Chandra finds – Supernova remnants in the nearby galaxy Messier 83 did not fade steadily in NASA’s 14-year Chandra X-ray record. Instead, their brightness changed dramatically, pointing to unusual interactions—at least one involving debris colliding with surrounding material,
For years. astronomers have expected the leftovers of a stellar blast to behave like a slow sunset: a supernova goes off. then the X-ray glow from the superheated debris and gas steadily dims. But in a long, painstaking look with NASA’s Chandra X-ray Observatory, several supernova remnants refuse to follow that script.
The observations targeted the galaxy Messier 83 (M83), also known as the Southern Pinwheel, located around 15 million light-years from Earth. Using Chandra data collected from 2000 through 2014. researchers found that the X-ray emissions from supernova remnants there showed surprising variety in how bright they were—and did not simply fade away over time.
The findings were published in the Astrophysical Journal this month.
“We knew that individual X-ray sources could vary dramatically. ” said Andrea Prestwich. an astronomer at the Catholic University of America and the study’s lead author. in a statement. “But finding that so many supernova remnants were behaving this way was a real surprise. Something unusual is going on in these objects. Pinpointing the cause remains a challenge, as M83’s distance limits the detail we can observe.”.
That distance is part of the mystery. With M83 about 15 million light-years away. the team can measure changes in X-ray brightness. but resolving exactly what each remnant is doing—how its structure evolves. where the incoming material is coming from. what compact object might be involved—remains difficult.
One odd remnant, however, comes with a clearer lead. The debris from SN 1957D, a supernova first seen almost 70 years ago, appears to be colliding with material surrounding it. That interaction could help explain the increased X-ray emissions seen from that remnant.
The rest of the story is murkier. For the supernova remnants with changing X-ray outputs, the cause of the variability is unclear.
One possibility raised by the researchers centers on a population of “survivor stars” that may have outlived their companion stars. In that scenario, each X-ray source begins as a binary system: two stars orbiting each other. When the more massive star explodes, the partner does not. The surviving compact activity could then fit what astronomers call a high-mass X-ray binary. or HMXB. which the researchers say could explain the variation in the Chandra readings. HMXBs aren’t new, but they haven’t historically been linked to very many supernova remnants.
Another potential explanation is more of a cosmic recycling picture. After a star dies, it can leave behind a black hole or neutron star. In this idea. that compact object pulls in some of the material originally expelled outward in the explosion—bringing matter back into the system and boosting X-ray emission. Roy Kilgard, a study co-author and a Wesleyan University astronomy professor, put it directly in the same statement.
“This could be an example of cosmic recycling, where debris from the explosion falls back onto the very object the supernova created,” Kilgard said. “And it’s quite possible that both explanations are at play—different sources in our sample may have different origins.”
Taken together, the Chandra record points to a more complicated aftermath for massive stars than astronomers have traditionally modeled. The sequence is harder to predict when an expanding remnant can be repeatedly energized—either by collisions with nearby material. by interaction with a surviving companion system. or by debris returning to a compact remnant.
The puzzle isn’t limited to M83. A follow-up study also revealed variable supernova remnants in Messier 51 (M51), the Whirlpool Galaxy.
A composite image of M51 combines data from NASA’s Chandra X-ray Observatory (purple) with optical data (red, green and blue) taken with ground-based telescopes by a team of astrophotographers.
NASA/CXC/SAO (Chandra x-ray data); C.Björk/T.Bähnck/S. Donoso/J. Gentillon/A. and D. Grelin/S. Guberski/R. Hall/T. Heuberger/J. Jacks/P. Kent/Br. Meyers/W. Ostling/N. Puig/T. Schaeffer/F. Schöfbänker/M. Vasilev (Astrobin/optical ground-based data)
For now. the human reality of the science is this: the remnants are telling us they’re still changing. even long after the explosion. The bright and fading X-ray signals add urgency to the next step—figuring out what mechanism is at work in each object. and why their timelines refuse to match the neat fading models astronomers have relied on.
NASA Chandra X-ray Observatory supernova remnants Messier 83 M83 Messier 51 M51 Astrophysical Journal X-ray variability high-mass X-ray binary HMXB SN 1957D cosmic recycling black hole neutron star stellar evolution