Solar Orbiter spacecraft sees the Sun through three different lenses

The ESA-led Solar Orbiter mission is currently observing and studying the Sun with six different imaging instruments, allowing the spacecraft to peel away the Sun’s many layers and reveal its diverse faces.

High-resolution views of the Sun

Recently, the mission released the highest-resolution full views to date of the Sun’s visible surface, known as the photosphere. 

The images were assembled from data captured by the spacecraft’s Polarimetric and Helioseismic Imager (PHI). 

This instrument not only photographs the Sun in visible light but also measures the direction of the magnetic field and maps the speed and direction in which different parts of the surface are moving.

PHI’s measurements of the photosphere can be directly compared to a new image of the Sun’s outer atmosphere, the corona. 

This image is essentially a mosaic assembled from high-resolution images taken by the Extreme Ultraviolet Imager (EUI) instrument on the same day in March 2023. The EUI captures images of the Sun in ultraviolet light.

Daniel Müller, Solar Orbiter’s Project Scientist, noted that the Sun’s magnetic field is key to understanding the dynamic nature of our home star from the smallest to the largest scales. 

“These new high-resolution maps from Solar Orbiter’s PHI instrument show the beauty of the Sun’s surface magnetic field and flows in great detail,” said Miller.

“At the same time, they are crucial for inferring the magnetic field in the Sun’s hot corona, which our EUI instrument is imaging.” 

The image release builds upon one from two years ago when the mission shared full images of the Sun taken by the spacecraft’s EUI and Spectral Imaging of the Coronal Environment (SPICE) instruments on March 7, 2022.

Sunspots and a chaotic magnetic field

Zooming into PHI’s detailed visible light images reveals the Sun’s “surface” for what it truly is: a constantly moving layer of glowing, hot plasma (charged gas).

This layer emits almost all the Sun’s radiation and has a temperature between 4,500 and 6,000°C. 

Beneath it lies the convection zone, where hot, dense plasma churns similarly to magma in Earth’s mantle. This turbulent movement gives the Sun’s surface its grainy appearance.

The most striking features in the images are the sunspots. In the visible light images, these appear as dark spots or holes on the otherwise smooth surface. Sunspots are cooler than their surroundings, emitting less light as a result.

PHI’s magnetic map, or “magnetogram,” shows that the Sun’s magnetic field is concentrated in the sunspot regions, pointing either outward (red) or inward (blue) where the sunspots lie. 

The strong magnetic field explains why plasma inside sunspots is cooler. Normally, convection moves heat from inside the Sun to its surface, but this process is disrupted as charged particles are forced to follow the dense magnetic field lines in and around the sunspots.

Mapping movement on the surface

The speed and direction of material movement on the Sun’s surface are displayed in PHI’s velocity map, also known as a “tachogram.” 

In this map, blue indicates movement toward the spacecraft, while red signifies movement away. The map reveals that while the plasma on the Sun’s surface generally rotates with the Sun’s overall spin around its axis, it is pushed outward around the sunspots.

Finally, EUI’s image of the Sun’s corona shows what happens above the photosphere. Above the active sunspot regions, glowing plasma protrudes outward.

This million-degree plasma follows magnetic field lines extending from the Sun, often connecting neighboring sunspots.

Piecing together the Sun’s mosaic

The images were captured when the Solar Orbiter was less than 74 million kilometers from the Sun. 

Being so close meant that each high-resolution image taken by PHI and EUI covered only a small portion of the Sun. To image the entire face, the spacecraft had to be tilted and rotated after each individual image was taken.

To create the full-disc images presented, all individual images were stitched together like a mosaic. Both the PHI and EUI mosaics consist of 25 images each, captured over more than four hours. 

The resulting mosaics have a diameter of nearly 8,000 pixels, revealing an astonishing amount of detail.

The image processing required to produce the PHI mosaics was new and challenging.

Now that it has been accomplished once, future data processing and mosaic assembly will be faster. The PHI team expects to provide such high-resolution mosaics twice a year.

Advancing our understanding of the Sun

The new images not only showcase the beauty of our star but also enhance our understanding of its complex magnetic fields and dynamic processes. 

By comparing data from different instruments, scientists can gain deeper insights into how the Sun’s magnetic field influences phenomena from the smallest to the largest scales.

With continued efforts from missions like Solar Orbiter, we are peeling back the layers of the Sun to better comprehend its impact on our Solar System.

Video/ Image Credit: European Space Agency 

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–