English (UK)
An international team led by astronomers from the University of Jaén (Spain) has found the object, hidden behind a cloud of interstellar dust about 12,000 light-years from Earth. The discovery was made after analysing a large dataset across various wavelengths, including spectra taken at Calar Alto. This first confirmed microblazar in the Milky Way consists of a star with a black hole orbiting it that triggers a jet of matter -at speeds close to the speed of light- almost directly toward our planet. Its opposite, invisible jet collides with a gas cloud and could be the source of some of the most energetic particles ever detected in the universe.
For thirty years, astronomers have been searching for something they were pretty certain must exist in the Milky Way, but they had not yet found it. Now, an international team (from Spain, the Netherlands, and Argentina), led by astronomers from the University of Jaén (Andalusia), has located it after a long investigation, hidden behind a large cloud of interstellar dust, about 12,000 light-years from Earth.
The object is called IRAS 18293−0941. It is a binary system: a hot, massive star around which a black hole orbits every little more than eleven days (11.38, to be precise). Material from the star falls toward the black hole, which swallows part of it and ejects the rest along two opposing, ultra-fast jets (traveling at three-quarters the speed of light). What makes this system remarkable is the direction in which those jets are pointing: almost directly at us.
Black holes with jets pointing toward Earth are not a novelty in astronomy. At the centers of very distant galaxies, supermassive black holes (billions of times more massive than the Sun) emit jets that, by chance, point in our direction. These objects are called “blazars” and are extraordinarily bright and violent.
Since the 1990s, theoretical studies have argued that the same phenomenon should occur on a smaller scale within our own Galaxy, and they dubbed them “microblazars”. But no one had ever found one that could withstand close scrutiny. IRAS 18293−0941 is the first to do so.
“Everything in IRAS 18293−0941 was hidden in plain sight,” explains Josep Martí Ribas, a full professor at the University of Jaén (UJA) and co-author of the study alongside Pedro Luque Escamilla, also a full professor at UJA. “It is hidden behind so much dust that it is practically invisible in standard optical images. It was catalogued decades ago and then was more or less forgotten,” the researcher notes.
A jet pointing toward us
After years of monitoring using data collected in the visible spectrum—with notable Spanish participation from the Calar Alto (in the Andalusian Sierra de los Filabres) and Montsec observatories (in the Catalan Pyrenees), as well as the University of Jaén telescope—it was found that the star’s light flickered subtly: a hint of variation that revealed an 11.38-day orbit and the fact that this orbit was being observed almost edge-on.
Several spectra obtained with the CAFOS instrument on the 2.2-meter telescope have provided two additional clues: “On the one hand, the persistence of the single-peaked Halpha emission line is confirmed, which is what is expected in a microblazar,” notes Martí Ribas, adding that “on the other hand, the CAFOS spectrum reveals P-Cygni profiles in some lines, confirming the presence of a significant circumstellar envelope surrounding the system.”
In radio waves, “the images revealed the existence of a jet pointing toward us: a single jet, on one side only, which could only be explained if it were indeed pointed almost directly toward Earth,” Josep Martí Ribas also explains. The jet on the opposite side remains hidden due to a prediction of Einstein’s Theory of Relativity. Thus, using the European VLBI Network (EVN)—a network of radio telescopes spread across the Old Continent, including the Yebes telescope (Guadalajara, Spain), which acts as a single antenna thousands of kilometers in diameter—extremely high-resolution radio wave maps were obtained that confirmed the jet’s orientation and that it did indeed originate from the binary star system.“That was the moment when the result became solid,” notes Benito Marcote (Joint Institute for VLBI ERIC, JIVE, Netherlands). A one-sided radio jet could always have originated from a distant galaxy that happened to lie in the same direction as the star we were studying. “The resolution achieved by the EVN data, combined with the star’s known position from the Gaia satellite, confirmed it: the jet truly belongs to the star system,” explains Benito Marcote.
The other jet—the one moving away—is invisible. But it doesn’t simply vanish, and the team detected its effects. In this regard, detailed images from “MeerKAT,” the South African radio observatory, show that there is a massive bubble (about 100 light-years in size) that the jet has carved out in the interstellar medium. And at the farthest edge of that bubble lies a bright, compact point: a “hot spot.” A collision—a clash between the jet and the interstellar medium—where particles are accelerated, dust is heated, and hydrogen gas is made to glow.At that exact location, high-energy observatories such as LHAASO (China), HAWC (Mexico), H.E.S.S. (Namibia), and the Fermi satellite have detected a source of ultra-high-energy gamma rays: individual photons carrying more than 100 trillion electronvolts (100 TeV)—more than ten times the energy that the Large Hadron Collider (LHC, in Geneva) can impart to a single proton. Where these Galactic “PeVatrons” (one petaelectronvolt is equal to 1,000 TeV) get their energy is one of the open questions in modern astrophysics.The study led by the two professors from University of Jaén details how the pieces might fit together: the jet carries enough energy (half a million times the energy radiated by the Sun) so that, where it strikes the molecular cloud, it accelerates protons to enormous energies, which then collide with the dense gas. These collisions produce particles that immediately begin to shine, emitting gamma rays. “The elegant thing is that the accelerating engine and the target are two distinct objects, separated by tens of light-years,” says UJA professor Pedro Luque Escamilla.
In this regard, for the first time, we have an analog of distant blazars right around the corner, confirming a prediction made thirty years ago. This opens a window to explore these types of systems in much greater detail and to track their evolution on human timescales. Furthermore, the interaction of its jet with the interstellar medium confirms that these interactions can be important when studying how our Galaxy evolves. Finally, the possible association with a “PeVatron” region brings us one step closer to understanding these extreme regions and their origin.The team is already working on several fronts: repeated high-resolution observations to try to capture the evolution of the jet and to see even deeper into the system; a more detailed study of the molecular cloud and its interaction with the jet, to uncover the processes taking place in those areas; and the ongoing search for new systems of this type in our galaxy, the Milky Way.
PUBLICATION
J. Martí, P. L. Luque-Escamilla, B. Marcote, et al. (2026), ‘A Galactic microblazar as a potential accelerator of ultra-high-energy particles’, Astronomy & Astrophysics, in press
CONTACTS
Universidad de Jaén (UJA) Josep Martí jmarti @ ujaen.es
Observatorio de Calar Alto (CAHA) Gilles Bergond gbergond @ caha.es
COMMUNICATION – OBSERVATORIO DE CALAR ALTO
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