A 26-light-year trail of warm gas may solve the mystery of the brightest gamma-ray star system next door

In the Large Magellanic Cloud, a small galaxy about 163,000 light-years away, sits LMC P3 — the brightest known star system of its kind, pouring out gamma rays, the most energetic form of light, for reasons astronomers have argued about since its discovery in 2016. Now a team led by Yasuo Fukui of Nagoya University, working with Gifu University colleagues and using the ALMA radio telescope in Chile, has found a strikingly straight trail of gas about 26 light-years long and 3 light-years wide, warmed to 35 to 60 kelvin — noticeably hotter than the 15-kelvin gas around it. That heated trail looks like the mark left by a powerful jet of particles, strong evidence that LMC P3 hides a microquasar: a small-scale cousin of the brilliant quasars at the centres of distant galaxies, most likely a black hole drawing in material from its companion star, which is more than 30 times heavier than the sun. The findings are published in The Astrophysical Journal Letters.