A whirling, strongly magnetic neutron star about 1,000 light-years away is so dense that a tablespoon of it is equivalent to the weight of Mount Everest. To say the least, it’s an intense sight, which is why astronomers naturally enjoy studying it. The Vela Pulsar is a name you’ve probably heard before.
Scientists reported on Thursday (Oct. 5) that data from Namibia’s High Energy Stereoscopic System (HESS) observatory indicated that this cosmic marvel has just become a little more marvelous. Vela appears to have released the highest-energy radiation yet seen from a pulsar.
This object appears to have ejected gamma-ray photons of at least 20 teraelectronvolts (TeV), or 20 trillion electronvolts, which are associated with wavelengths that convey the highest energy of all electromagnetic spectrum waves. 1 electronvolt is the amount of energy gained by a single electron after being accelerated by one volt of electricity.)
To put it into perspective, Arache Djannati-Ata, discovery team lead and scientist at France’s Astroparticle & Cosmology laboratory, estimates that it would take approximately 2,000,000 normal solar flare photons to produce one 20 TeV photon. “When compared to visible light,” Djannati-Ata told Space.com, “about 2×1013 visible photons are required.”
Despite the fact that Vela is a very “normal” pulsar, with rotations occurring 11 times per second, the researcher explains that it’s an important issue in astronomy because it’s quite close to us — cosmically speaking, that is.
Pulsars are often predicted to release radiation with energy less than tens of gigaelectronvolts (GeV), much alone TeVs. One gigaelectronvolt equals one billion electronvolts.
According to the scientists, although Vela first demonstrated a sort of cutoff in terms of radiation emissions — in fact, even while certain theoretical projections suggested Vela may emit in the TeV region, no one predicted the astonishing 20 TeV figure the researchers managed to discover.
“We had searched for a pulsed emission from Vela at lower energies,” Djannati-Ataï added, “But detecting photons reaching 20 TeV was really a surprise.” The only other pulsar known to have TeV-level emissions is the Crab Pulsar, which is located more than 6,000 light-years from Earth — yet even that pulsar’s radiation only reached roughly 1 TeV.
Finally, before we go into the ramifications of this high-energy observation, there is one more exciting discovery regarding Vela to address.
The team discovered that Vela’s very intense photons related to a previously unknown spectrum component of pulsars. The term “spectrum” refers to a diagram that depicts all of the varied light intensities and energy released by a pulsar. (This is not exclusive to pulsars. As long as there remains light, scientists can examine a wide range of cosmic entity spectrum.
So, with Vela’s spectrum, the scientists discovered a rapidly rising trend and a distinct separation between TeV emissions and lower-level emissions. This suggests that the very energetic photons couldn’t have been a continuation of lower energy photons, growing and growing (and growing) until they reached TeV level.
“This is in contrast to the Crab Pulsar,” Djannati-Ata remarked, whose energy spectrum continues to emit GeVs.
What does this mean for astronomy in general? For starters, it teaches us a lot about one of the most remarkable objects in our universe.
“Within the zoo of cosmic objects, pulsars are fantastic,” said Djannati-Ata. “They are cosmic laboratories with incredible features that we cannot reach, by far, on Earth.”
The creation story of pulsars is also extremely fascinating. They are the spinning carcasses of stars that once died in a supernova explosion. They are virtually entirely composed of neutrons and emit radiation beams that occasionally sweep over our solar system. These sweeps, which occur at regular time intervals, allow scientists to map out the spectra of these things.
This extremeness is also why scientists investigate the space around pulsars to test major physics principles, as Djannati-Ata mentions when referring to them as “cosmic laboratories.” Experts are particularly interested in whether Albert Einstein’s theory of general relativity applies to pulsars since these objects are among the most gravitationally intense in the cosmos — and general relativity offers a mind-bending explanation for gravity itself. As far as we know, it serves that purpose.
Furthermore, Djannati-Ata claims that these discoveries place strict restrictions on our knowledge of the source of pulsar radiation. Scientists currently assume that the source is fast-moving electrons created and accelerated in the pulsar’s magnetosphere and traveling toward the object’s edge. This hypothesis, however, does not fully explain the team’s results; other events must occur in order to produce emissions with energies as high as 20 TeV.
And, while the researchers have some theories, they plan to complete the mystery with future data. For the time being, we can rejoice in the fact that these findings have formally paved the way for scientists working among the stars.
