Associate Scientist for ESA's Solar Orbiter Project.
For its part, the Polarimetric and Helioseismic Imaging Camera (PHI) is another advanced instrument on board Solar Orbiter. It makes high-resolution measurements of the magnetic field lines on the solar surface. It is designed to monitor active regions of the Sun, areas with particularly strong magnetic fields that could lead to flares.
During these flares, the Sun releases bursts of energetic particles that strengthen the solar wind that the star constantly releases into space. When these particles interact with the Earth's magnetosphere, they can cause magnetic storms capable of disrupting telecommunications networks and electrical infrastructures on the ground.
"Right now we are in a part of the eleven-year solar cycle in which the Sun is very calm," clarifies Sami Solanki, director of the Max Planck Institute for Solar System Research in Göttingen (Germany) and principal investigator at PHI. “But since the Solar Orbiter is at a different angle to the Sun from that of the Earth, we could see an active region not observable from our planet. That is something totally new; Until now we have never been able to measure the magnetic field on the far side of the Sun ”.
Magnetograms, which show how the intensity of the magnetic field varies across the solar surface, could then be compared with measurements from instruments.in situ. For now, the ship has already providedhis first magnetic map of the Sun, which is also the first obtained autonomously, that is, from space and without human intervention.
"The PHI instrument measures the magnetic field on the surface, while with EUI we see structures in the solar corona, but we also try to infer the magnetic field lines that extend to the interplanetary medium, where the Solar Orbiter is located", explains José Carlos del Toro Iniesta, from the Andalusian Institute of Astrophysics and PHI co-principal investigator.
"The image obtained with the high-resolution telescope provides the first autonomous magnetogram made in space," the researcher emphasizes.
Capturing the solar wind
Furthermore, the four instrumentsin situ Solar Orbiter's have begun to characterize the magnetic field lines and the solar wind passing past the spacecraft.
Christopher Owen of the Mullard Space Science Laboratory at University College London and Principal Investigator of the Solar Wind Analyzerin situ (SWA), adds: “With this information we can calculate from where on the Sun that particular portion of the solar wind was emitted, and then use the mission's set of instruments to reveal and understand the physical processes that operate in the different regions of the world. Sun and that give rise to the formation of the solar wind ”.
"We are very excited about these first images, but they are only the beginning," adds Müller. “Solar Orbiter has started a long journey through the inner solar system, and in less than two years it will get much closer to the Sun. In the end, it will approach only 42 million kilometers, which is almost a quarter of the distance of the Earth to the Sun ”.
Solar Orbiter is a space mission fruit of the international collaboration between ESA and NASA. Twelve ESA Member States (Germany, Austria, Belgium, Spain, France, Italy, Norway, Poland, the United Kingdom, the Czech Republic, Sweden and Switzerland), as well as NASA, have contributed to the scientific payload. The satellite has been built by the main contractor, Airbus Defense and Space, in the UK.
Spanish researchers play a prominent role in two of the ten instruments on board the ship: the energetic particle detector (EPD), led by the University of Alcalá and the University of Kiel (Germany); and the PHI magnetograph led by the IAA and the Max Planck Institute for Solar System Research (Göttingen, Germany).
Source:ESA / CSIC / INTA