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The iconic Sombrero galaxy, 30 million light-years from Earth, on the border between the constellations Virgo and Corvus, revealed on April 24, 2026, an invisible halo more than three times wider than the visible galaxy itself, captured for the first time by the 570-megapixel Dark Energy Camera installed on the Víctor M. Blanco telescope at the Cerro Tololo Observatory in Chile. According to the official image released by NOIRLab and analyzed by Live Science, the observation also revealed a previously unknown stellar stream, direct evidence of a violent merger with a smaller satellite galaxy in the distant past.
Researchers following the study highlight that the more dark matter they can map around the Sombrero galaxy, the sooner current cosmological models can reveal the true composition of that invisible material that sustains the orderly rotation of billions of stars. The newly detected halo is described as diffuse, faint, and impossible to photograph with amateur or even professional telescopes without the prolonged exposure time and sensitivity of the Dark Energy Camera.
The Sombrero galaxy itself, also cataloged as Messier 104 and NGC 4594, has been known since the 18th century for its almost perfect Mexican hat shape seen almost in profile. The central dark band of interstellar dust contrasts with the bright core, forming one of the most reproduced profiles in astronomy books around the world.
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What the new Dark Energy Camera image shows that Hubble did not see
The Dark Energy Camera, known as DECam, is a 570-megapixel instrument attached to the 4-meter Víctor M. Blanco reflector telescope, in continuous operation in the high Atacama Desert since 2012. Unlike the Hubble Space Telescope, which offers superior resolution in small fields of view, the DECam combines high sensitivity with a wide field, allowing it to simultaneously capture bright and extremely faint structures.
It was precisely this combination that allowed the identification of the gigantic halo and the stellar stream now associated with the Sombrero galaxy. The outermost regions of these structures emit light thousands of times fainter than the galactic core, requiring long exposures and advanced processing algorithms to separate the signal from atmospheric noise.
According to astronomers from the Cerro Tololo consortium, the final image from April 24 results from the sum of several hours of observation, in multiple color filters, calibrated with reference to other already studied galaxies. The result is considered a methodological milestone, paving the way for similar analyses in hundreds of nearby galaxies in the coming years.
Why the invisible halo confirms the dark matter puzzle
Dark matter corresponds, according to current cosmological models, to approximately 27% of all the content in the universe, compared to only 5% of visible common matter and 68% of dark energy. Although invisible and impossible to measure directly, it exerts gravitational attraction on stars, gas, and entire galaxies, sustaining structures that would otherwise disintegrate in accelerated rotation.
Researchers find that the more bright material they can map on the periphery of giant galaxies, the more they can infer the presence and shape of the surrounding dark halo. In the case of the Sombrero, the stellar stream now observed by the DECam acts as a natural tracer of that invisible matter, showing how gravitationally the halo is organized around the galaxy.
According to a study published in the journal Monthly Notices of the Royal Astronomical Society, January 2025 edition, previous observations of the Sombrero with the James Webb Space Telescope already indicated low-luminosity structures around the main disk, but lacked direct confirmation of the extent and shape of the dark halo. The new DECam image fills this gap.
The violent galactic merger that left marks until today
The newly identified stellar stream around the Sombrero galaxy is interpreted by astrophysicists as a direct scar from an ancient collision between the Sombrero and a smaller satellite galaxy. This type of event, known as a galactic merger, is considered one of the main mechanisms for the growth of large galaxies in the observable universe.
During these mergers, which last billions of years, the larger galaxy absorbs stars, gas, and dust from the smaller one, but leaves behind elongated bands of matter, scattered as gravitational trails around the final system. These bands can remain detectable for long cosmological periods, providing an archaeological record of the violent past of galaxies.
According to Universe Magazine, in specialized coverage of the discovery, the study of the Sombrero helps refine models on how many of these mergers have occurred since the beginning of the universe, with direct implications for the rate of star formation and the chemical history of the Milky Way, which has also undergone similar events.
How Brazil indirectly participates in this cosmological mapping
Brazil has been an active member of the Dark Energy Survey project since 2014, with researchers from institutions such as the National Observatory in Rio de Janeiro, the Federal University of Rio Grande do Sul, and the University of São Paulo. The country also participated in the development of software and calibration algorithms used in the analysis of DECam observations over the past decade.
This direct involvement means that part of the advances announced about the Sombrero galaxy involves Brazilian scientific contributions, especially in the image processing phase and data cross-referencing with cosmological simulations. Brazil also maintains a partnership with the Vera Rubin Observatory in Chile, whose full operation in 2026 promises to revolutionize dark matter mapping.
It is worth noting that other discoveries about galactic structures and cosmology frequently appear in our Curiosities and Science sections, connecting astronomical advances to contemporary debates on energy and space technology.
Next steps: the Webb, the Vera Rubin, and the future of dark matter
The James Webb Space Telescope, in operation since 2022, will return to observe the Sombrero galaxy in different infrared ranges throughout 2026 and 2027, aiming to complement DECam data with information on temperature and chemical composition of the detected structures. The first combined observations are expected in 2027.
In parallel, the new Vera Rubin Observatory in Chile will enter full operation in 2026 with the declared goal of photographing the entire visible sky of the southern hemisphere every three nights, producing the largest cosmological catalog ever assembled. Galaxies like the Sombrero will be monitored on an unprecedented statistical scale.
The researchers involved in the study state that this convergence of instruments can significantly accelerate the understanding of the nature of dark matter and the actual speed of the universe’s expansion, two of the greatest puzzles of modern physics. The Sombrero galaxy, known since 1781, has become a key character in this next decade of astronomical discoveries.
On the other hand, experts warn that each new image brings as many answers as new questions, and the case of the Sombrero illustrates this dynamic well. The 2026 data has already raised new questions about the frequency of galactic mergers in lenticular galaxies, and new observations are already scheduled for 2027.
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