In the southern sky, behind a dense veil of dust, hides a source of gamma rays — the most energetic light in the Universe. It shines so brightly that it can be seen even through this veil, but the object itself remains invisible. Astronomers pointed the ALMA radio telescope at the neighboring gas clouds and saw a pattern that gave the invisible object away.
The clouds consist of many thin filaments: each about half a light-year wide and tens of light-years long. All the filaments are aligned along a single axis, like iron filings around a magnet. Such alignment is not random. The filaments stretch for 170 light-years and outline the trail of a pair of giant jets that once blasted from the center of the gamma-ray source.
The jets could have been launched by a black hole or a neutron star — the remnant of a massive star that exploded millions of years ago. This remnant is now hidden by dust, but its past activity is impressive: it accelerated particles for 1–10 million years. For comparison, a supernova explosion accelerates particles for only a few thousand years.
The energy stored in the accelerated particles is colossal — ten times greater than that of the most powerful known supernova remnants. To accumulate that much, a thousand such remnants would be needed. This source is possibly the strongest particle accelerator in the disk of our Galaxy.
The gas filaments seen by ALMA are hundreds of times thinner than they appear: their width is half a light-year, and their length is up to twenty light-years. If you scaled such a filament down to the thickness of a human hair, its length would be like a football field.