Astronomers Have Discovered a ‘Tunnel’ of Hot Gases Extending Out From Our Region of Space

Astronomers with Germany’s Max Planck Institute of Extraterrestrial Physics has discovered a strange interstellar “tunnel” of hot gases that stretches out for hundreds of light years from our region of space, a relatively empty pocket of space that the Sun is currently travelling through, toward the constellation Centaurus.

Estimated to be roughly 1,000 light years across, the Local Hot Bubble (LHB) is a region of space that our Solar System is currently passing through where the sparse particles that make up the interstellar medium (ISM) are spread ten times thinner than what is found in the rest of the Milky Way. The region was blasted out by a series of supernovae that occurred roughly 14.4 million years ago, and although the individual particles are spread too thinly to be able to transfer their heat in any meaningful way, each atom is still has a temperature of around a million degrees Kelvin (or Celsius, if you prefer; when it comes to temperatures that high, it doesn’t matter).

The astronomers’ survey found that, in relation to the galactic plane, the bubble is noticeably taller than it is wide, spreading more upward and downward than side-to-side, a result of there being less pressure in those directions from the collective stellar wind generated by the galaxy’s stars. But in defining the bubble’s layout, shaped by subsequent supernovae over the millions of years since its formation, they also discovered a “tunnel” of this hot, sparse gas extending out toward the constellation of Centaurus.

“What we didn’t know was the existence of an interstellar tunnel towards Centaurus, which carves a gap in the cooler interstellar medium,” explains Michael Freyberg, an astrophysicist with the Max Planck Institute. “This region stands out in stark relief.”

The Centaurus tunnel, as the team is calling it, “may just be a local example of a wider hot ISM network sustained by stellar feedback across the Galaxy,” according to the study’s press release, potentially representing a series of bubbles and tunnels that stretch across the breadth of the Milky Way. The survey also enabled the team to determine roughly when the solar system entered the LHB on its journey around the galaxy.

“Another interesting fact is that the Sun must have entered the LHB a few million years ago, a short time compared to the age of the Sun,” remarked study co-author Gabriele Ponti. “It is purely coincidental that the Sun seems to occupy a relatively central position in the LHB as we continuously move through the Milky Way.”