This image — the closest ever taken of the Sun — shows the corona teeming with thousands of miniature solar flares, which scientists have dubbed campfires. The pictures are the first released from the Solar Orbiter mission, led by the European Space Agency.
“When the first images came in, my first thought was this is not possible, it can’t be that good,” David Berghmans, principal investigator for the orbiter’s Extreme Ultraviolet Imager instrument, told a press briefing on 16 July. “It was much better than we dared to hope for.”
“The Sun might look quiet at the first glance, but when we look in detail, we can see those miniature flares everywhere we look,” said Berghmans, a solar physicist at the Royal Observatory of Belgium in Brussels, in a statement.
The fires are just millionths or billionths of the size of the solar flares visible from Earth, which are energetic eruptions thought to be caused by interactions in the Sun’s magnetic fields. The mission team has yet to work out whether the two phenomena are driven by the same process, but the researchers speculate that the combined effect of the many campfires could contribute to the searing heat of the corona, the Sun’s outer atmosphere. The corona is hundreds of times hotter than the Sun’s surface, but the reason is a long-standing mystery.
The pictures, taken by the ultraviolet imager on 30 May and released on 16 July, were captured 77 million kilometres from the Sun’s surface (Earth is about 150 million kilometres from the Sun). A daring NASA mission called the Parker Solar Probe has flown even closer and will get within just 6.2 million kilometres during its mission — inside the corona itself — but the environment is so harsh that it does not carry a camera facing the Sun. Meanwhile, on Earth, the Daniel K. Inoye Solar Telescope in Hawaii has taken higher-resolution images of the Sun than the orbiter, but these do not fully capture the star’s light, because Earth’s atmosphere filters out some ultraviolet and X-ray wavelengths.
Scientists are excited about the potential of the Solar Orbiter, an international collaboration that launched in February and carries ten instruments to image the Sun and study its environment. The spacecraft will eventually switch its orbit to study the Sun’s polar regions for the first time. “We’ve never been closer to the Sun with a camera, and this is just the beginning of a long epic journey with Solar Orbiter, which will take us even closer to the Sun in two years’ time,” said Daniel Müller, the mission’s project scientist, at the briefing.