Scientists using the H.E.S.S. observatory in Namibia have detected gamma rays from a pulsar (a type of dead star) with energy levels unlike anything we’ve seen before. These gamma rays possess energy that’s roughly ten trillion times that of visible light.
The perplexing findings, which appear in the journal Nature Astronomy, challenge existing theories held by scientists.
What’s a Pulsar?
A pulsar is essentially a stellar corpse left behind after a star erupts in a brilliant explosion known as a supernova. These remnants are surprisingly tiny, with a diameter of only about 20 kilometers.
Despite their small size, pulsars are astonishingly dense. To give a sense of their incredible density, consider this: “A teaspoon of their material has a mass of more than five billion tonnes, or about 900 times the mass of the Great Pyramid of Giza,” elaborates H.E.S.S. scientist Emma de Oña Wilhelmi in a statement. These stars rotate at an incredibly rapid pace and have a strong magnetic field.
Like cosmic lighthouses, pulsars emit rotating beams of electromagnetic radiation. When these beams sweep across our solar system, we observe periodic flashes of radiation. The source of this radiation, scientists believe, stems from fast electrons moving in the pulsar’s surrounding magnetic field, known as the magnetosphere.
“On their outward journey, the electrons acquire energy and release it in the form of the observed radiation beams,” says Bronek Rudak from the Nicolaus Copernicus Astronomical Center in Poland.
Vela’s Bright Surprise
The Vela pulsar, nestled in the Vela constellation, stands out as the brightest pulsar in both the radio band and the gamma rays’ giga-electronvolts (GeV) range. Remarkably, it rotates about eleven times every second.
Previously, it was believed that the radiation from the Vela pulsar ended abruptly at a certain point. However, with the H.E.S.S. observatory’s advanced capabilities, researchers detected a new radiation component with energies scaling up to tens of tera-electronvolts (TeV). “That is about 200 times more energetic than all radiation ever detected before from this object,” says co-author Christo Venter, from North-West University in South Africa.
Challenging Old Ideas
The astonishing findings don’t just stop at the discovery of high-energy gamma rays; they also raise questions about our understanding of pulsars.
“The traditional scheme according to which particles are accelerated along magnetic field lines within or slightly outside the magnetosphere cannot sufficiently explain our observations,” says lead researcher Arache Djannati-Atai, from the Astroparticle & Cosmology (APC) laboratory in France. “Theories involving magnetic reconnection beyond the light cylinder are being explored, but even these have complications.
This discovery positions the Vela pulsar as the holder of the record for the highest-energy gamma rays ever discovered. Beyond this accolade, the find is significant for the future. “This discovery opens a new observation window for detection of other pulsars… paving the way for a better understanding of the extreme acceleration processes in highly magnetised astrophysical objects,” says Djannati-Atai.
For the average person, this might sound like a lot of complex science, but in simpler terms: imagine stumbling upon an entirely new shade of a color you thought you knew inside out. This discovery is a testament to the ever-unfolding mysteries of our universe and how much more there is left to explore and understand.