The blazing floor of the solar froths with a particularly sizzling electrically charged fuel known as plasma. The temperature on the fringe of this cosmic furnace runs at about 5,500 levels Celsius, however right here’s the actual puzzle: Somehow the solar’s ambiance, which surrounds that floor like a halo, is 150 occasions hotter.

“Why is the corona 1 million degrees while the photosphere is at 5,500?” asks Yannis Zouganelis, deputy venture scientist for the European Space Agency’s Solar Orbiter probe. “The main problem is, we have many ideas, many theories, but we have no real measurements.” 

Until now. Last yr, the Solar Orbiter swooped in for a close-up. It examined the corona from a distance of 140 million kilometers—shut sufficient to get good readings, however far sufficient away to not soften or harm its cameras. Even extra crucially, due to some astronomical choreography, engineers coordinated that maneuver with a flyby from NASA’s Parker Solar Probe to make the primary joint measurements of the corona. Together, they pulled off observations neither probe might have made by itself, Zouganelis says. Their findings have simply appeared in a brand new examine within the Astrophysical Journal Letters.

The ESA’s Solar Orbiter carries a coronagraph, an instrument known as Metis, developed by scientists on the Italian National Institute for Astrophysics. It blocks out mild from the solar’s floor, permitting the probe to take photographs solely of the corona. Imaging the corona intimately at optical and ultraviolet wavelengths permits scientists to review the dynamics inside that photo voltaic ambiance and higher perceive the heating charge inside it.

NASA’s probe maneuvered a lot nearer, about 9 million kilometers from the solar. That probe lacks cameras, however it could survive contained in the solar’s ambiance and make measurements of its plasma and magnetic fields. That permits scientists to trace how warmth and vitality transfer concerning the corona.

By utilizing each spacecraft collectively, researchers on the 2 groups had the possibility to mix simultaneous measurements and pictures. Most considerably, they decided that turbulence throughout the solar’s plasma contributes to the corona’s warmth—though they’re not but positive how a lot. Plasma is actually a fuel made from sizzling charged particles that emanate from the solar’s floor. As it roils in direction of the corona, it transmits warmth vitality outwards, a bit like how the flames of a hearth dissipate vitality as they flicker. 

“Combining the data from the two spacecraft, while they are aligned but far apart, gives us the evolution of the plasma from one spacecraft [reading] to the next. Having that information is so crucial,” says Nour Raouafi, the Parker Solar Probe venture scientist, who was not concerned within the analysis.

The new knowledge additionally offers perception into one other enigma that has stymied astrophysicists: How the photo voltaic wind accelerates to supersonic speeds. This wind is made up of charged particles flying alongside the solar’s magnetic discipline traces, which appear to be propelled into the photo voltaic system by small, intermittent, explosive jets on the base of the corona. Zouganelis and his ESA colleagues suppose that turbulence larger up the corona is probably going concerned in rushing it up, too. “They all work together to make the solar wind the way it is,” Raouafi says.