The pulsar alternates almost continuously between two brightness states, which until recently was a great mystery. But researchers think they can now interpret this peculiar behavior.
About 4,500 light-years away in the constellation Sextant lies a pulsar — a rapidly rotating, magnetic, dead star. However, something strange is going on with this pulsar. For example, astronomers have known for some time that the enigmatic object alternates almost continuously between two different brightness states. Researchers were puzzled. But a new study now lifts a corner of the veil.
What is a Pulsar?
A pulsar is the rapidly spinning remnant of an exploded massive star. The remainder has a powerful, rotating magnetic field that generates an electric field. That electric field accelerates charged particles near the pulsar’s magnetic poles, creating a beam of radiation at both poles. Because the pulsar also rotates very quickly, the beams of radiation – just like the light beams from a lighthouse – swing through space. And when such a beam of radiation is briefly aimed at the Earth, it can be detected by astronomers. The result is a short, visible flash, making it look like the star is pulsating.
The pulsar in question, also known as PSR J1023+0038 (or J1023 for short), orbits another star. Over the past ten years, the pulsar has already ‘stolen’ a lot of matter from its companion. This matter accumulates in a disk around the dead star.
Two modes
But now comes the crazy. Once the pulsar began collecting this matter, the whirling beam of electromagnetic radiation almost completely disappeared. The pulsar then alternates between two different modes. In “high” mode, the pulsar emits bright X-rays, ultraviolet and visible light. In the ‘low’ mode, the dead star is weaker at these wavelengths and, on the other hand, emits more radio waves. The pulsar hangs in each mode for a few seconds or minutes and then switches to the other mode in just a few seconds.
Twelve (!) telescopes
Until recently, astronomers had no explanation for this puzzling behavior of J1023. To be able to interpret this, a new research team enlisted the help of no less than twelve different advanced ground and space telescopes. These included ESOs Very Large Telescope (VLT) one New Technology Telescope (NTT) involved, which detect visible and near-infrared light, as well as the Atacama Large Millimeter/submillimeter Array (ALMA). All telescopes recorded more than 280 switches between high and low mode over two nights in June 2021.
Statement
After analyzing the collected data, the team believes they can now explain J1023’s strange behavior. “We found that the mode switch stems from a complex interplay between the pulsar wind — a stream of high-energy particles that blows away from the pulsar — and matter flowing toward the pulsar,” said co-author Coti Zelati.
Material
That’s right. In low mode, matter flowing toward the pulsar is ejected in a narrow beam perpendicular to the aforementioned disk. Gradually, this matter accumulates closer and closer to the pulsar. It then collides with the wind blowing away from the pulsating star, causing the matter to heat up. The system then switches to high mode and is a bright source of X-rays, ultraviolet rays and visible light. Eventually, the blobs of hot matter are blown away by the pulsar’s whipping beam. With less hot matter in the disk, the star system glows less brightly and switches back to low mode.
This animation shows how J1023 ‘steals’ gas from its companion star. This gas accumulates in a disk around the pulsar, falls slowly towards it and is finally ejected as a narrow beam. In addition, a wind of particles blows away from the pulsar, represented here by a cloud of tiny dots. This wind collides with the incoming gas and heats it, making the star system a bright source of X-rays, ultraviolet and visible light. Eventually blobs of this hot gas are expelled from the beam and the pulsar returns to its original, weaker state, then the cycle repeats. Observations have shown that this pulsar switches between these two states every few seconds or minutes.
Expel
So, in short, J1023’s remarkable switches are the result of sudden, short-lived matter ejections. “We have witnessed extraordinary cosmic phenomena in which huge amounts of matter, similar to cosmic cannonballs, are launched into space within a very short span of tens of seconds by a small, compact celestial body spinning at incredibly high speeds,” said researcher Maria Cristina. Baglio.
The study proves once again that the expression ‘two know more than one’ – or in the case of twelve – is absolutely correct. Because thanks to the help of a dozen telescopes, astronomers have been able to explain the strange behavior of J1023. Despite the mystery being solved, the researchers keep their telescopes focused on the unique star system. Especially ESOs Extremely Large Telescope (ELT), currently under construction in Chile, will be able to provide more insight into J1023’s switchovers. “With the ELT, we can learn more about how the mode switching affects the density, distribution, dynamics and energy balance of the inflowing matter around the pulsar,” said Sergio Campana.
2023-08-31 15:01:34
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