A long, narrow filament of gas and dust has been identified within the Milky Way, stretching over 300 light-years while remaining only a few light-years wide. Nicknamed “Nessie”, the structure may represent a key element in tracing the galaxy’s internal framework.
Astronomers have long struggled to map the Milky Way from within, where perspective limits large-scale observation. Structures like this one provide rare reference points that can help outline the galaxy’s spiral architecture.
The finding was presented by Alyssa Goodman of the Harvard-Smithsonian Center for Astrophysics during a meeting of the American Astronomical Society, drawing on earlier infrared observations and updated analysis of known data.
A Filament Both Vast And Extremely Thin
The identified structure extends for more than 300 light-years but measures just 1 to 2 light-years across. As stated by Alyssa Goodman, this extreme proportion makes it resemble a long, slender bone rather than a thicker formation, a comparison she used to illustrate its unusual shape.
“This is the first time we’ve seen such a delicate piece of the galactic skeleton,” she said. “This bone is much more like a fibula — the long skinny bone in your leg — than it is like the tibia, or big thick leg bone.”
Infrared view of “Nessie”, a thin, elongated filament in the Milky Way. Credit: NASA/JPL/SSC
The filament contains material equivalent to around 100,000 suns. As stated by the research presented in arXiv, this mass is concentrated along a remarkably narrow line within the galactic plane, giving the structure its distinctive appearance.
A Structure Far Longer Than First Observed
The feature known as Nessie was initially detected in 2010 through data collected by NASA’s Spitzer Space Telescope. At that time, only its central section had been identified. Based on the latest study, the structure may be up to eight times longer than previously thought.
This revised measurement alters the interpretation of the feature. As reported during the American Astronomical Society meeting, what seemed to be a localized filament is now understood as part of a much more extended and coherent structure.
NASA’s Spitzer Space Telescope. Credit: NASA/JPL-Caltech
Mapping The Milky Way in Three Dimensions
Determining the structure of the Milky Way is particularly complex due to our position inside it. Alyssa Goodman pointed out that filaments like Nessie could lie along spiral arms or connect larger galactic features, acting as structural markers.
“The very long and thin infrared dark cloud “Nessie” is even longer than previously thought, and its galactic position suggests that it lies directly in the Milky Way’s mid-plane, tracing a highly elongated, bone-like feature within the prominent Scutum-Centaurus spiral arm,” wrote the authors.
Schematic map of the Milky Way showing its spiral arms, with the Sun’s position marked and major structures. Credit: Researchgate
Simulations of spiral galaxies have predicted such networks of filaments, and similar formations have been observed in other galaxies. As they noted, locating further “bone”-like features could allow astronomers to build a more precise 3D map of the Milky Way and better grasp its structure.