Astronomers Can't Pinpoint the Source of the Most Powerful Source of Radiation

A thousand light years away, a pulsar known as Vela emits intense bursts of energy 11 times per second. These bursts encompass radio waves, visible light, x-rays, and gamma rays.

Astrophysicist Arache Djannati-Atai and his colleagues from the Astroparticle and Cosmology Laboratory in France, utilizing the High Energy Stereoscopic System telescope located in Namibia, have made a remarkable discovery. They have found that some of the gamma rays emitted by Vela possess far greater energy than anything previously observed by astronomers. At present, they are unable to provide a satisfactory explanation for this phenomenon.

Vela, recognized as one of the most luminous pulsars across multiple wavelengths, emits energy ranging from radio waves to gamma rays. Pulsars are remnants of deceased stars with a dense, rapidly spinning core enveloped by an immensely powerful magnetic field. Beams of radiation emanate from the pulsar's poles, and as it rotates, these beams sweep through space akin to the beams of a lighthouse. From our vantage point on Earth, the pulsar appears to shine intermittently, hence its name.

Until recently, astronomers believed that the most energetic gamma rays emitted by Vela possessed a strength of a few billion electron volts. However, Djannati-Atai and his colleagues employed a specialized telescope designed to detect highly energetic gamma rays with short wavelengths, leading them to the discovery that Vela is emitting gamma rays with an astonishing energy of 20 trillion electron volts.

In order to comprehend the context, it is necessary to delve briefly into the physics involved. Light, including all types of radiation, consists of particles known as photons. The brightness of a source is determined by the quantity of photons observed, while each individual photon carries a specific amount of energy. Photons with higher energy possess shorter wavelengths. This can be visualized by imagining an energetic photon vigorously oscillating, while a lower-energy photon moves languidly in gentle undulations.

While gamma rays are already recognized as the most energetic form of radiation, certain gamma rays possess more energy than others. The previous energy record was held by a gamma ray burst originating from a massive star's collapse into a black hole, an event astronomers detected in late previous year. Each photon released during this event carried an energy of 18 trillion electron volts. This achievement was truly impressive, considering that gamma ray bursts are generally only capable of carrying a few billion electron volts, making last year's record-breaking incident at least a thousand times more powerful than the norm.

And now we have Vela, emitting gamma rays from its poles with an astounding energy of 20 trillion electron volts, as it whirls frantically on its axis and flashes towards us every 11 seconds. Though astrophysicists are actively investigating the cause of this occurrence, they have not yet comprehensively understood why Vela emits such highly energetic gamma rays.

The magnetic field of a pulsar is essentially an immensely powerful version of the particle accelerators found at SLAC or the Large Hadron Collider. Electrons are propelled along the lines of the magnetic field, attaining incredible speeds before being expelled into space through jets located at the pulsar's north and south poles. During this process, these high-speed electrons release vast amounts of energy, generating the pulsar's rotating beams of light.

However, there is a conundrum. Based on existing knowledge about Vela's magnetic field, its rotational speed, and the velocity and strength of its particle jets, it should not be possible for the electrons to achieve the requisite speed to emit gamma rays with 20 trillion electron volts of energy. Employing mechanical terms, the length of the particle accelerator is inadequate for such a phenomenon to occur.

This suggests the existence of another factor, beyond the particle jets, responsible for generating these super-energetic gamma rays. Djannati-Atai and his colleagues propose the possibility of a process occurring within the magnetic field, either beyond the end of the jets or related to the pulsar's powerful winds. However, neither of these scenarios completely elucidates the observations. To date, no hypothesis conceived by the researchers can account for radiation possessing such a high energy level. Moreover, the energetic gamma rays appear to be connected to the jets, as they flash at the same frequency of 11 times per second, correlating with the other forms of radiation emitted by Vela.

The only way to decipher this cosmic puzzle is to conduct further scientific investigations. Astronomers have recently detected an astronomical phenomenon predicted by Albert Einstein, whom we believed would remain unseen. This discovery represents just one of many similar phenomena observed thus far.

The four light blue spots encircling the small orange object in an image captured by the Very Large Telescope, known as VLT for short, are, in actuality, four images of the same galaxy. These images are projected through a gravitational lens, forming a rare arrangement known as an Einstein cross.

Astronomers employ gravitationally lensed images such as these to observe galaxies that would otherwise be too distant and faint to detect. In this particular instance, the light stemming from the small blue galaxy dates back 11 billion years.

Eminent physicist and renowned fashion icon, Albert Einstein, anticipated the existence of gravitational lenses within his theory of general relativity. Another physicist postulated that if Earth, the gravitational lens, and a distant object were perfectly aligned, the distant object would be transformed by the gravitational lens.