Mysterious Filaments of Giant Galaxy M87 Captured from La Palma’s Summit

An international study released by the Instituto de Astrofísica de Canarias provides the most complete image yet of the filamentary structures surrounding M87—a colossal galaxy located “only” 55 million light‑years from Earth—capturing the enigmatic filaments generated by its super‑massive black hole.

A New, Unprecedented View

An international team of astronomers has produced the most detailed and comprehensive image to date of the mysterious filaments that envelop the giant elliptical galaxy M87. The observations were carried out with the Gran Telescopio Canarias (GTC, also known as Grantecan) on the summit of La Palma, within the Roque de los Muchachos Observatory, and complemented by data from the Canada‑France‑Hawaii Telescope (CFHT). The study reveals how these long, thread‑like structures move, evolve, and interact both with the surrounding galactic environment and with the activity of the central super‑massive black hole.

The findings were published in Monthly Notices of the Royal Astronomical Society.

M87: A Giant Galaxy and Its Mysterious Threads

M87 lies roughly 55 million light‑years away and is a super‑giant elliptical galaxy famous for its extremely active super‑massive black hole (SMBH). This 6.5‑billion‑solar‑mass engine, made world‑wide headlines after the Event Horizon Telescope captured the first image of its shadow, powers relativistic jets of high‑energy particles that extend far beyond the galaxy and are most striking in radio wavelengths. The jets’ intensity varies with the amount of material the black hole accretes, alternating between highly active and quieter phases.

Even during quieter periods, the jets play a crucial role in shaping both the galaxy itself and the hot intracluster gas that surrounds it. M87 sits at the heart of the Virgo Cluster, a massive assembly of thousands of galaxies immersed in a diffuse, hot intracluster medium reaching tens of millions of degrees. Like many central cluster galaxies, M87 is threaded by a complex network of long, thin filaments that stretch far from its core. After decades of study, their origin remains puzzling:

Where do they come from?
How can such delicate structures survive in such a hostile environment?
To what extent are they linked to the black‑hole activity, as many astronomers suspect?

“M87 is the nearest galaxy known to host this kind of filamentary structure,” explains Camille Poitras, lead author of the study and a master’s student at Université Laval (Quebec, Canada). “It is probably one of the few where the filaments extend so far from the centre that they appear almost detached, ‘floating’ beyond the galaxy.”

Observations and Instruments

To build a detailed portrait of the filaments, the team combined two complementary data sets:

MEGARA on the GTC – targeted two distinct regions: (1) complex filaments near the core, close to the current jets, and (2) much more distant filaments lying beyond the main body of the galaxy in a relatively tranquil environment.
SITELLE on the CFHT – provided a panoramic view of the entire filament network.

Together, these observations deliver the most complete picture of M87’s filaments to date, revealing their motions, composition, and connections to the surrounding medium.

Turbulent Inner Filaments

Previous work already showed that filaments near the centre are highly turbulent and chaotic, constantly disturbed by the powerful jets. The high spatial resolution of MEGARA uncovered additional, smaller‑scale agitation, likely driven by Type Ia supernova explosions from old stellar populations that are widespread throughout the galaxy.

“MEGARA’s ability to deliver spatially resolved information on these filaments, combined with the sensitivity of a telescope like the GTC, has been essential for probing such subtle structures,” says Antonio Cabrera Lavers, scientific operations manager of the GTC.

Quieter Outer Filaments

Further out, the picture changes dramatically. A detached outer filament moves in a more stable, uniform fashion, and its presence appears linked to a past jet episode from an earlier active phase. Gas composition also varies:

Inner filaments – heavily influenced by the SMBH and its active jets, showing distinct chemical signatures.
Outer filaments – despite residing in a calmer region, exhibit unexpected chemical properties, hinting at underlying processes that are not yet fully understood.

“These new observations have helped us determine how M87’s black‑hole outflows shape and energize the filaments,” explains Marie‑Lou Gendron‑Marsolais, associate professor at Université Laval and co‑author of the paper. “They are ‘live’ evidence of how the black hole impacts the galaxy, even far from its nucleus.”

Implications and Future Work

The results demonstrate that the filaments are tightly coupled to both the current and past activity of M87’s super‑massive black hole. A combination of mechanisms—relativistic jets, stellar explosions, and interactions between hot and cold gas—appear to work together to sculpt and move these delicate structures.

Understanding how these processes intertwine remains a challenge. Upcoming high‑resolution observations and innovative analysis techniques will be crucial for uncovering how the filaments form, survive, and evolve over cosmic time.

Original article: Camille Poitras and Marie‑Lou Gendron‑Marsolais, “Observations of AGN‑driven feedback: dynamics and ionization of the filaments in M87”, MNRAS, 2025.