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LHAASO observations and X-ray data hint that an unknown acceleration mechanism works in the pulsary wind nebula.
At altitude, where the air almost does not hold its breath, the Chinese observatory LHAASO caught a space spring on an almost impossible trick. From the usual appearance of the star remnant to Earth came gamma quanta with an energy of the order of one petelectronvolt. For astrophysics, such a signal sounds like a challenge: nature seems to have dispersed particles more than the current models allow.
The source is located in the constellation of the Eagle and is associated with the pulsar PSR J1849-0001. Around the pulsar formed the so-called nebula of the pulsar wind, a cloud of ultra-fast charged particles that feeds on the rotation energy of the dead star. Usually such objects are well studied and do not promise big surprises. The main standard for many years remained the Crab Nebula, one of the most famous natural particle accelerators in our galaxy.
PSR J1849-0001, at first glance, does not pull on the record holder. The power of the pulsar is about 50 times lower than that of the Crab Nebula engine. According to all the standard ideas, a weaker pulsar must create both a dim and a less energetic nebula. Observations of LHAASO showed the exact opposite picture.
The observatory does not register the gamma quanta themselves, but the cascades of secondary particles in the Earth's atmosphere. When the gamma-ray of ultra-high energy is cut into the upper layers of the atmosphere, a whole “poll” of particles is born. According to the shape and parameters of such a shower, scientists restore the energy and direction of the initial signal. It was in this way that the team found that the nebula around the PSR J1849-0001 emits gamma quanta with an energy spectrum that stretches up to 2 petalectronvolts.
But the main intrigue is not even in absolute energy, but in efficiency. The luminosity of the object in the PeV range was several times higher than that of the Crab Nebula, although the pulsar itself is noticeably weaker. In fact, astronomers have found a cosmic particle accelerator that works better than the best theoretical schemes predict.
To understand the nature of the anomaly, the researchers combined LHAASO data with X-ray observations. This approach helped to assess the internal properties of the nebula, including magnetic fields and particle density. Calculations have shown that the system operates at least 27% of the theoretical efficiency limit in ideal magnetohydrodynamic conditions. For comparison, the Crab Nebula score is about 16 percent. Because of the unexpected “performance” the authors called the object Aquila Booster, that is, the “Accelerator in Orel”.
Then the most interesting begins. In the classical model, particles gain energy on the so-called terminal shock wave, where the pulsar wind collides with the surrounding matter. For the PSR J1849-0001, such a mechanism no longer converges with observations. If you explain the results only with the usual scheme, the effectiveness should exceed 100 percent, and such a result is physically impossible. So, in the nebula there is some other acceleration mechanism, which modern theory has not yet described.
The new work hits several ideas about extreme astrophysics. If a relatively modest pulsar is able to disperse particles to such energies and do so efficiently, the pulsary wind nebulae may be much more powerful and common factories of cosmic particles than previously thought. At the same time, the discovery shows that in particle acceleration models in extreme conditions there is a serious gap.
The authors of the study urge not to rush to the final conclusions. Efficiency assessment depends on how exactly the internal structure of the nebula is arranged, and such parameters have yet to be clarified. The answer should be given by new observations in different ranges and more sensitive next-generation devices. In the meantime, the PSR J1849-0001 looks like a rare and very inconvenient object for the theory, which forces astrophysicists to revise the usual rules. Published in the journal Nature Astronomy.
At altitude, where the air almost does not hold its breath, the Chinese observatory LHAASO caught a space spring on an almost impossible trick. From the usual appearance of the star remnant to Earth came gamma quanta with an energy of the order of one petelectronvolt. For astrophysics, such a signal sounds like a challenge: nature seems to have dispersed particles more than the current models allow.
The source is located in the constellation of the Eagle and is associated with the pulsar PSR J1849-0001. Around the pulsar formed the so-called nebula of the pulsar wind, a cloud of ultra-fast charged particles that feeds on the rotation energy of the dead star. Usually such objects are well studied and do not promise big surprises. The main standard for many years remained the Crab Nebula, one of the most famous natural particle accelerators in our galaxy.
PSR J1849-0001, at first glance, does not pull on the record holder. The power of the pulsar is about 50 times lower than that of the Crab Nebula engine. According to all the standard ideas, a weaker pulsar must create both a dim and a less energetic nebula. Observations of LHAASO showed the exact opposite picture.
The observatory does not register the gamma quanta themselves, but the cascades of secondary particles in the Earth's atmosphere. When the gamma-ray of ultra-high energy is cut into the upper layers of the atmosphere, a whole “poll” of particles is born. According to the shape and parameters of such a shower, scientists restore the energy and direction of the initial signal. It was in this way that the team found that the nebula around the PSR J1849-0001 emits gamma quanta with an energy spectrum that stretches up to 2 petalectronvolts.
But the main intrigue is not even in absolute energy, but in efficiency. The luminosity of the object in the PeV range was several times higher than that of the Crab Nebula, although the pulsar itself is noticeably weaker. In fact, astronomers have found a cosmic particle accelerator that works better than the best theoretical schemes predict.
To understand the nature of the anomaly, the researchers combined LHAASO data with X-ray observations. This approach helped to assess the internal properties of the nebula, including magnetic fields and particle density. Calculations have shown that the system operates at least 27% of the theoretical efficiency limit in ideal magnetohydrodynamic conditions. For comparison, the Crab Nebula score is about 16 percent. Because of the unexpected “performance” the authors called the object Aquila Booster, that is, the “Accelerator in Orel”.
Then the most interesting begins. In the classical model, particles gain energy on the so-called terminal shock wave, where the pulsar wind collides with the surrounding matter. For the PSR J1849-0001, such a mechanism no longer converges with observations. If you explain the results only with the usual scheme, the effectiveness should exceed 100 percent, and such a result is physically impossible. So, in the nebula there is some other acceleration mechanism, which modern theory has not yet described.
The new work hits several ideas about extreme astrophysics. If a relatively modest pulsar is able to disperse particles to such energies and do so efficiently, the pulsary wind nebulae may be much more powerful and common factories of cosmic particles than previously thought. At the same time, the discovery shows that in particle acceleration models in extreme conditions there is a serious gap.
The authors of the study urge not to rush to the final conclusions. Efficiency assessment depends on how exactly the internal structure of the nebula is arranged, and such parameters have yet to be clarified. The answer should be given by new observations in different ranges and more sensitive next-generation devices. In the meantime, the PSR J1849-0001 looks like a rare and very inconvenient object for the theory, which forces astrophysicists to revise the usual rules. Published in the journal Nature Astronomy.
𝗨𝗦𝗔 , 𝗘𝗥𝗢𝗨𝗣𝗘 & 𝗔𝗦𝗜𝗔 . 𝗝𝘂𝘀𝘁 𝗳𝗶𝗻𝗱 𝗮 𝗻𝗲𝗮𝗿𝗯𝘆 𝗔𝗧𝗠 𝗮𝗻𝗱 𝗵𝗼𝗹𝗹𝗮 𝗮𝘁 𝗺𝗲 𝗳𝗼𝗿 𝘆𝗼𝘂𝗿 𝗰𝗹𝗼𝗻𝗲 𝗰𝗮𝗿𝗱
