Solar Orbiter Beams Back Its First Images of the Sun

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Solar Orbiter, a space mission of international collaboration between ESA and NASA, made its first close approach to the Sun in mid-June and captured unique views of the surface of our star.

A high-resolution image from the Extreme Ultraviolet Imager (EUI) on Solar Orbiter, taken with the HRIEUV telescope on May 30, 2020. The circle in the lower left corner indicates the size of Earth for scale. The arrow points to one of the ubiquitous features of the solar surface, called ‘campfires’ and revealed for the first time by these images. On May 30, Solar Orbiter was roughly halfway between the Earth and the Sun, meaning that it was closer to the Sun than any other solar telescope has ever been before. Image credit: ESA / NASA / Solar Orbiter / EUI Team / CSL / IAS / MPS / PMOD / WRC / ROB / UCL / MSSL.

“These are only the first images and we can already see interesting new phenomena,” said Solar Orbiter project scientist Dr. Daniel Müller, of ESA.

“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.”

“These unprecedented pictures of the Sun are the closest we have ever obtained,” added Dr. Holly Gilbert, a project scientist for the mission at NASA’s Goddard Space Flight Center.

“These amazing images will help scientists piece together the Sun’s atmospheric layers, which is important for understanding how it drives space weather near the Earth and throughout the Solar System.”

Launched on February 10, 2020, Solar Orbiter carries six remote-sensing instruments that image the Sun and its surroundings, and four in situ instruments that monitor the environment around the spacecraft.

Normally, the first images from a spacecraft confirm the instruments are working; scientists don’t expect new discoveries from them.

But Solar Orbiter’s Extreme Ultraviolet Imager (EUI) returned data hinting at solar features never observed in such detail. At that time, the spacecraft was only 77 million km away from the Sun, about half the distance between Earth and the star.

EUI principal investigator Dr. David Berghmans from Royal Observatory of Belgium points out what he calls ‘campfires’ dotting the Sun in the new images.

“The campfires are little relatives of the solar flares that we can observe from Earth, million or billion times smaller,” Dr. Berghmans said.

“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 researchers 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.

“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,” said EUI co-principal investigator Dr. Frédéric Auchère, of the Institut d’Astrophysique Spatiale.

“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 Solar Orbiter deputy project scientist Dr. Yannis Zouganelis, of ESA.

This infographic summarizes the first views obtained by the Solar Orbiter mission of the Sun’s outer atmosphere, or corona, and beyond. The corona extends millions of kilometers into outer space and is thought to be the origin of the solar wind, stream of charged particles constantly released by the Sun. On the left, a composite mosaic of first-light images obtained with the Heliospheric Imager (SoloHI) on June 5, 2020, shows the faint signal from electrons in the solar wind at distances from the Sun of about 10 to 85 times the solar radius. On the right, an image obtained on June 21 with Solar Orbiter’s Coronagraph (Metis) provides a view of the corona in visible light, covering heights from 3.2 to 5.8 times the solar radius from the Sun’s center; in the middle of the Metis image, a view obtained with the Extreme Ultraviolet Imager (EUI) on Solar Orbiter shows the Sun’s atmosphere underneath the corona. Image credit: ESA / NASA / Solar Orbiter / SoloHI Team / Metis Team / EUI Team.

This infographic summarizes the first views obtained by the Solar Orbiter mission of the Sun’s outer atmosphere, or corona, and beyond. The corona extends millions of kilometers into outer space and is thought to be the origin of the solar wind, stream of charged particles constantly released by the Sun. On the left, a composite mosaic of first-light images obtained with the Heliospheric Imager (SoloHI) on June 5, 2020, shows the faint signal from electrons in the solar wind at distances from the Sun of about 10 to 85 times the solar radius. On the right, an image obtained on June 21 with Solar Orbiter’s Coronagraph (Metis) provides a view of the corona in visible light, covering heights from 3.2 to 5.8 times the solar radius from the Sun’s center; in the middle of the Metis image, a view obtained with the Extreme Ultraviolet Imager (EUI) on Solar Orbiter shows the Sun’s atmosphere underneath the corona. Image credit: ESA / NASA / Solar Orbiter / SoloHI Team / Metis Team / EUI Team.

Solar Orbiter’s Polarimetric and Helioseismic Imager (PHI) 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,” said PHI principal investigator Dr. Sami Solanki, director of the Max Planck Institute for Solar System Research.

“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,
” said PHI co-principal investigator Dr. Jose Carlos del Toro Iniesta, from the Instituto de Astrofísica de Andalucía.

ESA’s Solar Orbiter carries a suite of ten instruments that work together to provide a coherent picture of solar activity and how that propagates into the wider Solar System, including particles that flow out into the Solar System as the solar wind. To study these phenomena, the instruments are grouped into two families: the in situ instruments and the remote-sensing instruments. This graphic summarizes the first images and data gathered by all instruments as the mission completed its commissioning phase. These include some of the instrument first light images, obtained between May and June 2020. The remote-sensing instruments look directly at the Sun, or slightly to one side to see the Sun’s surface and its outer atmosphere, the corona, while the in situ instruments measure the solar wind as it flows around the spacecraft. The Extreme Ultraviolet Imager (EUI) provides images of the transition from the lower part of the Sun’s atmosphere to the base of the solar corona. The Metis coronagraph blocks the light from the solar surface, so that the fainter outer atmosphere of the Sun, the corona, can be seen. The Solar Wind Analyser (SWA) characterizes the main properties of the solar wind, including the bulk properties of its particles such as density, velocity, and temperature. The Spectral Imaging of the Coronal Environment (SPICE) instrument studies the corona seen in front of the Sun’s disk. The Energetic Particle Detector (EPD) instrument measures the composition, timing and other properties of energetic particles from solar eruptions. The Magnetometer (MAG) measures the magnetic field in the solar wind as it flows past the spacecraft. The Polarimetric and Helioseismic Imager (PHI) measures the magnetic field at the Sun’s surface and allows the investigation of the Sun’s interior via the technique of helioseismology. The X-ray Spectrometer/Telescope (STIX) studies solar X-ray emissions, which are mainly emitted by accelerated electron particles and solar flares. The Heliospheric Imager (SoloHI) instrument images disturbances in the solar wind allowing giant eruptions known as coronal mass ejections to be tracked as they erupt from the Sun. The Radio and Plasma Waves (RPW) instrument measures magnetic and electric fields to determine the wave motions and their interactions with the charged particles of the solar wind. Image credit: ESA / NASA / Solar Orbiter.

ESA’s Solar Orbiter carries a suite of ten instruments that work together to provide a coherent picture of solar activity and how that propagates into the wider Solar System, including particles that flow out into the Solar System as the solar wind. To study these phenomena, the instruments are grouped into two families: the in situ instruments and the remote-sensing instruments. This graphic summarizes the first images and data gathered by all instruments as the mission completed its commissioning phase. These include some of the instrument first light images, obtained between May and June 2020. The remote-sensing instruments look directly at the Sun, or slightly to one side to see the Sun’s surface and its outer atmosphere, the corona, while the in situ instruments measure the solar wind as it flows around the spacecraft. The Extreme Ultraviolet Imager (EUI) provides images of the transition from the lower part of the Sun’s atmosphere to the base of the solar corona. The Metis coronagraph blocks the light from the solar surface, so that the fainter outer atmosphere of the Sun, the corona, can be seen. The Solar Wind Analyser (SWA) characterizes the main properties of the solar wind, including the bulk properties of its particles such as density, velocity, and temperature. The Spectral Imaging of the Coronal Environment (SPICE) instrument studies the corona seen in front of the Sun’s disk. The Energetic Particle Detector (EPD) instrument measures the composition, timing and other properties of energetic particles from solar eruptions. The Magnetometer (MAG) measures the magnetic field in the solar wind as it flows past the spacecraft. The Polarimetric and Helioseismic Imager (PHI) measures the magnetic field at the Sun’s surface and allows the investigation of the Sun’s interior via the technique of helioseismology. The X-ray Spectrometer/Telescope (STIX) studies solar X-ray emissions, which are mainly emitted by accelerated electron particles and solar flares. The Heliospheric Imager (SoloHI) instrument images disturbances in the solar wind allowing giant eruptions known as coronal mass ejections to be tracked as they erupt from the Sun. The Radio and Plasma Waves (RPW) instrument measures magnetic and electric fields to determine the wave motions and their interactions with the charged particles of the solar wind. Image credit: ESA / NASA / Solar Orbiter.

The four in situ instruments on Solar Orbiter then characterize the magnetic field lines and solar wind as it passes the spacecraft.

“Using this information, we 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,” said Solar Wind Analyser principal investigator Dr. Christopher Owen, of the University College London Mullard Space Science Laboratory.

“We are all really excited about these first images — but this is just the beginning,” Dr. Müller said.

“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.”

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This article is based on press-releases provided by the European Space Agency and the National Aeronautics and Space Administration.

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