Scientists at the H.E.S.S. observatory in Namibia have identified extraordinarily high-energy gamma rays emanating from the Vela pulsar, leading to questions about existing models concerning the emission of pulsed gamma rays from such celestial bodies. The observed gamma rays have energy levels that exceed previous records for the Vela pulsar by a factor of 200, necessitating a reevaluation of the underlying processes responsible for these potent emissions.
The H.E.S.S. observatory measured gamma rays with energy levels of 20 tera-electronvolts emanating from the Vela pulsar.
Researchers operating the H.E.S.S. observatory in Namibia have recorded the most energetic gamma rays ever detected from a pulsar, a type of dead star. These gamma rays exhibit energies of 20 tera-electronvolts, which is roughly ten trillion times greater than the energy of visible light. These findings, reported today (October 5) in the scientific journal Nature Astronomy, pose significant challenges to the prevailing theories regarding the generation of such pulsed gamma rays.
Understanding the Properties of Pulsars
Pulsars are the residual cores of stars that have undergone cataclysmic supernova explosions. These remnants are extremely compact, with a diameter of about 20 kilometers, and possess a tremendously strong magnetic field. They are largely comprised of neutrons and exhibit extraordinary density: a single teaspoon of their material would weigh over five billion tonnes, approximately 900 times the mass of the Great Pyramid of Giza, notes Emma de Oña Wilhelmi, a H.E.S.S. scientist and co-author of the study, who is affiliated with DESY.
Origin of Pulsar Radiation
Pulsars radiate oscillating beams of electromagnetic radiation, operating much like celestial lighthouses. When these beams intersect with our solar system, we detect periodic bursts of radiation. Researchers postulate that high-velocity electrons generated and accelerated within the pulsar’s magnetosphere are the sources of this radiation. The magnetosphere consists of a combination of plasma and electromagnetic fields that rotate in conjunction with the star. “As these electrons move towards the outer regions, they gain energy and subsequently emit it as the observed beams of radiation,” explains Bronek Rudak from the Nicolaus Copernicus Astronomical Center (CAMK PAN) in Poland, another co-author of the study.
The Vela pulsar is notably the most luminous pulsar in the radio frequency range of the electromagnetic spectrum and is a leading source of cosmic gamma rays in the giga-electronvolts (GeV) domain. It completes approximately eleven rotations per second. However, its radiation ceases abruptly at energies beyond a few GeV, likely because the electrons reach the boundary of the magnetosphere and exit it.
A New Frontier in Pulsar Research
Further analysis using the H.E.S.S. observatory revealed an additional radiation component with energies reaching up to tens of tera-electronvolts (TeV). “The energy levels detected are about 200 times greater than any previously recorded radiation from this object,” states Christo Venter from North-West University in South Africa, a co-author of the study. This high-energy component manifests at the same intervals as the GeV-range emissions, but its origins are unclear and may require electrons to journey even beyond the magnetosphere, while maintaining the established rotational emission pattern.
“The findings challenge existing conceptions of pulsars and mandate a review of how these natural cosmic accelerators function,” declares Arache Djannati-Atai from the Astroparticle & Cosmology (APC) laboratory in France, the study’s lead researcher.
“Our conventional understanding, which proposes that particles are accelerated along the magnetic field lines within or just outside the magnetosphere, fails to adequately account for our observations. We may be observing particle acceleration via magnetic reconnection beyond the light cylinder, yet this hypothesis also encounters challenges in explaining the production of such intense radiation.”
In light of these discoveries, the Vela pulsar now holds the distinction of emitting the highest-energy gamma rays ever discovered. “This breakthrough offers a new avenue for the detection of other pulsars in the tens of tera-electronvolt range using current and forthcoming more sensitive gamma-ray telescopes, thus providing insights into the extreme acceleration phenomena in highly magnetized astrophysical entities,” concludes Djannati-Atai.
Reference: “Discovery of a Radiation Component from the Vela Pulsar Reaching 20 Teraelectronvolts,” published on October 5, 2023, in Nature Astronomy.
Frequently Asked Questions (FAQs) about Vela pulsar gamma rays
What is the main discovery reported in the article?
The article reports on the discovery of exceptionally high-energy gamma rays emanating from the Vela pulsar. These gamma rays have energy levels that are approximately 200 times greater than any previously observed from this pulsar.
Where was this discovery made?
The discovery was made using the H.E.S.S. observatory located in Namibia.
Why is this discovery significant?
The discovery is significant because it challenges existing theories about pulsed gamma rays emitted from pulsars. The energy levels observed are difficult to reconcile with current scientific understanding, necessitating a reevaluation of the mechanisms responsible for such powerful emissions.
What is a pulsar?
A pulsar is a highly magnetized, rotating neutron star that emits beams of electromagnetic radiation. It is essentially the leftover core of a star that has exploded in a supernova.
What are the properties of the Vela pulsar?
The Vela pulsar is particularly notable for being the brightest pulsar in the radio frequency range of the electromagnetic spectrum. It is also a prominent source of cosmic gamma rays in the giga-electronvolt (GeV) domain. The pulsar rotates approximately eleven times per second.
How do scientists think pulsars emit radiation?
Scientists believe that high-velocity electrons generated and accelerated within a pulsar’s magnetosphere are the sources of its radiation. These electrons gain energy as they move towards the outer regions of the magnetosphere, emitting it as beams of radiation.
What are the theoretical implications of this discovery?
The findings challenge our current understanding of how pulsars work as natural cosmic accelerators. Existing theories that propose particles are accelerated along magnetic field lines within or just outside the magnetosphere fail to adequately explain the observations.
What future research does the discovery pave the way for?
The discovery opens a new observation window for the detection of other pulsars in the tens of tera-electronvolt range using more sensitive gamma-ray telescopes. This could lead to a better understanding of extreme acceleration processes in highly magnetized astrophysical objects.
More about Vela pulsar gamma rays
- H.E.S.S. Observatory Overview
- Nature Astronomy Journal
- Introduction to Pulsars
- Understanding Gamma Rays
- The Vela Pulsar
- The Phenomenon of Magnetic Reconnection
- The Nicolaus Copernicus Astronomical Center (CAMK PAN)
- Astroparticle & Cosmology (APC) Laboratory
- North-West University Research Publications