“We believe the gas trail was produced by the radiation from a white dwarf or some other low-luminosity source zipping through the local interstellar medium and leaving behind an ionized wake,” McCullough said. “The problem is that we have not yet identified the source.”

The filament is roughly Y-shaped. The vertical segment of the Y is about 1.2 degrees long and about 20 arcseconds wide. The full width of the two diagonal segments is about 5 arcminutes. The distance to the gas trail is not known, but it is suspected to be approximately 300 light-years from Earth.

If that turns out to be the case, astronomers might locate other such trails by photographing candidate white dwarfs whose distance and direction of motion are accurately known. 

The object was first photographed in January 1997 with a small camera equipped with a hydrogen-alpha filter. 

Additional observations were made in April and May 1999 with a different filter mounted on the UI’s 40-inch reflecting telescope at Mount Laguna Observatory in southern California. 

The researchers also detected the object with the Wisconsin Hydrogen-Alpha Mapper (WHAM), confirming that the source was not from beyond our galaxy. The research was funded in part by the National Science Foundation.

If the source can be identified and studied, astronomers could use its properties to probe interesting parameters of the local interstellar medium - such as the density of the ambient gas and the level of turbulence in interstellar space. 

“The culprit could be sitting right under our noses and we don’t recognize it,” McCullough said. Additional observations with other telescopes may solve this cosmic whodunit.