Free Astronomy Magazine March-April 2026

L eft: The stellar field around the host galaxy of GRB 250702B — the longest gamma-ray burst that astronomers have ever observed. It comprises observations from the Gemini North telescope, one half of the International Gemini Observatory, funded in part by the U.S. National Science Founda- tion and operated by NSF NOIRLab, as well as the U.S. Department of Energy-fabricated Dark Energy Camera, mounted on the NSF Víctor M. Blanco 4- meter Telescope at Cerro Tololo Inter-American Ob- servatory, a Program of NSF NOIRLab. Right: Close-up view of the host galaxy taken with the Gemini North telescope. This image is the result of over two hours of observation, yet the host galaxy appears extremely faint due to the large amount of dust surrounding it. [International Gemini Observa- tory/CTIO/ NOIRLab/DOE/NSF/AURA. Image process- ing: J. Miller (International Gemini Observatory/NSF NOIRLab), M. Zamani & D. de Martin (NSF NOIRLab)] nearly two hours of observations to capture the faint signal from beneath the swaths of dust. Car- ney and his team then combined these data with new observations taken with the Keck I Telescope at W. M. Keck Observatory, the Magellan Baade Telescope, and the Fraunhofer Telescope at Wen- delstein Observatory, as well as publicly available data from VLT, NASA’s Hubble Space Telescope (HST), and X-ray and radio observatories. They then compared this robust dataset with theoreti- cal models, which are frameworks that explain the behavior of astronom- ical phenom- ena. Models can be used to make pre- dictions that can then be tested against observational data to refine scientists’ understanding. The team’s analysis established that the initial gamma-ray signal likely came from a narrow, high-speed jet of ma- terial crashing into the surrounding ma- terial, known as a relativistic jet. The analysis also helped characterize the en- vironment around the GRB and the host galaxy overall. They found that there is a large amount of dust surrounding the location of the burst, and that the host galaxy is extremely massive compared to most GRB hosts. The data support a picture in which the GRB source resides in a dense, dusty environment, possibly a thick lane of dust present in the host 42 MARCH-APRIL 2026 ASTRO PUBLISHING sists of the Gemini North telescope in Hawai’i and the Gemini South tel- escope in Chile. It is partly funded by NSF and operated by NSF NOIRLab. “The ability to rapidly point the Blanco and Gemini telescopes on short notice is crucial to capturing transient events such as gamma-ray bursts,” says Carney. “Without this ability, we would be limited in our understanding of distant events in the dynamic night sky.” The team used a suite of instruments for their investigation: the NEW- FIRM wide-field infrared imager and the 570-megapixel DOE-fabricated Dark Energy Camera (DECam), both mounted on the Blanco telescope, and the Gemini Multi-Object Spec- trographs (GMOS) mounted on Gemini North and Gemini South. Analysis of the observations re- vealed that GRB 250702B could not be seen in visible light, partly due to interstellar dust in our own Milky Way Galaxy, but more so due to dust in the GRB’s host galaxy. In fact, Gemini North, which provided the only close-to-visible-wavelength de- tection of the host galaxy, required https://noirlab.edu/public/videos/noirlab2531a/?nocache=true& T his visualization illustrates the process of pinpointing the location of the 2 July outburst and its host galaxy. Multiple facilities in space and on Earth, collecting light across the spectrum, guided astronomers to the source. [NASA’s Goddard Space Flight Center and A. Mellinger, CMU]