Astronomers get rare glimpse at supernova explosion with help from Kitt Peak telescope

The interstellar excitement began on March 21, when a space telescope called the Einstein Probe detected a brief flash of X-rays from a galaxy about 500 million light-years away.

Within an hour, several ground-based telescopes began monitoring the source, which soon revealed itself as the final explosion of a massive dying star.

The rare observation was announced Wednesday by the Tucson-based National Optical Infrared Astronomy Research Lab, or NOIRLab, which oversees Kitt Peak and observatories in Hawaii and Chile for the U.S. National Science Foundation.

The first outward sign of a supernova is a shock wave of ultraviolet and X-ray radiation bursting through the surface of the exploding star. Such shock breakouts are difficult to observe because they last only hours or seconds.

It took two international teams of astronomers using telescopes across the globe to identify the shock wave and study the aftermath of the supernova that has since been designated as SN 2026gzf. They detail their discovery in a pair of new scientific papers published in The Astrophysical Journal Letters.

“Our observations allowed us to study the physics of three pieces of this explosion: the X-ray shock breakout, the accompanying supernova, and the interaction of the supernova with material previously cast out by the dying star,” said Jillian Rastinejad, a NASA Einstein Fellow at the University of Maryland who led one of the teams. “With this information we were able to map out the structure of the material surrounding the star and understand the star’s violent lifestyle before it collapsed.”

Some of those observations were made using the Dark Energy Spectroscopic Instrument — DESI for short — mounted to Kitt Peak’s Mayall 4-meter Telescope.

DESI can capture the light from scores of galaxies at once using an array of 5,000 fibers pointed at the night sky and connected to 10 spectrographs packed into a room below the Mayall Telescope’s main floor.

When some of the instrument’s fibers are not already matched to objects in space, they can be used to track transient astronomical events picked up by NOIRLab’s new Vera C. Rubin Observatory in Chile, an $800 million telescope that is in the second year of a constant, decade-long scan of the night sky as part of the Legacy Survey of Space and Time.

“DESI’s spare-fiber program gave us the opportunity to return to SN 2026gzf repeatedly and follow how its spectrum changed as the explosion evolved,” said Xander Hall, a graduate student at Carnegie Mellon University and one of the co-authors of the new paper. “This sequence of observations demonstrates the power of using DESI’s spare fibers for rapid transient follow-up and classification as Rubin continues to ramp up its transient alert stream over the next decade.”

Researchers believe the type of dying star at the center of the supernova had already undergone a series of mass ejections before its final collapse, shedding its hydrogen and helium into shells surrounding it.

“This is the first time we’ve mapped out the pre-explosion environment of a star that has been stripped of hydrogen and helium,” said co-author Gokul Srinivasaragavan, a recent PhD graduate from the University of Maryland and a member of Rastinejad’s team. “Going forward, I’m excited to observe more shock breakout events in similar detail to test if all stripped stars have a similar ‘lifestyle’ prior to collapse and what, if any, differences we see.”

Astronomers were puzzled by the way the supernova unfolded. The initial shock wave was the weakest ever detected from an event of this type, and it apparently did not produce an expected gamma-ray burst, the brightest and most powerful class of explosions in the known universe.

Researchers also found no sign of what’s known as a “relativistic jet” of material moving at close to the speed of light, something commonly associated with supernovae like this.

“One possibility is that the jet was ‘choked,’ either by the surface of the star or by circumstellar material surrounding the star,” said Brendan O’Connor, the McWilliams Fellow at Carnegie Mellon University who led the other team of astronomers.

The findings suggest that massive stars can die in a wider range of ways than previously known.

The only other time the initial shock breakout from a supernova has been directly and definitively detected by astronomers came in 2008, with an observation that also had an Old Pueblo connection.

The explosion, designated as SN 2008D, was detected at a distance of about 88 million light-years by NASA’s Neil Gehrels Swift Observatory, a gamma-ray-detecting space probe whose namesake astronomer grew up in Tucson and graduated from the University of Arizona.

Advanced instruments such as the Einstein Probe and the Rubin Telescope are expected to lead to more real-time observations of supernovae as they unfold.

Only a few such explosions are thought to occur in our own Milky Way each century, but in a universe of billions of galaxies, there is likely to be a dying star exploding somewhere at any given second.