ESA's Sun-explorer Solar Orbiter reached its first perihelion, the point in its orbit closest to the star, on June 15, 2020, getting as close as 77 million kilometers (47.8 million miles) to the Sun's surface.
On July 16, ESA revealed the first close-up images that Solar Orbiter took of the Sun during an online press announcement. For the first time, the scientists discussed the first close-up images of the Sun, which we can see here below.
Solar Orbiter: International collaboration
Solar Orbiter is a space mission of international collaboration between the European Space Agency (ESA), NASA, and built in The United Kingdom. Nineteen ESA Member States (Austria, Belgium, The Czech Republic, Denmark, Finland, France, Germany, Greece, Italy, Ireland, Luxembourg, The Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland, and The United Kingdom), as well as NASA, contributed to the science payload and/or the spacecraft. The satellite was built by prime contractor Airbus Defence and Space in The United Kingdom.
“The first data are already demonstrating the power behind a successful collaboration between space agencies and the usefulness of a diverse set of images in unravelling some of the Sun’s mysteries,” said Holly Gilbert, Director of the Heliophysics Science Division at NASA Goddard Space Flight Center and Solar Orbiter Project Scientist at NASA.
First close-up images from Solar Orbiter reveal solar flares like campfires
The first images from Solar Orbiter, a new Sun-observing mission by ESA and NASA, have revealed omnipresent miniature solar flares, dubbed campfires, (video) near the surface of our closest star.
Phenomena such as these campfires were not observable in detail before. According to the scientists behind the mission, "this hints the enormous potential of Solar Orbiter, which has only just finished its early phase of technical verification known as commissioning."
These are only the first images, and we can already see interesting new phenomena," says Daniel Müller, ESA’s Solar Orbiter Project Scientist. "We didn’t really expect such great results right from the start. We can also see how our ten scientific instruments complement each other, providing a holistic picture of the Sun and the surrounding environment," he said.
According to ESA, Solar Orbiter (SolO), launched on February 10, 2020, carries six remote-sensing instruments or telescopes that image the Sun and its surroundings, and four in-situ instruments that monitor the environment around the spacecraft.
By comparing the data from both sets of instruments, scientists will be able to get insights into the generation of the solar wind, the stream of charged particles from the Sun that influences the entire Solar System.
It will take just under two years until the Solar Orbiter reaches its initial operational orbit, making use of gravity-assist flybys of Earth and Venus to enter the highly elliptical orbit around the Sun.
The unique aspect of the Solar Orbiter mission is that no other spacecraft has been able to take images of the Sun’s surface from such a closer distance.
Solar Orbiter's closest images of the Sun reveal new phenomena, which scientists call campfires
The campfires shown in the first image set were captured by the Extreme Ultraviolet Imager (EUI) from Solar Orbiter’s first perihelion, the point in its elliptical orbit that is closest to the Sun. When the spacecraft took the first images it was at only 77 million kilometers (47.8 million miles) away from the Sun, about half the distance between planet Earth and the star.
“The campfires are little relatives of the solar flares that we can observe from Earth, million or billion times smaller,” says David Berghmans of the Royal Observatory of Belgium (ROB), Principal Investigator of the EUI instrument.
The EUI instrument takes high-resolution images of the lower layers of the Sun’s atmosphere, known as the solar corona. “The Sun might look quiet at the first glance, but when we look in detail, we can see those miniature flares everywhere we look,” Berghmans said during the press announcement.
The scientists say that it is not clear yet whether the campfires are just tiny versions of big flares, or whether they are driven by different mechanisms. However, they already have theories that these miniature flares could be contributing to one of the most mysterious phenomena on the Sun: The coronal heating.
Solar Orbiter: Can the campfires unveil the Sun’s mysteries?
“These campfires are totally insignificant each by themselves, but summing up their effect all over the Sun, they might be the dominant contribution to the heating of the solar corona,” says Frédéric Auchère, of the Institut d'Astrophysique Spatiale (IAS), France, Co-Principal Investigator of EUI.
The solar corona is the outermost layer of the Sun’s atmosphere that extends millions of kilometres into outer space. Its temperature is more than a million degrees Celsius (a million and eight hundred thousand Fahrenheit), which is orders of magnitude hotter than the surface of the Sun, a cool 5.500 °C (9.932 °F). After many decades of studies, the physical mechanisms that heat the corona are still not fully understood, but identifying them is considered the holy grail of solar physics.
“It’s obviously way too early to tell but we hope that by connecting these observations with measurements from our other instruments that feel the solar wind as it passes the spacecraft, we will eventually be able to answer some of these mysteries,” says Yannis Zouganelis, Solar Orbiter Deputy Project Scientist at ESA.
Solar Orbiter: Seeing the far side of the Sun
The Polarimetric and Helioseismic Imager (PHI) is another cutting-edge instrument aboard Solar Orbiter. It makes high-resolution measurements of the magnetic field lines on the surface of the Sun. It is designed to monitor active regions on the Sun, areas with especially strong magnetic fields, which can give birth to solar flares.
During solar flares, the Sun releases bursts of energetic particles that enhance the solar wind that constantly emanates from the star into the surrounding space. When these particles interact with Earth’s magnetosphere, they can cause magnetic storms that can disrupt telecommunication networks and power grids on the ground.
“Right now, we are in the part of the 11-year solar cycle when the Sun is very quiet,” says Sami Solanki, the director of the Max Planck Institute for Solar System Research in Göttingen, Germany, and PHI Principal Investigator. “But because the Solar Orbiter is at a different angle to the Sun than Earth, we could actually see one active region that wasn’t observable from Earth. That is a first. We have never been able to measure the magnetic field at the back of the Sun,” he said.
The magnetograms, showing how the strength of the solar magnetic field varies across the Sun’s surface, could be then compared with the measurements from the in-situ instruments.
“The PHI instrument is measuring the magnetic field on the surface, we see structures in the Sun’s corona with EUI, but we also try to infer the magnetic field lines going out into the interplanetary medium, where Solar Orbiter is,” says Jose Carlos del Toro Iniesta, PHI Co-Principal Investigator, of Instituto de Astrofísica de Andalucía, Spain.
Solar Orbiter mission in Covid-19 times
The scientists were forced to restructure their work when lockdown hit the world. They had to stop the commissioning in the traditional way. Only two engineers could be at the control room keeping distance from each other. And the rest of the team would be working from home. "It was difficult, but it worked better than expected," one of the scientists said during the press briefing.
Catching the solar wind
The four in-situ instruments on Solar Orbiter characterize the magnetic field lines and solar wind as it passes the spacecraft.
Christopher Owen, of University College London Mullard Space Science Laboratory and Principal Investigator of the in-situ Solar Wind Analyser said that “using this information, they can estimate where on the Sun that particular part of the solar wind was emitted, and then "use the full instrument set of the mission to reveal and understand the physical processes operating in the different regions on the Sun which lead to solar wind formation.”
The U.K.'s key role in the development of the Solar Orbiter mission
The United Kingdom played a key role in the development of the Solar Orbiter mission. The spacecraft was built by Airbus Defence and Space in Stevenage. British scientists are involved in four out of the ten instruments aboard the spacecraft.
Researchers from Imperial College London and the UCL Mullard Space Science Laboratory (UCL MSSL) lead the teams behind Solar Orbiter’s Magnetometer (MAG) and Solar Wind Analyser (SWA) respectively.
UCL also has a key role in the Extreme Ultraviolet Imager (EUI), which will enable the scientists to study processes on the Sun in greater detail than ever before. STFC RAL Space led the consortium that developed and built the extreme ultraviolet imaging spectrometer SPICE.
The animation above shows five views of the Sun captured with the Extreme Ultraviolet Imager (EUI), and Polarimetric and Helioseismic Imager (PHI) instruments on ESA’s Solar Orbiter. The Sun is displaying only low levels of magnetic activity at the moment.
The image above shows the Sun's corona in ultra-violet light captured with the Extreme Ultraviolet Imager (EUI). The image shows two bright equatorial streamers and fainter polar regions which are characteristic of the solar corona during times of minimal magnetic activity.
The combination of a wide-angle view of the corona from the Metis instrument on ESA’s Solar Orbiter shows the full extent of the solar corona. The image above shows how the global scale solar magnetic field confines the plasma mostly near the equatorial belt, where the field lines are closed, giving rise to the bright streamers. Polar regions, where the magnetic field lines are open, exhibit a fainter brightness due the plasma outflow in the solar wind.
The Solar Orbiter will get closer to the Sun in less than two years' time. Future images will be even a little closer. In March 2022, the scientists will be expecting to receive from the Solar Orbiter data and images from the Sun with unprecedented resolution.
“We are all really excited about these first images – but this is just the beginning,” said Daniel Müller. “Solar Orbiter has started a grand tour of the inner Solar System, and will get much closer to the Sun within less than two years. Ultimately, it will get as close as 42 million kilometers (26 million miles), which is almost a quarter of the distance from Sun to Earth.”
- NASA/ESA Solar Orbiter to Release Closest Pictures of the Sun to Date