Mystery of Milky Way's Fiery Gas Veil Solved by Scientists

For decades, astronomers have been intrigued by the discovery of a massive sphere of hot gas surrounding the Milky Way. Extending up to 700,000 light-years from the galactic disc, this gaseous halo, reaching temperatures of several million degrees Kelvin, has been a topic of extensive research. However, recent studies have uncovered an even hotter component of this gas—measuring a staggering 10 million degrees Kelvin—emitting faint X-rays and absorbing light from distant quasars.

This new revelation raised a puzzling question: what powers and sustains this fiery gas around the Milky Way? In a breakthrough, scientists have now traced its origins to supernova explosions and the turbulent processes associated with ongoing star formation across the galaxy.

Milky Way's Superheated Gas Halo: A Breakthrough Discover

Research teams from the Raman Research Institute (RRI), in collaboration with IIT-Palakkad and Ohio State University, have proposed a model explaining the origins of this fiery gas. Published in the Astrophysical Journal, the findings suggest that the gas responsible for emitting X-rays and the gas absorbing light from quasars are distinct in nature.

According to the model, massive stars forming in the Milky Way’s disc explode as supernovae, releasing immense energy. These stellar explosions heat the surrounding gas to extreme temperatures, creating the X-ray-emitting halo observed by astronomers. At the same time, the supernovae enrich the gas with heavy elements such as sulfur, magnesium, and neon, produced during nuclear reactions in the stars’ cores.

"Supernova explosions not only heat the gas but also inject elements synthesized within the massive stars into the surrounding environment," explained Dr. Biman Nath, a faculty member at RRI.

Milky Way's Hot Gas Halo Explained: A Stellar Phenomenon

The research identifies two distinct components of the hot gas:

1. X-ray Emitting Gas:
   This component forms a turbulent, puffed-up region around the Milky Way’s disc. The continuous star formation across the galaxy ensures a steady supply of supernovae, which, in turn, heat this gas to temperatures of 10 million degrees Kelvin. Some of this heated gas escapes into intergalactic space, while the rest cools and eventually falls back onto the disc, fueling further star formation.

2. Absorbing Gas:
   This component was identified through light absorption patterns in the spectra of distant quasars. Enriched with α-elements (such as sulfur, magnesium, and neon, whose nuclei are multiples of helium nuclei), this gas hints at violent supernovae events occurring outside the galactic disc.

"Runaway stars ejected from the disc can explode as supernovae in the galactic halo, producing localized puffs of fiery, α-element-rich gas," added Mukesh Singh Bisht, a PhD student at RRI. "When these gas clouds align with the light from quasars, they absorb specific wavelengths, creating shadow signals."

Future Implications of Discovery 

The faint X-ray signals from this fiery gas provide a unique window into the dynamic processes shaping the Milky Way’s structure. The study also highlights the role of supernovae and star formation in enriching the galaxy’s environment with heavy elements essential for planet and life formation.

The research team plans to test their models further by studying the gas at other frequencies, potentially uncovering more clues about the mechanisms behind this superheated halo.

A Glimpse Into the Cosmos

This discovery marks a significant step in understanding the Milky Way’s evolution. The interplay of star formation, supernovae, and turbulent gas flows offers valuable insights into the galaxy’s lifecycle and its connection to the broader universe.

The fiery veil surrounding the Milky Way, long a cosmic enigma, is now better understood, thanks to the persistent efforts of scientists. This discovery not only unravels the mystery of the gas but also paints a vivid picture of the violent and dynamic processes that shape our galaxy.