Researchers may have unlocked the mystery behind the superheated gas surrounding the Milky Way. This enigmatic veil of gas, which has intrigued astronomers for decades, is thought to be sustained by explosive stellar activity within the galaxy’s disc.
The presence of a vast gas reserve, larger in volume than the Milky Way’s stars, is essential for star formation. However, its diffuse nature has made it difficult for astronomers to measure. Recent studies have revealed that the galaxy is enveloped by a massive sphere of gas, reaching temperatures of millions of degrees Kelvin and extending up to 700,000 light-years.
In recent years, scientists discovered even hotter gaseous matter, estimated at a scorching 10 million degrees Kelvin. This gas emits faint X-ray signals, detected in all directions of the galaxy, and absorbs light from distant quasars. The discovery sparked a wave of research to uncover the heat source sustaining this fiery phenomenon.
Scientists at the Raman Research Institute (RRI), along with collaborators from IIT-Palakkad and Ohio State University, have proposed a model explaining the origins of this gas. Their findings, published in the Astrophysical Journal, suggest that the gas emitting X-rays originates from a puffed-up region around the Milky Way’s stellar disc.
Mukesh Singh Bisht, a PhD student at RRI, explained that ongoing star formation within the disc results in massive stars exploding as supernovae, which heat the surrounding gas to extreme temperatures. These explosions not only sustain the heat but also enrich the gas with elements formed in stellar cores, such as sulphur, magnesium, and neon.
This heated gas swirls turbulently around the galaxy, either cooling and returning to the disc or escaping into the surrounding medium. Bisht noted that the X-ray emissions and the absorbing gas detected in quasars are not identical but are linked through these dynamic processes.
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According to Biman Nath, faculty at RRI and co-author of the study, the absorbing gas’s elemental composition further highlights the role of nuclear reactions within stars. “The presence of α-elements, like sulphur and magnesium, confirms that massive stars enrich the gas during supernova explosions,” he said.
The faint X-ray signals generated by this fiery gas could provide deeper insights into the galaxy’s dynamics. The research team plans to explore the phenomenon further by testing their models across different frequencies.
This breakthrough offers a clearer understanding of the Milky Way’s gaseous halo and its role in the galaxy’s evolution, while also opening new avenues for studying the interplay between stars and the surrounding medium.
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