2024-02-19 13:15:23
What is causing mysterious fast bursts of radio waves at distant points in the cosmos? Thanks to recent research, the enigma seems to be one step closer to being clarified.
Although they only last a fraction of a second, fast bursts of radio waves can release as much energy as the Sun in a year. In addition, their light forms a beam comparable to a laser that distinguishes them from the most common cosmic explosions.
Because they are so brief, it is often difficult to determine their origin. Before 2020, those that had been traced to their source originated outside our galaxy, too far away for astronomers to see what created them. Then a rapid burst of radio waves emerged in our galaxy, originating from an extremely dense object called a magnetar, a type of neutron star. Neutron stars are compressed corpses of an exploded star.
In October 2022, the same magnetar, called SGR 1935+2154, produced another fast burst of radio waves. On this occasion, two X-ray space telescopes observed what appears to be part of the phenomenon. Just minutes before and after the rapid burst of radio waves, they picked up anomalous X-ray readings.
One of these telescopes was the NICER (Neutron Star Interior Composition Explorer) on board the International Space Station. The other was the NuSTAR (Nuclear Spectroscopic Telescope Array) in Earth orbit. Both telescopes observed the magnetar for hours, glimpsing what happened on the surface of the source object and in its immediate surroundings, before and after the rapid burst of radio waves.
The burst occurred between two changes in the magnetar’s rotation speed. It happened after the magnetar suddenly started spinning faster. SGR 1935+2154 is estimated to be about 20 kilometers in diameter and rotates about 3.2 times per second, meaning that its surface was moving at about 11,000 km/h.
Slowing down or speeding up the rotation of such a dense star requires a significant amount of energy. Therefore, the authors of the study were surprised to see that, after the increase in speed, the magnetar slowed down to a speed lower than what it had before its abrupt increase in speed. The decrease in speed occurred in just nine hours, that is, about 100 times faster than previously observed in a magnetar.
Normally, when such changes in speed occur in a magnetar, it takes weeks or months for it to recover to its normal speed, as argued by Chin-Ping Hu, of the National Changhua University of Education in Taiwan and a member of the research team. This, however, did not happen with SGR 1935+2154.
To figure out how magnetars produce fast bursts of radio waves, there are many variables to consider.
For example, magnetars (which are a type of neutron star) are so dense that a teaspoon of their material would weigh about a billion tons on Earth. Such a high density also implies a strong gravitational attraction: A marshmallow falling on a typical neutron star would impact with the force of an atomic bomb.
Shortly before the fast burst of radio waves of 2022, the magnetar began releasing bursts of X-rays as well as gamma rays (even more energetic wavelengths of light) that were observed in the peripheral vision of telescopes. high energy space. This increase in activity led telescope managers to point NICER and NuSTAR directly at the magnetar.
All those bursts of from Maryland in the United States and member of the research team. “So it appears that something changed during the slowdown period, creating the right set of conditions for the gust to occur.”
What else could have happened to SGR 1935+2154 to produce a fast burst of radio waves? One factor could be that the exterior of a magnetar is solid, and the high density crushes the interior into a state called superfluid. Occasionally, both (exterior and interior) can become out of sync, like water jumping chaotically inside a rotating fish tank. When this occurs, the fluid can supply energy to the crust. The study authors believe this is what likely caused the two abrupt rotational speed changes that accompanied the rapid burst of radio waves.
If the initial change in rotation speed caused a crack in the surface of the magnetar, material from inside the magnetar could have been released through the crack into space, like a volcanic eruption. The loss of mass causes rotating objects to slow down, so the researchers believe this could explain the rapid slowing of the magnetar’s rotation.
Artistic recreation of a magnetar losing material in space, in an ejection that would have caused its rotation to slow down. The magnetar’s strong, twisted magnetic field lines (in green) can influence the flow of electrically charged material from the object. (Image: NASA JPL/Caltech)
However, having observed only one of these phenomena in real time, the team cannot yet say which of these factors (or others, such as the magnetar’s powerful magnetic field) could lead to the production of a rapid burst of radio waves. .
As George Younes, a researcher at NASA’s Goddard Space Flight Center and co-author of the study, points out, the findings made in the new study constitute an important clue to clarify the enigma of the origin of fast bursts of radio waves, but still Much more data is needed to achieve this. (Source: NCYT from Amazings)
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