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An international team of astronomers has revealed new insights into an object at the heart of the cosmic puzzle – a pulsar that appears to be constantly changing in brightness. Now, scientists think they know what’s behind it.
Fast-spinning dead stars are so named because as they rotate they shoot beams of electromagnetic radiation through space that appear to pulsate like celestial beacons.
But the pulsar called PSR J1023+0038, located about 4,500 light-years from Earth in the constellation Sextans, is even more unusual in that some pulsations are brighter than others, almost as if they switch between different modes.
The spinning dead star and its closely orbiting companion star were first discovered in 2007. But new observations made with multiple telescopes show that strange things happen when the pulsar skimmes material away from the other star, and this activity has been going on for the past decade. .
A study of the new observations was published on Wednesday in the journal Astronomy and astrophysics.
“We have witnessed extraordinary cosmic events where massive amounts of matter, cosmic cannonball-like, are shot into space within a very short time of tens of seconds from a small, dense object spinning at incredibly high speeds,” said Maria, the study’s lead author. Christina Baglio, a researcher at New York University Abu Dhabi affiliated with the Italian National Institute of Astrophysics, said in a statement.
Once the pulsar began to siphon material from the companion star, its characteristic pulsar ray disappeared. Instead, the pulsar entered a constant, alternating cycle of working in what astronomers call a “high” mode and a “low” mode.
During the high mode, the pulsar emits X-rays, ultraviolet light, and visible light wavelengths. Once in the low mode, the pulsar becomes dimmer, sharing more radio waves than other wavelengths of light. Both modes can last for seconds or minutes before switching to the other.
Astronomers needed a variety of observatories that could detect different types of light to solve the celestial puzzle.
“Our unprecedented observational campaign to understand the behavior of this pulsar included dozens of advanced ground and space telescopes,” study co-author Francesco Cotti Zelati, a researcher at the Institute of Space Sciences in Barcelona, Spain, said in a statement.
In June 2021, the pulsar made more than 280 switches between high and low mode. Various telescope observations have gathered the details astronomers need to understand what happened during both modes.
They discovered that the exchange of matter between the pulsar and its companion star leads to the unusual behavior of the pulsar.
When the pulsar pulls on its companion star, gas from the companion star is released and forms a disk around the pulsar before slowly falling towards it.
Finally, in the lowered position, the same material is released from the pulsar in a narrow jet. The expelled material is exposed to the winds blowing from the pulsar. The wind heats up the stellar material, causing it to glow with different wavelengths of light, activating the high mode.
The process repeats as the jet continues to push more material away from the star, moving some of the hotter and glowing material out of the way and returning the low position.
“We discovered that the mode switching stems from a complex interaction between the pulsar wind, the flow of high-energy particles shooting away from the pulsar, and the matter flowing toward the pulsar,” said Cuti-Zelati.
Astronomers don’t know if there are other similar pulsar systems out there, or if this one is unique.
Astronomers will continue to monitor the unusual system and have plans to use future observatories, such as the European Southern Observatory’s Very Large Telescope currently being built in Chile, to get more details. The Extremely Large Telescope, or ELT, will begin observations in 2028.
“ELT will allow us to gain fundamental insights into how the abundances, distribution, dynamics and energy of matter flowing around a pulsar are affected by mode-switching behavior,” said Sergio Campana, study co-author and director of research at the Italian National Institute. The Brera Astrophysical Observatory, in a statement.
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