Astronomers have found a bright knot of X-rays close to the centre of the Milky Way that may be the remains of a star that exploded around seventeen centuries ago. The candidate sits inside Sagittarius C, a star-forming region about 26,000 light-years from Earth, and the case for it rests on data from NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton. The findings were published in The Astrophysical Journal by Zhenlin Zhu and Mark Morris of the University of California, Los Angeles, with Gabriele Ponti of Italy’s National Institute for Astrophysics and Ping Zhou of Nanjing University; a record of the paper is available via arXiv.
The word doing the heavy lifting is “possible”.
This is a supernova remnant candidate, not a confirmed one, and that distinction shapes how the whole result should be read.
What the data actually shows
The evidence is a “blob” of X-ray emission, in NASA’s own phrasing, embedded in a larger bubble of expanding gas around a young, massive star. That bubble, where radiation has stripped electrons from hydrogen, is the bright radio source known as Sagittarius C. The X-ray blob is what the team argues could be the wreckage of a massive star that collapsed and exploded.
One detail is easy to miss in the coverage. The X-ray data here is not new. It comes from five Chandra observations taken between July 2001 and August 2014, roughly 57 hours in total, combined with XMM-Newton. What is new is the analysis, not the sighting. That may be the more interesting part of the story: a result pulled from archived data that had been sitting in the record for a decade.
Why ten times brighter matters
The most concrete number in the paper is a brightness comparison. The X-ray emission from the blob is more than ten times brighter than the X-rays from large, known clusters of bright, massive stars. That figure is the team’s main reason for discounting the obvious alternative, which is that the glow comes from a crowd of hot young stars rather than an explosion. On the available evidence, the authors do not think the star-cluster explanation fits.
There is a complication they report plainly, and it cuts against the supernova reading rather than for it. A real remnant should show enhanced amounts of elements forged in the blast, things like iron, oxygen, and silicon. The team searched for that signature and did not find it. Their suggested explanation is that the debris has already mixed into the surrounding gas, which is reasonable for an older remnant.
A non-detection is still a non-detection.
The seventeen-century question
If the blob is a supernova remnant, the team estimates it is expanding at about two million miles per hour, or roughly 3.2 million kilometres per hour, and is at least about 1,700 years old. Counting back from now, “at least 1,700 years” points to an explosion around 300 AD or earlier. The “at least” is worth holding onto, because it is a floor rather than a fixed date, and the event could be considerably older.
This is not the first hint that something detonated here. Observations with NASA’s now-retired SOFIA mission had already shown an expanding shell of gas around Sagittarius C, which suggested a star had exploded in the same spot. The X-ray candidate fits that earlier clue, though fitting a prior hint is not the same as confirmation.
What confirmation would mean
The reason this is worth attention is location. If it holds up, this would be one of the closest supernova remnants ever identified to Sagittarius A*, the supermassive black hole at the galactic centre. That region is dense with massive stars, strong magnetic fields, and fast-moving clouds of gas, all of which make a clean detection harder and a confirmed remnant there especially useful for studying how stars live and die in the most crowded part of the galaxy.
What would settle it is the chemistry. Deeper X-ray observations that either find the missing elemental signature, or rule it out, would do more than another brightness measurement. For now the honest summary is the one the researchers themselves use: a strong candidate, an old prior hint from SOFIA, and a heavy-element search that came back empty. Whether the blob graduates from possible to confirmed is the thing to watch.
