Even a low-probability detection was worth pursuing
Desde 1983, un satélite infrarrojo barrió los cielos en busca de lo invisible, sin saber que quizás rozó algo enorme. Casi cuatro décadas después, el astrónomo Michael Rowan-Robinson revisó ese archivo olvidado y encontró tres señales tenues que podrían corresponder al esquivo Planeta Nueve, un mundo hipotético de tres a cinco masas terrestres orbitando a 225 unidades astronómicas del Sol. La detección es incierta, los datos son ruidosos, y la probabilidad no es abrumadora —pero en la búsqueda de mundos desconocidos, incluso una pista frágil puede reorientar el telescopio de la humanidad hacia el lugar correcto.
- Durante cinco años, los astrónomos buscaron el Planeta Nueve en tiempo real sin encontrar nada, hasta que alguien decidió buscar en el pasado.
- Tres señales débiles en datos de 1983 parecen trazar el movimiento de un único objeto frío y distante, justo en el límite de lo que el satélite IRAS podía detectar.
- El problema: la zona del cielo está contaminada por cirros galácticos, nubes de polvo infrarrojo que pueden imitar objetos reales y sembrar dudas sobre cualquier señal.
- Pan-STARRS, un telescopio moderno y más sensible, apuntó a la misma región y no encontró nada, lo que deja la detección en un limbo entre el hallazgo y el espejismo.
- Rowan-Robinson no afirma haber encontrado el planeta, sino haber encontrado una coordenada: un punto de partida para búsquedas futuras más precisas y dirigidas.
En 2016, los astrónomos propusieron la existencia de un planeta masivo más allá de Neptuno, cuya influencia gravitacional explicaría las órbitas anómalas de ciertos cuerpos helados en los confines del sistema solar. Lo llamaron Planeta Nueve. Durante cinco años, los telescopios lo buscaron sin éxito.
En otoño de 2021, Michael Rowan-Robinson, del Imperial College de Londres, tomó un camino distinto: en lugar de mirar al cielo, revisó datos del satélite infrarrojo IRAS, que en 1983 pasó diez meses escaneando el universo en busca de objetos demasiado fríos y distantes para la luz visible. De un catálogo de unos 250.000 puntos registrados, Rowan-Robinson aisló tres señales —de junio, julio y septiembre de 1983— que parecían trazar el movimiento de un único objeto a través del cielo.
Las señales eran débiles y estaban al límite de la capacidad del satélite. La región estaba llena de cirros galácticos, nubes de polvo que brillan en infrarrojo y pueden confundirse con objetos reales. El propio Rowan-Robinson admitió que la probabilidad de que fueran genuinas no era abrumadora, aunque consideró que valía la pena publicarlas y someterlas a revisión científica.
Si las señales fueran reales, apuntarían a un mundo de tres a cinco masas terrestres orbitando a unos 225 unidades astronómicas del Sol, más de veinte veces más lejos que Neptuno. Sin embargo, Pan-STARRS, un telescopio más moderno y sensible, ya había escaneado esa misma zona sin encontrar nada coincidente. Rowan-Robinson no afirmó haber descubierto el Planeta Nueve: afirmó haber encontrado un hilo del pasado que, si se tira con cuidado, podría llevar a algún lugar real. La búsqueda continúa.
In 2016, astronomers proposed the existence of a massive world orbiting far beyond Neptune, a planet they had never seen but whose gravitational influence seemed to explain the peculiar paths of distant icy bodies. They called it Planet Nine. For five years, telescopes pointed skyward in search of it, finding nothing. Then, in the fall of 2021, a researcher at Imperial College London decided to look backward—not at the sky, but at data collected nearly four decades earlier.
Michael Rowan-Robinson pulled up observations from IRAS, the Infrared Astronomical Satellite, which had spent ten months scanning the heavens starting in January 1983. The satellite had been designed to detect objects too cold and distant to show up in visible light, making it theoretically capable of spotting something like Planet Nine. From a catalog of roughly 250,000 point sources IRAS had recorded, Rowan-Robinson isolated three signals that stood out: detections made in June, July, and September of 1983 that appeared to trace the movement of a single object across the sky.
The signals were faint and sat at the very edge of what IRAS could reliably detect. The region of sky where they appeared was crowded with galactic cirrus—wispy clouds of dust that glow in infrared wavelengths and create noise that can mimic real objects. Rowan-Robinson himself acknowledged the odds were not in favor of these being genuine. The probability, he wrote, was not overwhelming. Yet the possibility intrigued him enough to publish his findings in a preprint server and submit them for peer review in Monthly Notices of the Royal Astronomical Society.
If the signals were real, they would tell us something concrete about Planet Nine. The data suggested a world between three and five times Earth's mass, orbiting at roughly 225 astronomical units from the Sun—more than twenty times farther out than Neptune. That distance places it in a region of space so remote that even our most powerful modern telescopes struggle to observe it directly. Rowan-Robinson argued that even a low-probability detection was worth pursuing, that it could serve as a map for where to look next.
But there was a complication. Pan-STARRS, a more sensitive survey telescope that had been operating since 2008, had scanned the same region of sky and found nothing matching the IRAS signals. Either the object had moved beyond detection range, or it had never been there at all. Rowan-Robinson did not claim to have found Planet Nine. He claimed only to have found a reason to keep looking—a thread from the past that might, if pulled, lead somewhere real. The search continues.
Citações Notáveis
The probability of the candidate being real is not overwhelming, but given the strong interest in the Planet Nine hypothesis, it would be worth checking whether an object with the proposed parameters is incompatible with observations.— Michael Rowan-Robinson, Imperial College London
A Conversa do Hearth Outra perspectiva sobre a história
Why would data from 1983 matter now, forty years later? Wouldn't a planet have moved?
Yes, it would have moved. That's actually the point. If the signal was real, we can use its position then to calculate where it should be now, and point our modern telescopes there with precision.
But Rowan-Robinson says the probability it's real is low. Why publish something unlikely?
Because in astronomy, unlikely doesn't mean impossible. And if you don't follow the thread, you'll never know. The cost of looking is small compared to the cost of missing something.
What makes this different from any other false alarm in the sky?
The specificity. Three separate detections over three months, appearing to move together. That pattern is harder to dismiss as noise, even if it probably is.
So we're back where we started—searching for a planet we can't see?
Not quite. Now we're searching with a better map. That's how discovery works sometimes. You find a clue, you follow it, and either you find what you're looking for or you learn something else.