In a recent study published in Nature magazine, scientists have achieved a groundbreaking feat by accurately measuring the speed of jets emitted by neutron stars, which can reach speeds of about one third of the speed of light. These cosmic jets form when material, primarily consisting of dust and gas, falls onto dense central objects like neutron stars or black holes, and is propelled back into space, carrying away gravitational energy in the process.
While these jets are observed across the universe and play a vital role in galaxy evolution, the exact mechanism behind their formation has long puzzled scientists. By focusing on neutron star jets, which are less studied compared to black hole jets, researchers hope to shed light on this mysterious process. Neutron stars are incredibly dense remnants of stars, comparable in size to a city but with a mass equivalent to that of a star, essentially giant atomic nuclei.
Utilizing an innovative method likened to space radar for measuring speed, a team led by Thomas Russell from the Italian National Institute for Astrophysics in Palermo successfully determined the speed of neutron star jets. By observing short bursts in the X-ray spectrum resulting from thermonuclear explosions on the neutron star’s surface, the researchers could pinpoint the moment when the jets were launched, comparable to a “starting gun” in a race.
To their surprise, the researchers found that after each burst, the jets grew brighter, indicating that the thermonuclear explosions likely enhance rather than disrupt the jets. This revelation suggests that X-ray bursts accelerate the infall of gas onto a neutron star, providing additional energy to fuel the jets.
Of particular interest is the finding that the measured jet speed closely aligns with the “escape velocity” of a neutron star, which is 11.2 km/s on Earth and approximately half the speed of light for a neutron star. This study not only advances our understanding of the mechanisms behind launching cosmic jets but also introduces new techniques for measuring their speed, marking a significant step towards unraveling the universe’s mysteries.