This X-ray image shows our solar system ‘breathing’
When you purchase through links on our articles, Future and its syndication partners may earn a commission.
Illustration of the separation of the SWCX foreground emission from the cosmic X-ray sky, for the Western Galactic Hemisphere. The stripe patterns visible in the SWCX image result from temporal variations in the foreground emission combined with the scanning geometry of eROSITA. | Credit: MPE
Astronomers have, for the first time, spotted the “breath of the solar system”. The discovery comes in the form of X-ray emissions generated when the electrically charged solar wind hits both Earth’s atmosphere and the bubble that surrounds our solar system, the heliosphere.
This phenomenon, known as “solar wind charge exchange”, was observed by the eROSITA space telescope, allowing a team of scientists to create a “soft X-ray” sky map. This X-ray glow is emitted when heavy ions in the solar windlike carbon and oxygen, capture an electron from the neutral atoms of either of our atmosphere or the heliosphere.
Solar wind charge exchange was previously thought to be interference or background noise interfering with astronomers’ attempts to measure plasma density and temperature in distant galaxies and galaxy clusters. By producing the clearest map yet of soft X-rays, this team has further validated the phenomenon as a fascinating area of study in its own right.
Reconstruction of how the diffuse X-ray sky should have appeared at eROSITA from May to October 2021. At any time, eROSITA observed only a 1° wide field in the direction of its scan, indicated by a cyan curve. Each 360° scan lasted 4 hours and was performed approximately perpendicular to the direction of the Sun, which is located in the overexposed moving region. | Credit: K. Dennerl, J. Sanders, H. Brunner and the eSASS team (MPE); E. Churazov, M. Gilfanov (IKI)
Launched by the Russian space agency Roscosmos on July 13, 2019, eROSITA is currently at a gravitationally stable point between Earth and the sun known as Lagrange Point 2. This point, also known simply as L2, is located 932,000 miles (1.5 million kilometers) from Earth. From the L2 vantage point, the X-ray spacecraft was able to collect the data for this X-ray map by scanning the sky four times between 2019 and 2021.
“We wanted to study Milky WayThe X-ray emission, especially the circumgalactic medium, is expected to extend into a large plasma sphere around our galaxy,” team member and Brera Astronomical Observatory astronomer Gabriele Ponti said in a statement translated from Italian. “By analyzing the eROSITA data, we noticed significant and unexpected variations in this diffuse radiation.
“We realized that they could not come from distant galactic structures, which are constant, but must be linked to a phenomenon much closer to us: the charge exchange of the solar wind.”
Team member Konrad Denneri, a researcher at the Max Planck Institute, pointed out that the team was then able to isolate the local component of the radiation, adding: “In this way, we not only reconstructed an unchanged picture of emissions from deep space, but we also obtained valuable information about the solar wind emitted in all directions, as well as its variations over a two-year period.”
Research suggests that the solar wind emitted by the solar system follows fluctuations in the solar cycle, weakening during periods of minimal activity and intensifying during periods of increased solar activity.
“With this work, what was previously an obstacle becomes a powerful diagnostic tool for heliophysics, allowing us to study the components of the solar wind and its interaction with the interstellar medium,” Ponti said. “Understanding how the dynamics of the heliosphere changes the appearance of the sky in X-rays is fundamental to correctly interpreting the hot phase of the Milky Way.”
The team’s research was published April 16 in the journal Science.
