Weighing a Stellar Giant Baby express
At the center of a cosmic dust cloud, astronomers detected an invisible star. It's wrapped in a rotating gas disk. This disk works like a set of scales: the gas speed at different distances from the center reveals the star’s mass.
Observing in the radio range, scientists peered through cosmic dust and measured gas velocities using spectroscopy — breaking light into colors. They found carbon monoxide (carbon) and sulfur in the disk. The outer regions spin slowly, just a kilometer or two per second, while closer to the star, the gas races tens of times faster. This gradient, like the needle of a scale, pointed to the exact mass.
Original abstract
as written by the authors arXiv:2601.12336
We investigate the circumstellar environment of the O-type bloated star candidate IRAS 19520+2759 (I19520) using high-resolution observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Expanded Very Large Array (EVLA). Radio continuum emission traced by the EVLA (C, K, and Q bands) exhibits a spectral index of 0.5, consistent with a thermal jet. ALMA 1.3 mm continuum map reveals a compact source coincident with the optical counterpart of I19520, likely tracing the dense core hosting the central massive young stellar object. A prominent molecular outflow in the east-west direction, along with a possible secondary outflow oriented northeast-southwest, is identified in the $$^{13}\mathrm{CO}$$ emission. A hot molecular core and a Keplerian disk are detected in several $$\mathrm{SO}_2$$ transitions. Assuming an edge-on disk geometry, the dynamical mass of the central object is estimated to be in the range of $$10$$-$$15~M_\odot$$.
The star is only a few tens of thousands of years old, a blink in cosmic time, yet it already weighs as much as 15 Suns. For comparison, our Sun is 4.5 billion years old and is only halfway through its life.