Free Astronomy Magazine September-October 2022

53 SEPTEMBER-OCTOBER 2022 ASTRO PUBLISHING will soon commence work as an As- sistant Professor of Physics and As- tronomy at the University of Utah. “The resulting explosion is accom- panied by jets moving at close to the speed of light. When one of these jets is pointed at Earth, we observe a short pulse of gamma-ray radiation or a short-duration GRB.” A short-duration GRB usually lasts only a few tenths of a second. Sci- entists then look for an afterglow, an emission of light caused by the interaction of the jets with sur- rounding gas. Even still, they’re dif- ficult to detect; only half-a-dozen short-duration GRBs have been de- tected at radio wavelengths, and until now none had been detected in millimeter wavelengths. Laskar, who led the research while an Excellence Fellow at Radboud University in The Netherlands, said that the difficulty is the immense distance to GRBs, and the techno- logical capabilities of telescopes. “Short-duration GRB afterglows are very luminous and energetic. But these explosions take place in dis- tant galaxies which means the light from them can be quite faint for our telescopes on Earth. Before ALMA, millimeter telescopes were not sensitive enough to detect these afterglows.” Having occurred when the Universe was just 40-percent of its current age, GRB 211106A is no exception. The light from this short-duration gamma-ray burst was so faint that while early X-ray observations with NASA’s Neil Gehrels Swift Observa- tory saw the explosion, the host galaxy was undetectable at that wavelength, and scientists weren’t able to determine exactly where the explosion was coming from. “After- glow light is essential for figuring out which galaxy a burst comes from and for learning more about the burst itself. Initially, when only the X-ray counterpart had been discov- I n a first for radio astronomy, scientists have detected millimeter-wavelength light from a short-duration gamma-ray burst. This artist’s conception shows the merger between a neutron star and another star (seen as a disk, lower left) which caused an explosion resulting in the short-duration gamma-ray burst, GRB 211106A (white jet, middle), and left behind what scientists now know to be one of the most luminous afterglows on record (semi-spherical shock wave mid- right). While dust in the host galaxy obscured most of the visible light (shown as colors), millimeter light from the event (depicted in green) was able to escape and reach the Atacama Large Millimeter/submillimeter Array (ALMA), giving scientists an unprecedented view of this cosmic explosion. From the study, the team confirmed that GRB 211106A is one of the most energetic short-duration GRBs ever observed. [ALMA (ESO/NAOJ/NRAO), M. Weiss (NRAO/AUI/NSF)]