The first images from Solar Orbiter, the new sun-observing mission by the European Space Agency (ESA) and NASA, have revealed miniature solar flares, dubbed “campfires,” near the surface of our star.
“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.”
No other spacecraft has been able to take images of the sun’s surface from a closer distance.
The new images hint at the enormous potential of Solar Orbiter, which only just finished its early phase of technical verification, according to the scientists behind the mission.
The Solar Orbiter, which launched in February 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 get insights into the generation of the solar wind, the stream of charged particles from the sun that influences the entire Solar System.
The campfires shown above were captured by the Extreme Ultraviolet Imager (EUI) from Solar Orbiter’s first perihelion, the point in its elliptical orbit closest to the sun. At that time, the spacecraft was only 77 million km away from the sun, about half the distance between Earth and the star.
“We are all really excited about these first images – but this is just the beginning,” added Daniel. “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 km, which is almost a quarter of the distance from Sun to Earth.”
“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, which 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.”
The scientists do not know yet whether the campfires are just tiny versions of big flares, or whether they are driven by different mechanisms. There are, however, already theories that these miniature flares could be contributing to one of the most mysterious phenomena on the sun, the coronal heating.
The solar corona is the outermost layer of the sun’s atmosphere that extends millions of kilometers into outer space. Its temperature is more than a million degrees Celsius, which is orders of magnitude hotter than the surface of the sun, a “cool” 5500 °C. 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,” said Yannis Zouganelis, Solar Orbiter Deputy Project Scientist at ESA.
A high-resolution image from the Extreme Ultraviolet Imager (EUI) on ESA’s Solar Orbiter spacecraft, taken with the HRIEUV telescope on 30 May 2020. These images show the Sun’s appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Images at this wavelength reveal the upper atmosphere of the Sun, the corona, with a temperature of around 1 million degrees. (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
A high-resolution image from the Extreme Ultraviolet Imager (EUI) on ESA’s Solar Orbiter spacecraft, taken with the HRIEUV telescope on 30 May 2020. These images show the Sun’s appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Images at this wavelength reveal the upper atmosphere of the Sun, the corona, with a temperature of around 1 million degrees. (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
A high-resolution image from the Extreme Ultraviolet Imager (EUI) on ESA’s Solar Orbiter spacecraft, taken with the HRIEUV telescope on 30 May 2020. These images show the Sun’s appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Images at this wavelength reveal the upper atmosphere of the Sun, the corona, with a temperature of around 1 million degrees. (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
The Extreme Ultraviolet Imager (EUI) on ESA’s Solar Orbiter spacecraft took these images on 30 May 2020. They show the Sun’s appearance at a wavelength of 17 nanometers, which is in the extreme ultraviolet region of the electromagnetic spectrum. Images at this wavelength reveal the upper atmosphere of the Sun, the corona, with a temperature of around 1 million degrees. 
The Heliospheric Imager (SoloHI) telescope on ESA’s Solar Orbiter spacecraft takes images of the solar wind – the stream of charged particles constantly released by the Sun into outer space – by capturing the light scattered by electrons in the wind. This image is a mosaic of four separate images from four separate detectors, obtained during the instrument’s ‘first light’ on 5 June 2020. Then, Solar Orbiter was at a distance of 0.5 astronomical units (AU; one AU is equivalent to the average distance from Earth to the Sun, about 150 million kilometres) from the Sun. SoloHI is looking off to the left side of the Sun, 5 to 45 degrees from Sun center, which at 0.5 AU corresponds to about 10 to 85 times the solar radius, or 0.04 AU to 0.39 AU. The Sun is located to the right of the frame, and its light is blocked by a series of baffles that reject the sunlight by a factor of a trillion (1012). The last baffle is in the field of view on the right-hand side and is illuminated by reflections from the solar array. “This first light image is amazing and the stray light is what we have modeled,” says Russell Howard, the SoloHI Principal Investigtor from the US Naval Research Laboratory in Washington, DC. “I can hardly wait to see the real science images.” (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
These solar images have been produced by the high resolution imager, HRILYA telescope, which is part of the Extreme Ultraviolet Imager (EUI) instrument on ESA’s Solar Orbiter spacecraft. The images show the solar surface in a particular ultraviolet wavelength that is produced by hydrogen, the most abundant chemical element in the Universe. The wavelength is known as Lyman-alpha and has a wavelength of 121.6 nm. Here, it shows the solar atmosphere below the hot corona revealed by EUI’s HRIEUV telescope. The ‘network’ structure seen in the images is characteristic of a region of the solar atmosphere known as the chromosphere. This section of the Sun’s lower atmosphere has a temperature of about ten-thousand to hundred-thousand degrees Kelvin. It is an important transition region in the solar atmosphere where the electrically charged gas, known as plasma, is increasingly dominated by the magnetic field of the Sun. The pattern is produced by convective motions underneath, but individual bright features within this pattern can correspond to the footprints of magnetic structures higher up in the corona. The violet color has been artificially added to help visual identification of this region. (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
These solar images have been produced by the high resolution imager, HRILYA telescope, which is part of the Extreme Ultraviolet Imager (EUI) instrument on ESA’s Solar Orbiter spacecraft. The images show the solar surface in a particular ultraviolet wavelength that is produced by hydrogen, the most abundant chemical element in the Universe. The wavelength is known as Lyman-alpha and has a wavelength of 121.6 nm. Here, it shows the solar atmosphere below the hot corona revealed by EUI’s HRIEUV telescope. The ‘network’ structure seen in the images is characteristic of a region of the solar atmosphere known as the chromosphere. This section of the Sun’s lower atmosphere has a temperature of about ten-thousand to hundred-thousand degrees Kelvin. It is an important transition region in the solar atmosphere where the electrically charged gas, known as plasma, is increasingly dominated by the magnetic field of the Sun. The pattern is produced by convective motions underneath, but individual bright features within this pattern can correspond to the footprints of magnetic structures higher up in the corona. The violet color has been artificially added to help visual identification of this region. (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
These solar images have been produced by the high resolution imager, HRILYA telescope, which is part of the Extreme Ultraviolet Imager (EUI) instrument on ESA’s Solar Orbiter spacecraft. The images show the solar surface in a particular ultraviolet wavelength that is produced by hydrogen, the most abundant chemical element in the Universe. The wavelength is known as Lyman-alpha and has a wavelength of 121.6 nm. Here, it shows the solar atmosphere below the hot corona revealed by EUI’s HRIEUV telescope. The ‘network’ structure seen in the images is characteristic of a region of the solar atmosphere known as the chromosphere. This section of the Sun’s lower atmosphere has a temperature of about ten-thousand to hundred-thousand degrees Kelvin. It is an important transition region in the solar atmosphere where the electrically charged gas, known as plasma, is increasingly dominated by the magnetic field of the Sun. The pattern is produced by convective motions underneath, but individual bright features within this pattern can correspond to the footprints of magnetic structures higher up in the corona. The violet color has been artificially added to help visual identification of this region. (Solar Orbiter/EUI Team (ESA & NASA); CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL) 
A close-up image taken with the Polarimetric and Helioseismic Imager (PHI) High Resolution Telescope on ESA’s Solar Orbiter on 28 May 2020. The area is approximately 200 000 km x 200 000 km across and is centred on the middle of the Sun. It shows the Sun’s granulation pattern that results from the movement of hot plasma under the Sun’s visible surface. (Solar Orbiter/PHI Team/ESA & NASA) 
This full disc image shows a map of magnetic propertied for the whole Sun based on data from the Polarimetric and Helioseismic Imager (PHI) on ESA’s Solar Orbiter. Taken on 18 June 2020, there is a large magnetically active region in the lower right-hand quadrant of the Sun. (Solar Orbiter/PHI Team/ESA & NASA) 
This image is a ‘tachogram’ of the Sun, taken with the Polarimetric and Helioseismic Imager (PHI) Full Disc Telescope on ESA’s Solar Orbiter on 18 June 2020. It shows the line of sight velocity of the Sun, with the blue side turning to us and the red side turning away. (Solar Orbiter/PHI Team/ESA & NASA) 
This image is a view of the Sun taken by the Polarimetric and Helioseismic Imager (PHI) Full Disc Telescope on ESA’s Solar Orbiter on 18 June 2020. This is a visible light image and represents what we would see with the naked eye. There are no sunspots visible because the Sun is displaying only low levels of magnetic activity at the moment. (Solar Orbiter/PHI Team/ESA & NASA) 
An image of the Sun’s corona obtained with the Metis instrument on ESA’s Solar Orbiter. This was obtained on 21 June 2020, shortly after the spacecraft’s first perihelion, and was taken in visible light (580-640 nm). It shows the two bright equatorial streamers and fainter polar regions that are characteristic of the solar corona during times of minimal magnetic activity. (Solar Orbiter/PHI Team/ESA & NASA) 
An image of the Sun’s corona obtained with the Metis instrument on ESA’s Solar Orbiter. This was obtained on 21 June 2020, shortly after the spacecraft’s first perihelion, and was taken in visible light (580-640 nm). It shows the two bright equatorial streamers and fainter polar regions that are characteristic of the solar corona during times of minimal magnetic activity. (Solar Orbiter/PHI Team/ESA & NASA)
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 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.”
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 or the spacecraft.
