Team led by Fukui and Rajendra detects cool molecular jet in Large Magellanic Cloud

Yasuo Fukui of Nagoya University and Bhuvana Gadikere Rajendra of Gifu University led a team that used the ALMA observatory in Chile to detect a cool molecular jet from microquasar LMC P3 in the Large Magellanic Cloud, inside supernova remnant DEM L241, reporting in 2026. In a microquasar, a stellar-mass black hole or neutron star pairs with a companion star, and matter from its accretion disk produces X-ray and gamma-ray emissions plus jets near light speed.

According to the team’s 2026 report, the jet is a narrow trail of heated molecular gas measuring roughly 26 light-years long by about three light-years wide. The jet’s carbon monoxide gas is 35 to 60 kelvin, far above the roughly 15 kelvin of gas around it, though still cold. “We discovered a gigantic molecular jet,” said Fukui. Fukui compared the jet’s length to the roughly 25-light-year distance to Vega, saying the trail would stretch from Earth to that star.

LMC P3 ranks as the most luminous gamma-ray binary known, pairing a compact object — possibly a black hole or neutron star — with a massive O-type star with a mass more than 30 times that of the Sun. The two stars complete an orbit in roughly 10 days, and Fermi recorded a 10.3-day period in the system’s gamma-ray emissions. LMC P3 lies inside supernova remnant DEM L241, a molecular gas cloud left by the supernova that formed its compact object, although the remnant accounts for only part of the gamma-ray emissions.

In 2016, astronomers found LMC P3 through unusually strong gamma-ray emissions, the first gamma-ray binary identified outside the Milky Way. From the outset, astronomers suspected LMC P3 was an X-ray binary, and Chandra X-ray Observatory studies appeared to confirm it. Gamma rays occupy the upper edge of the electromagnetic spectrum.

Earlier, scientists divided between two explanations for the gamma rays: pulsar winds from a spinning neutron star striking the companion’s stellar wind, or a microquasar accretion disk. Under that idea, a rapidly spinning neutron star drives energetic particles into the stellar wind of its companion, creating a shock wave that accelerates particles and produces gamma rays. A neutron star is the leftover of a collapsed supermassive star, consisting only of neutrons packed tightly into a space about as big as a city.

ALMA began observing DEM L241/LMC P3 in 2022 with bands 6 and 7, capturing carbon monoxide emission at wavelengths of 1.3 mm and 0.87 mm to learn about the gas’s structure, movement and temperature. The work grew out of years spent mapping one supernova remnant in detail. Carbon monoxide traces cold molecular gas, and its emission reveals the gas’s temperature.

The study appeared in The Astrophysical Journal Letters in 2026 under DOI 10.3847/2041-8213/aea0cb. The paper was co-led by Bhuvana Gadikere Rajendra and Kisetsu Tsuge of Gifu University’s Institute for Advanced Study, with Hidetoshi Sano also at Gifu University. Fukui, professor emeritus at Nagoya University, led the LMC P3 discovery paper.

The team interprets the warmth as shock heating from a microquasar jet connected to the gamma-ray binary, whose accretion disk receives winds from the O-star, in line with simulations of a jet hitting an interstellar cloud. The one-sided CO jet aligns strikingly with the binary, indicating LMC P3 drove it. The authors call the straight, thin, warm trail evidence of cool molecular jets produced by a microquasar, since a spherical supernova shock cannot readily produce such a shape while a compact object’s focused jet heating gas it encounters fits the trail better. Fukui said the elevated temperature across much of the molecular cloud points to the gas meeting a jet from the compact object, one that could also power LMC P3’s gamma rays.

Microquasars are small-scale versions of quasars, among the universe’s most luminous objects, found in distant galaxies and powered by supermassive black holes at galactic cores. Only a few microquasars exist beyond the Milky Way, and LMC P3 is one of them.

This is only the second known case of cool molecular jets potentially driven by a microquasar; the first is HESS J1023-575, a Milky Way microquasar candidate. According to the arXiv abstract, the one-sided CO jet measures 8 pc long by 1 pc wide, with a weaker second jet candidate tilted at a slightly different angle. The abstract estimates the jet at 33-60 K versus about 15 K in nearby gas outside the jet and finds no radiative heat source. The high temperatures, it says, result from shock heating rather than a radiative source.

The team says sub-millimeter observations could open a new way to identify and study microquasars. The Large Magellanic Cloud is a dwarf satellite galaxy of the Milky Way roughly 163,000 light-years from Earth, offering a clear view unlike toward the dust-shrouded galactic core. From nearby, the cloud offers an unobstructed extragalactic laboratory for studying microquasar jets and their surroundings.

Alongside SS 433, the first microquasar ever found, the LMC P3 result adds insight into compact objects and how they interact with surrounding material. Whether the compact object is a black hole or neutron star remains unknown, and the team has announced no further observations. Fukui said black-hole jets are more powerful than neutron-star jets, so LMC P3’s strong gamma-ray output points to a black hole at its center rather than a neutron star. The discovery carries broad implications for studying high-energy emissions and the objects behind them.