Header image: Artist's illustration of GRB 250702B-the longest gamma-ray burst ever observed-shows a high-speed jet of material being launched from a source. Credit: NOIRLab/NSF/AURA/M. Garlick
On January 26, 2026, the Submillimeter Array (SMA) on Maunakea crossed an important threshold for real-time astronomy.
For the first time, scientists from the Center for Astrophysics | Harvard & Smithsonian (CfA) and collaborators demonstrated a new rapid‑response capability at millimeter and submillimeter wavelengths-the invisible light that reveals otherwise hidden details of cosmic explosions. SMA zoomed in on a gamma‑ray burst (GRB) within minutes of its discovery and captured the earliest observations of such an event ever made at these frequencies.
"Getting data minutes after an explosion-it's just not a thing that was possible," said Tanmoy Laskar, assistant professor of physics and astronomy at the University of Utah and a coauthor of the study. "Now, we can learn about properties of these gamma ray bursts in a time frame that was impossible before."
GRBs are the brightest explosions in the universe-brief but staggeringly immense flashes produced by jets launched in the collapse of massive stars or the merger of compact objects like neutron stars. Their initial burst is followed by a glow that X-ray and optical telescopes have long been able to chase within seconds or minutes of the event, but that millimeter-wave telescopes have historically lagged behind in observing.
That changed in January of this year, when the SMA rapidly responded to an automated alert from NASA's Neil Gehrels Swift Observatory, which detected a flash of gamma rays. The sequence played out almost entirely without human intervention. Within 90 seconds, the on-duty operator had been alerted. Within four minutes, the telescope was moving to start observations.
"It was an incredible thing to watch in real time," said Garrett Keating, an astrophysicist at CfA and deputy director of the SMA, who led the rapid-response effort. "Being able to react and process data this quickly is a big departure from how SMA usually operates, but it was absolutely critical for capturing an event where minutes matter. This was the first time we had the full system online. We learned a lot from the experience and think we can get the response time down to as little as two to three minutes."
Within thirteen minutes, the telescopes were on target, and a separate automated analysis was already generating images of the explosion in near real-time.
"With interferometry, we don't get direct images from the telescope," explained Ranjani Srinavasan, interim director of the SMA. "Usually that process takes a long time."
The response time is roughly 100 times faster than the typical response time for millimeter and submillimeter telescopes.
"The SMA's new capability is a gamechanger for the field," said Edo Berger, professor of astronomy at Harvard and a co-author of the study.
Follow‑up observations two days later showed that the source had faded, strengthening the case that SMA had indeed captured a transient afterglow rather than a steady background galaxy.
"This new capability opens a unique window into the physics behind some of the most powerful stellar explosions," the U's Laskar added. "With the SMA, we can now probe the structure and composition of the ejecta in unprecedented detail, bringing us closer to understanding how these explosions launch their powerful jets."
The fast observations mark the launch of the SMA Sub/millimeter Program to Rapidly Investigate Novel Time‑domain Sources (SMA SPRINTS), a program designed to use the SMA and its wideband upgrade, called wSMA, to provide quick, sensitive and flexible follow‑up of transient events across the time‑variable sky.
The goal is to be ready as new facilities such as the Rubin Observatory's Legacy Survey of Space and Time (LSST) and, later, the Roman Space Telescope, begin sending large numbers of alerts to the astronomy community.
