A microblazar is a stellar-mass black hole that fires a jet almost straight at us, and until this year no one had pinned one down in the Milky Way. Astronomers predicted such objects about thirty years ago. On September 22, 2026, a team led by Josep Martí of the University of Jaén announced a strong candidate, a binary system called IRAS 18293-0941, and argued that its jet may be accelerating particles to extraordinary energies.

The work was posted to arXiv on September 1 as “A Galactic microblazar as a potential accelerator of ultra-high-energy particles” and, according to EarthSky’s account of the announcement, has been accepted by Astronomy & Astrophysics. The word “candidate” and the word “potential” in that title are both doing real work.

What makes the object interesting is the combination of a geometry that explains why it hid for so long and a nearby gamma-ray source that hints at a larger role. This post lays out how the source was identified, what the numbers are, why a single visible jet is not surprising, and which parts of the story are still conjecture.

Blazars, Microquasars and the Missing Middle

A blazar is a galaxy whose central supermassive black hole launches a jet pointed close to our line of sight, which makes it blindingly bright. A microquasar is the small-scale version: a black hole or neutron star pulling gas from a companion star and launching jets of its own. Put the two ideas together and the result is a microquasar viewed down the barrel of its jet.

Catalogues of Galactic X-ray binaries include plenty of microquasars. A confirmed microblazar was missing, and the reason is partly practical. Dust in the Galactic plane hides many sources in ordinary optical images, and a jet pointing at us is viewed end-on, so it looks short and compact.

How IRAS 18293-0941 Was Pinned Down

The infrared satellite IRAS first detected the object in 1983, per ZME Science’s report, and it sat in catalogues for decades afterward. The new identification combines several kinds of data.

Dense star field toward the Milky Way center crossed by dark dust lanes
  • Radio imaging. The European VLBI Network, a continent-spanning array of radio telescopes, resolved a bright, narrow radio structure extending from only one side of the source.
  • Position match. The European Space Agency’s Gaia satellite measured the position of the star, and the radio jet lined up with it. A lopsided radio source alone could be a background galaxy, so this match is what ties the jet to the stellar system.
  • Optical timing. Optical observations revealed an orbital period of 11.38 days, with small brightness variations that suggest we see the orbit nearly face-on.
  • A larger structure. MeerKAT radio data in South Africa suggest the receding jet has carved a bubble roughly 100 light-years from the black hole, and that it strikes a dense cloud of gas and dust.

The reported properties are a distance of about 12,000 light-years, a jet speed near three-quarters of the speed of light, and a black hole estimated at roughly ten times the mass of the Sun. EarthSky’s report contains an internal inconsistency on distance, since its image caption refers to tens of thousands of light-years, so that figure deserves checking against the paper.

The abstract adds two modelling statements. The system shows no rapid variability, which the authors suggest could be smoothed out by a dense circumstellar envelope. And their physical model supports a likely link to LHAASO J1831-1007u*, an ultra-high-energy gamma-ray source nearby.

Why the Gaia Match Carries the Argument

A one-sided radio jet is not unusual in itself. Distant galaxies with jets aimed our way are common, and one of them lying far behind a Galactic star would produce a similar picture. That is why the positional match with Gaia matters so much. Radio interferometry of this kind locates a source to milliarcsecond-level precision (background knowledge), and Gaia pins the star to a comparable level, so the two coincide only if the jet belongs to the stellar system.

The orbital period supplies a second tie. A binary orbit of 11.38 days is a property of the stellar system, and the optical data carry that signal. When the radio jet and the periodic star share a position, the case that both belong to a single object is hard to avoid, though the paper’s own significance estimate for the match was not in the material I retrieved.

Why One Jet Looks Like the Only Jet

A black hole system launches two jets in opposite directions. Only one is seen directly here, and relativistic beaming explains why. Matter moving at a large fraction of the speed of light has its emission boosted when it approaches the observer and dimmed when it recedes.

Array of water tank detectors on a high desert plateau at dusk

A standard estimate for the brightness ratio of an approaching jet to its twin is ((1 + β cos θ)/(1 − β cos θ)) raised to a power of about 2 for a continuous jet, where β is the speed as a fraction of light speed and θ the angle to our line of sight. With β = 0.75, the ratio is about 49 when the jet points straight at us and about 33 at 20°. This is my own back-of-envelope calculation: it assumes the reported 0.75c is the intrinsic jet speed and that the two jets are intrinsically identical, and I have not seen the paper’s own treatment.

Even so, it shows why the receding jet would be nearly invisible, and why the team infers it from its effect on the surrounding cloud rather than seeing it.

The Particle-Acceleration Claim

The jet pointing away from us is the one that hits the molecular cloud. Where it does, according to the EarthSky account, the interaction produces high-energy gamma rays, and the authors suggest the site may accelerate particles to ultra-high energies, possibly up to a petaelectronvolt (1015 eV). The description of the division of labour is neat: the jet accelerates, the cloud lights up. The accelerator and the target sit tens of parsecs apart.

For scale, the Large Hadron Collider’s proton beams carry 6.8 teraelectronvolts each in the current run (my background knowledge), so a petaelectronvolt particle would be roughly 150 times more energetic than anything in that machine. For a look at what the LHC is being rebuilt to do next, see our teardown of the LHC’s long shutdown.

In gamma-ray astronomy, “ultra-high-energy” generally refers to photons above about 100 TeV (also background knowledge). Sources capable of pushing protons to petaelectronvolt energies are called PeVatrons, and their identification is a long-running goal because cosmic-ray production in the Galaxy is still not fully traced to specific objects. Neutrino astronomy is attacking the same problem from another side, as we covered in our piece on IceCube and the 2026 Physics Nobel.

Where the Claim Is Fragile

  • The identification is a candidate. News coverage calls the object a candidate and says it may be the first confirmed microblazar.
  • The faint jet is inferred. The receding jet is detected through its impact on the cloud, not directly.
  • Acceleration is conditional. The paper’s title says “potential accelerator,” and press accounts use words such as “might” and “likely.” The test of whether the system really produces the nearby gamma rays is still ahead.
  • Numbers vary between reports. Distance and mass come from news coverage rather than the abstract, which carries no numerical values in the text I retrieved.
  • No rapid variability. The explanation, a dense envelope smoothing it out, is a model-dependent reading.

What Comes Next

The team plans deeper observations to watch how the jet evolves, to study how the jet and cloud interact, and to search for more microblazars. If a second and third example turn up, the idea that such systems matter for Galactic cosmic rays would move from a single striking case toward a population statement.

Curved particle accelerator tunnel lined with blue magnets

Frequently Asked Questions

Is the jet a danger to Earth?

No. ZME Science’s report notes that the system poses no newly identified danger to Earth, and at roughly 12,000 light-years the jet’s effects are felt as radio and gamma-ray light.

How is a microblazar different from a blazar?

Scale and engine. A blazar is powered by a supermassive black hole in a galaxy’s core, while a microblazar is a stellar-mass black hole in a binary with a companion star. The viewing geometry, a jet aimed near us, is the shared feature.

Why does PeV energy matter?

Cosmic-ray protons reaching petaelectronvolt energies need very efficient accelerators, and few Galactic sources have been identified that can do it. A microblazar that accelerates particles to such energies would add a new class of candidate.

Sources and Verification Notes

Verification notes: I read the arXiv abstract page, which contains no numerical values, and took distance, period, jet speed, black hole mass and bubble size from two news reports. They disagree in places, and I did not see the paper’s body. The beaming ratios, the LHC beam energy and the comparison with a petaelectronvolt particle are my own calculations and background knowledge. I could not confirm the acceptance by Astronomy & Astrophysics beyond EarthSky’s statement.