A chance to watch a pulsar from its infancy
For thirty-four years, the aftermath of SN 1987A — the nearest supernova witnessed by human eyes in four centuries — harbored a secret at its core. In February 2021, astronomers using three of the world's most powerful observatories found what theory had long promised but observation could never confirm: the fingerprint of a pulsar, a newborn neutron star spinning in the wreckage of a stellar death. The discovery reminds us that the universe does not always reveal its deepest truths at once, but conceals them behind veils of its own making — veils that, in time, it allows to lift.
- For over three decades, a glaring gap in astrophysical knowledge persisted: a pulsar that theory demanded should exist at the heart of SN 1987A simply could not be found.
- A team led by Emanuele Greco at the University of Palermo combined data from Chandra, NuSTAR, and ALMA to detect a pulsar wind nebula — the energetic halo a spinning neutron star blows around itself — proving something is there even if the source remains hidden.
- The culprit behind the long silence is the supernova's own debris: a thick shroud of gas and dust that swallows the X-rays the pulsar emits, like a flashlight lost inside a fog bank.
- That fog is thinning — models predict the obscuring material will dissipate enough within the next decade to expose the pulsar to direct observation for the first time.
On a February night in 1987, astronomers watched a star explode in the Large Magellanic Cloud — the closest supernova to Earth in four hundred years. They named it SN 1987A, studied it relentlessly, and waited for what physics said must follow: a pulsar, a rapidly spinning neutron star born from the stellar collapse. Decades passed. Hints emerged and dissolved. The missing pulsar became one of astronomy's most stubborn open questions.
In February 2021, a team led by Emanuele Greco at the University of Palermo announced a breakthrough. Drawing on coordinated observations from NASA's Chandra X-ray Observatory, NASA's NuSTAR, and the ground-based Atacama Large Millimeter Array in Chile, the researchers detected a pulsar wind nebula at SN 1987A's core — the characteristic shell of energetic particles that a spinning neutron star blows outward. They had not seen the pulsar itself, but they had found its unmistakable signature.
The reason for the long silence turned out to be the supernova's own aftermath. A thick envelope of gas and dust — ejected by the original explosion — had been absorbing the pulsar's X-ray emissions all along, rendering it invisible. But this veil is not permanent. The material is expanding and thinning, and the team's models suggest it will clear sufficiently within the next decade to allow direct observation.
When that moment arrives, astronomers will gain something without precedent: a front-row view of the youngest pulsar ever directly observed, offering a rare chance to watch a neutron star develop from its earliest moments. The question is no longer whether the pulsar exists — it is simply a matter of waiting for the fog to lift.
On a February night in 1987, astronomers turned their instruments toward an explosion in the Large Magellanic Cloud—a satellite galaxy orbiting the Milky Way—and witnessed the closest supernova to Earth in four centuries. They named it SN 1987A, and it became one of the most scrutinized objects in the sky. But there was a problem that would nag at the field for more than three decades: what was left behind?
Theory suggested the answer. When a massive star collapses and explodes as a supernova, it often leaves behind a neutron star—a pulsar, in the case of a rapidly spinning one. The physics pointed to this outcome for SN 1987A. Yet despite years of searching through the stellar wreckage, no one could find it. There were hints, tantalizing clues that seemed to lead somewhere, only to evaporate under closer inspection. The missing pulsar became a puzzle that refused to resolve.
Then, in February 2021, a team led by Emanuele Greco at the University of Palermo announced they had found it—or at least, strong evidence that it was there. Using data from three observatories working in concert—NASA's Chandra X-ray Observatory, NASA's NuSTAR, and the ground-based Atacama Large Millimeter Array in Chile—the researchers detected a pulsar wind nebula at the heart of SN 1987A. This is the signature of a pulsar: a shell of energetic particles and radiation blown outward by the spinning neutron star at its center. They hadn't seen the pulsar directly. But they had seen its fingerprint.
The reason for the decades of silence became clear. The newborn pulsar sits shrouded in a thick envelope of gas and dust—the very material ejected by the supernova explosion itself. This veil absorbs the X-rays the pulsar would normally emit, rendering it invisible to direct observation. It is as if someone is shining a flashlight through fog. The light is there, but you cannot see the source.
What makes this finding more than just another detection is what the models predict next. The dust and gas surrounding the pulsar are not permanent fixtures. They are dissipating, thinning out as they expand into space. Within the next decade, according to the team's calculations, this obscuring material should clear enough to reveal the pulsar itself. When that happens, astronomers will have something unprecedented: a chance to watch a pulsar from its infancy, to observe how a newborn neutron star develops and evolves in real time. At 168,000 light-years away, it will not be the closest pulsar known to Earth. But it will be the youngest ever directly observed—a cosmic laboratory for understanding how these extreme objects are born and mature.
For now, the mystery that has occupied astronomers for 34 years has shifted from whether the pulsar exists to when it will finally become visible. The answer, it seems, is soon.
Citas Notables
For 34 years, astronomers have been sifting through the stellar debris of SN 1987A to find the neutron star we expect to be there.— Emanuele Greco, University of Palermo
Being able to watch a pulsar essentially since its birth would be unprecedented. It might be a once-in-a-lifetime opportunity to study the development of a baby pulsar.— Salvatore Orlando, Palermo Astronomical Observatory
La Conversación del Hearth Otra perspectiva de la historia
Why did it take so long to find this pulsar if the theory predicted it should be there?
Because theory and observation are different things. The supernova itself created a shroud of material that blocks the very light we'd need to see the pulsar. It's like looking for a newborn in a delivery room full of smoke.
So they didn't actually see the pulsar. They saw something else and inferred the pulsar was there?
Exactly. They detected a pulsar wind nebula—the shell of energy and particles that a spinning neutron star creates around itself. That signature is unmistakable. It's like finding footprints in the snow and knowing someone walked there, even if you didn't see them.
And the dust is going away?
Yes. The material that exploded outward is still expanding, getting thinner as it spreads. Within ten years, it should be transparent enough that we can see the pulsar directly.
What makes that moment important?
We've never watched a pulsar from birth before. Every pulsar we've studied has already aged millions of years. This one is only 34 years old. Watching it develop from here on would be like having a time-lapse film of how these objects actually work.
Is there any chance they're wrong about what's there?
There are alternative explanations for what they observed, but they're much less likely given what we know about how pulsars behave. The combined data from three different observatories all point the same direction.