For the first time, astronomers have mapped the emissions produced when the solar wind meets the magnetic bubble that protects our solar system.
The solar wind is a constant stream of charged particles, mainly protons and electrons, but also heavier ions like carbon and oxygen. When these ions encounter neutral atoms in the upper atmosphere or heliosphere, they capture an electron, causing the emission of soft X-rays. These are the rays detected by the eROSITA telescope.
Separation of the soft X-ray background emission (right) from the cosmic X-ray sky (left) for the western Galactic hemisphere.
The streak patterns visible in the soft X-ray image result from variations in the foreground emission combined with eROSITA's scanning geometry.
These emissions were previously perceived as an annoying interference for studying distant objects. The new detailed map of soft X-rays reveals a close proximity of these interferences. The temporal fluctuations in this radiation prompted scientists to search for a local source, within our own solar system, much closer than the distant emissions from galactic structures, which are constant.
The eROSITA telescope, installed at the L2 Lagrange point about 932,000 miles (1.5 million km) from Earth, observed the sky between 2019 and 2021. Four complete scans allowed the collection of data needed for this mapping. Thanks to this stable position, it was able to isolate emissions from our own solar system from more distant cosmic signals.
The team, led by Gabriele Ponti and Konrad Dennerl, concluded that the fluctuations in the diffuse radiation could not come from distant galactic structures. They were linked to the charge exchange of the solar wind. By separating this local component, the researchers were able to reconstruct an unaltered image of deep emissions and obtain valuable information about the solar wind itself.
This research also indicates that the intensity of the solar wind follows the Sun's activity cycle. It weakens during periods of solar minimum and increases during activity peaks. According to Ponti, what was once an obstacle has now become a valuable tool for heliophysics. The results were published in the journal
Science on April 16.