Washington, D.C .:
The first images from ESA / NASA's Solar Orbiter, a new solar observation mission, are now available to the public, including the next images ever taken by the sun.
Solar Orbiter is an international collaboration between the European Space Agency (ESA) and NASA to study our next star, the Sun. The spacecraft, launched on February 9, 2020 (EST), completed its first narrow pass of the sun in mid-June.
"These unprecedented images of the sun are the closest we've ever received," said Holly Gilbert, NASA project scientist for the mission at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
"These amazing images will help scientists put together the atmospheric layers of the sun, which is important to understand how space weather drives near Earth and throughout the solar system," added Gilbert.
"We weren't expecting such great results so early. These pictures show that Solar Orbiter got off to a great start," said Daniel Muller, solar scientist at ESA's Solar Orbiter project.
Getting to this point was not an easy task. The novel corona virus forced mission control at the European Space Operations Center (ESOC) in Darmstadt, Germany, to close completely for more than a week.
During commissioning, the time in which each instrument was extensively tested, the ESOC staff was reduced to a skeleton crew. All but the necessary staff worked from home.
"The pandemic required us to do critical operations remotely – the first time we did," said Russell Howard, lead researcher for one of Solar Orbiter's imagers.
But the team adapted and even prepared for an unexpected encounter with the ion and dust tails of the comet ATLAS on June 1st and 6th.
The spacecraft finished commissioning on time for its first sun pass on June 15th. When it flew around the sun within 48 million miles, all 10 instruments turned on and Solar Orbiter took the next sun pictures so far. (Other spaceships were closer, but none of them wore sun pictures.)
Solar Orbiter has six imaging instruments, each of which examines a different aspect of the sun. Usually, the first pictures of a spacecraft confirm that the instruments are working. Scientists do not expect new discoveries from them. However, the Extreme Ultraviolet Imager (EUI) on Solar Orbiter provided data indicating solar characteristics that have never been observed in such detail.
Lead investigator David Berghmans, astrophysicist at the Royal Observatory of Belgium in Brussels, points out what he calls EUI images "bonfire" that punctures the sun.
"The campfires we are talking about are the little nephews of solar flares, at least a million, maybe a billion times smaller. If you look at the new high-resolution EUI images, they are literally everywhere we look," said Berghmans .
It is not yet clear what these campfires are or how they correspond to the sun brightening observed by other spacecraft. But it's possible that they're mini-explosions known as nanoflares – tiny but ubiquitous sparks that theoretically help to heat the sun's outer atmosphere or corona to its temperature, 300 times hotter than is the surface of the sun.
To be sure, scientists need a more accurate measurement of the campfire temperature. Fortunately, the Spectral Imaging of the Coronal Environment or the SPICE instrument, also on Solar Orbiter, does just that.
"So we are eagerly awaiting our next data set. The hope is to reliably detect nanoflares and to quantify their role in coronal warming," said Frederic Auchere, lead researcher for SPICE operations at the Institute of Space Disaster Physics in Orsay, France.
Other images of the spacecraft show an additional promise for later in the mission when Solar Orbiter is closer to the sun.
The Solar and Heliospheric Imager (SoloHI), led by Russell Howard of the Naval Research Laboratory in Washington, DC, unveiled the so-called zodiac light, sunlight reflected from interplanetary dust – a light as weak as the bright face of the sun obscuring it usually. To see it, SoloHI had to reduce sunlight to a trillionth of its original brightness.
"The images created such a perfect zodiac light pattern that it is so clean. It gives us a lot of confidence that we can see solar wind structures as we approach the sun," said Howard.
Images of the Polar and Helioseismic Imager (PHI) showed that it is also prepared for later observations. PHI maps the magnetic field of the sun, with the focus on the poles.
It will have its heyday later in the mission when the Solar Orbiter gradually inclines its orbit to 24 degrees above the plane of the planet, providing an unprecedented view of the sun's poles.
"The magnetic structures that we see on the visible surface show that PHI receives data of the highest quality," said Sami Solanki, main researcher at PHI at the Max Planck Institute for Solar System Research in Göttingen.
"We are prepared for great science when more poles of the sun come into view," added Solanki.
Today's release highlights Solar Orbiter's imagers, but the mission's four in-situ instruments also showed initial results.
In-situ instruments measure the space environment that immediately surrounds the spaceship. The Solar Wind Analyzer (SWA instrument) shared the first special measurements of heavy ions (carbon, oxygen, silicon, iron and others) in the solar wind from the inner heliosphere.