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Simultaneous X-ray and multiband radio light curves for 4U1728. credit: Nature (2024). DOI: 10.1038/s41586-024-07133-5
How fast can a neutron star send a powerful jet into space? As our team just revealed in a paper, the answer is about one-third the speed of light. It turns out. new research was announced on Nature.
energetic cosmic beam known as Jet Found throughout our universe. These are fired when material (mainly dust and gas) falls toward a dense central object, such as a neutron star (the very dense remains of a once massive star) or a star. Black Hole.
The jet carries away some of the gravitational energy released by the falling gas and recycles it into its surroundings on a much larger scale.
The most powerful jets in the universe originate from the largest black holes at the centers of galaxies. The energy output of these jets can influence the evolution of entire galaxies and even galaxy clusters. This makes jets an important and interesting component of our universe.
Jet aircraft are common, but how they are launched is still not fully understood. Valuable information can now be obtained by measuring jets from neutron stars.
jet from star corpse
Jets from black holes tend to be bright and are well studied. But jets from neutron stars are usually much fainter, and little is known about them.
This poses a problem because we can learn a lot by comparing jets fired from different celestial bodies. neutron star Very dense stellar remains, cosmic cinders the size of a city but containing the mass of a star. They can be thought of as giant atomic nuclei, about 20 kilometers in diameter.
In contrast to black holes, neutron stars have both a solid surface and a magnetic field, and gas falling into them does not release much gravitational energy. Studying neutron star jets is especially valuable because all of these properties influence how the jets are launched.
One important clue to how a jet launches comes from its speed. Determining how the jet speed varies with the mass and spin of the neutron star would be a powerful test of theoretical predictions. However, it is extremely difficult to measure jet speed with sufficient precision for such tests.
space speed camera
When you measure speed on Earth, you measure the speed of an object between two points. This includes his 100 meter sprinters running down the track and his point-to-point speed cameras tracking cars.
Our team, led by Thomas Russell, Italian National Institute of Astrophysics In Palermo, they conducted a new experiment to do this for neutron star jets.
The reason this measurement has been so difficult until now is because the jet is a steady flow. This means there is no single starting point for the timer. However, we were able to identify a short-lived signal at X-ray wavelengths that could be used as a “starter gun.”
Neutron stars are so dense that they can “steal” material from nearby orbiting companion stars. Some of that gas is ejected outward as jets, but most ends up falling into the neutron star. When materials pile up, their temperature increases and their density increases.
When enough material accumulates, a thermonuclear explosion is triggered. A runaway nuclear fusion reaction occurs, rapidly expanding and engulfing the entire star. Fusion is short-lived, lasting from seconds to minutes. burst of x-rays.
One step closer to solving the mystery
We thought this thermonuclear explosion would disrupt the neutron star’s jet. So we used CSIRO. Australian Telescope Compact Array For three days, he stared at the jet at radio wavelengths, trying to capture the chaos.At the same time, the European Space Agency integral Use a telescope to observe the X-rays from the system.
For more information:
Thomas D. Russell et al., Thermonuclear explosions in neutron stars reveal jet velocities, Nature (2024). DOI: 10.1038/s41586-024-07133-5
