A hidden cosmic engine operating inside the expanding debris
A luz que no debería existir llegó desde las profundidades del cosmos en 2017, y durante años desafió toda explicación: una supernova diez veces más brillante de lo normal, acompañada de rayos gamma que nadie podía confirmar ni comprender. Investigadores españoles del ICE-CSIC en Barcelona han resuelto ahora ese enigma, identificando como probable culpable a un magnetar recién nacido —una estrella de neutrones con campos magnéticos de una intensidad casi inconcebible— que actuó como motor oculto de la explosión. El hallazgo, publicado en Astronomy & Astrophysics, no solo cierra un misterio de casi una década, sino que abre una nueva vía para entender cómo mueren las estrellas más masivas del universo.
- Durante casi nueve años, la señal de rayos gamma detectada por el telescopio Fermi de la NASA en la supernova SN 2017egm permaneció sin explicación, un dato incómodo que los modelos existentes no podían absorber.
- La anomalía era doble: la explosión brillaba diez veces más que una supernova ordinaria y emitía un tipo de radiación que no se esperaba de ese tipo de evento, lo que ponía en cuestión los modelos estándar de colapso estelar.
- El equipo del ICE-CSIC adoptó un enfoque sistemático, analizando dieciséis años de observaciones de Fermi sobre las seis supernovas hiperluminosas más cercanas, buscando en cada una la huella inequívoca de los rayos gamma.
- Solo SN 2017egm superó la prueba, confirmando que al menos algunas supernovas pueden brillar en rayos gamma con la misma intensidad que en luz visible —una posibilidad teórica que por fin tiene respaldo observacional.
- El modelo que mejor encaja con los datos apunta a un magnetar recién formado: un objeto con campos magnéticos mil veces más intensos que los de una estrella de neutrones típica, capaz de actuar como motor interno y alimentar tanto la luz visible como la emisión de rayos gamma.
En 2017, el telescopio espacial Fermi de la NASA captó algo perturbador: una ráfaga de rayos gamma procedente de una supernova que, según los modelos conocidos, no debería haberlos producido. La explosión, bautizada como SN 2017egm y situada a 440 millones de años luz en la galaxia NGC 3191, ya era excepcional por su luminosidad —diez veces superior a la de un colapso estelar ordinario—. Pero la señal de rayos gamma resistió toda interpretación durante años.
El misterio ha encontrado respuesta gracias al trabajo de investigadores del Instituto de Ciencias del Espacio (ICE-CSIC) de Barcelona. El equipo, liderado por Guillem Martí-Devesa, revisó metódicamente los datos del telescopio Fermi correspondientes a las seis supernovas hiperluminosas más cercanas registradas en sus primeros dieciséis años de operación. El resultado fue contundente: de todas ellas, solo SN 2017egm mostraba evidencia clara de emisión gamma, lo que convirtió este caso en un hallazgo singular dentro de su categoría.
La explicación más coherente con los datos apunta a la formación de un magnetar en el instante del colapso estelar. Estas estrellas de neutrones poseen campos magnéticos hasta mil veces más intensos que los de sus equivalentes ordinarios, y pueden funcionar como motores internos que canalizan energía hacia el exterior de la explosión. El momento en que los rayos gamma comenzaron a escapar de los restos de la supernova —aproximadamente tres meses después del colapso— coincide con lo que predicen los modelos de explosiones impulsadas por magnetares.
El hallazgo, publicado en Astronomy & Astrophysics, tiene implicaciones que van más allá de un caso concreto. Sugiere que algunas supernovas hiperluminosas no se explican únicamente por la energía liberada en el colapso, sino por la actividad de un objeto compacto y extremo que opera en su interior. SN 2017egm se convierte así en un modelo de referencia para identificar eventos similares en el universo distante y para afinar nuestra comprensión de las muertes estelares más violentas que conocemos.
In 2017, NASA's Fermi Gamma-ray Space Telescope detected something unusual: a burst of gamma rays arriving from a distant supernova that shouldn't have been producing them. The explosion, called SN 2017egm, was already extraordinary—a hyperluminous supernova situated 440 million light-years away in the galaxy NGC 3191, blazing with ten times the visible light of an ordinary stellar collapse. But the gamma-ray signal remained a puzzle. For years, astronomers couldn't definitively confirm what they were seeing or explain where the energy was coming from.
That mystery has now been solved, thanks in part to Spanish researchers at the Institute of Space Sciences (ICE-CSIC) in Barcelona. Their work, published in Astronomy & Astrophysics, reanalyzed data from Fermi's Large Area Telescope and confirmed that the gamma rays were real—a finding that opens a new window into understanding some of the universe's most violent events.
The Spanish team's approach was methodical. Researcher Guillem Martí-Devesa and his colleagues examined Fermi observations of the six nearest hyperluminous supernovae detected during the telescope's first sixteen years of operation. They were searching for gamma-ray signatures in each one. The result was striking: only SN 2017egm showed clear evidence of gamma rays. This wasn't just confirmation of a faint signal—it demonstrated that at least some supernovae can shine as brightly in gamma rays as they do in visible light, a possibility that had been suspected but never firmly established.
The explanation that best fits the data points to something exotic: a magnetar. These are neutron stars born from stellar collapse, but with magnetic fields so extraordinarily intense they dwarf anything else in the cosmos. A typical neutron star already possesses a magnetic field millions of times stronger than Earth's. A magnetar takes that to another extreme, reaching fields up to a thousand times more powerful than a standard neutron star. In the moments after a massive star collapses, if the conditions are right, such an object can form—and it can act like an internal engine, channeling tremendous energy outward.
When the team compared their optical and gamma-ray observations against theoretical models, the newborn magnetar hypothesis fit best. The brightness of the initial explosion and the timing of when gamma rays began escaping from the supernova's debris—roughly three months after the stellar collapse—aligned with what a magnetar-powered explosion would produce. The magnetar's intense magnetic field would have been capable of accelerating particles and generating the gamma-ray burst that Fermi detected, while simultaneously driving the exceptional visible-light output that made SN 2017egm so luminous.
This finding matters because it suggests a new mechanism for understanding hyperluminous supernovae. Rather than relying solely on the energy released by the collapse itself, some of these explosions may be powered by the rapid spin and magnetic field of a newly formed magnetar—a hidden cosmic engine operating inside the expanding debris. The confirmation that SN 2017egm produced detectable gamma rays, and that this radiation is consistent with magnetar-powered models, provides astronomers with a concrete example to study. As research continues, this case will likely serve as a template for identifying similar events in the distant universe and refining our understanding of how the most extreme stellar deaths unfold.
Citações Notáveis
Only SN 2017egm shows evidence of gamma rays, confirming that some supernovae can be as luminous in gamma rays as in visible light— Guillem Martí-Devesa, ICE-CSIC researcher
A Conversa do Hearth Outra perspectiva sobre a história
Why did it take so long to figure out what was powering this supernova?
The signal was there all along in Fermi's data, but gamma rays from supernovae are rare enough that confirming the detection required careful analysis. You have to rule out noise, instrumental artifacts, and other sources. It's not like seeing something obvious.
So the Spanish team just looked harder at old data?
They looked smarter. They took six of the nearest hyperluminous supernovae and applied the same rigorous search method to all of them. By finding that only one showed gamma rays, they could say with confidence that the signal in SN 2017egm was real, not a fluke.
What makes a magnetar different from a regular neutron star?
Imagine compressing the entire mass of the sun into a sphere the size of a city. That's a neutron star. Now imagine the magnetic field is a thousand times stronger than what you'd find in that already-extreme object. That's a magnetar. The field is so intense it can reshape atoms and accelerate particles to relativistic speeds.
And this magnetar was born from the same collapse that created the supernova?
Exactly. When the massive star collapsed, it didn't just explode outward—it left behind a magnetar. That newborn object, spinning rapidly with its extreme magnetic field, became the engine that powered the explosion's exceptional brightness.
Why does this matter for future observations?
Because now astronomers have a concrete case study. They can use SN 2017egm as a template for identifying other magnetar-powered supernovae. It gives them a way to connect visible light, gamma rays, and the physics of neutron stars in a single event.
Will we see more of these?
Almost certainly. If magnetars can power hyperluminous supernovae, then the universe probably contains more examples we haven't recognized yet. This discovery is really about learning how to look.