The behavior of a pulsar is being better understood following an observation campaign by twelve terrestrial and space telescopes, including three from the European Southern Observatory (ESO).
A pulsar is one of the celestial objects that can form after the explosion of a massive star at the end of its life. It therefore corresponds to a very magnetic and rapidly rotating dead star that emits a beam of electromagnetic radiation (like the beam from a lighthouse) that traverses space. This beam can be detected by telescopes.
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The pulsar is an object known for its changing nature, as its brightness almost constantly fluctuates between two intensities. For this reason, its brightness appears to pulsate from Earth.
This pulsation phenomenon has so far remained largely unexplained. This came before the work of Spanish researcher Francesco Coti Zelati from the Institute of Space Sciences in Barcelona and his colleagues from other institutions, who studied the pulsar J1023, discovered in 2007.
The latter have determined that sudden ejections of matter from the pulsar over very short periods of time are the cause of these strange variations, they explain in a statement published by ESO.
We have witnessed extraordinary cosmic events in which huge amounts of matter, similar to cosmic cannonballs, are ejected into space in just ten seconds from a small, dense celestial object rotating at incredibly high speeds.
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The pulsar PSR J1023+0038 (in white) is part of a binary star system that sucks in material from its companion star (in red) via an accretion disk (also in red). (Artistic illustration)
Zoom in on the strange pulsar J1023
Located about 4,500 light-years from Earth in the constellation Sextant, the J1023 pulsar (also known as PSR J1023+0038) is of particular interest to scientists. This is because it is in orbit around another star and is actively sucking in material from its companion. This material, which has accumulated in a disk shape around the pulsar, slowly falls on it.
However, since the beginning of this process of matter accumulation, which has been observed for about ten years, the beam of light has practically disappeared and the pulsar begins to constantly switch from one mode to the other.
In high mode, the pulsar emits X-rays, ultraviolet and visible light, while in low mode it is weaker at these frequencies and emits more radio waves, ESO explains, adding that the pulsar can stay in each mode for several seconds, or minutes, and switch You can then switch to the other mode in just a few seconds.
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The Pulsar PSR J1023+0038. (Artistic illustration)
For example, over two nights in June 2021, astronomers observed more than 280 changes between J1023’s high and low modes.
This change puzzled astrophysicists, but the recent observation campaign made it possible to better explain J1023’s behavior.
We found that the mode change results from a complex interaction between the pulsar wind, a stream of high-energy particles flowing away from the pulsar, and matter flowing toward the pulsar.
In low-intensity mode, material flowing toward the pulsar is ejected in a narrow jet perpendicular to the disk. Gradually, this material accumulates closer and closer to the pulsar and is then hit by the wind from the pulsating star, causing the material to heat up, ESO notes.
The system then enters high-intensity mode and emits powerful X-rays, ultraviolet and visible light. The pulsar eventually evacuates these masses of hot material via the jet.
If there is less hot material in the disc, the system will glow less brightly and will return to low intensity mode.
Still many secrets
This discovery helps explain some of J1023’s strange behavior.
But this unique pulsar still holds some secrets, which is why telescopes will continue to study it closely. And the arrival of ESO’s very powerful European Giant Telescope (TGE) by 2027 will make it possible to achieve this even more precisely.
“The TGE will allow us to understand how the abundance, distribution, dynamics and energy of matter flowing in around the pulsar are affected by mode changes,” notes Sergio Campana of the Barcelona Institute of Space Sciences, who signed this study, also published in the journal Astronomy & Astrophysics (New window) (in English).