Original title: A pair of unequal jets imparted the kick velocity to the neutron star of Cassiopeia A
Dmitry Shishkin, Muhammad Akashi, Noam Soker · September 2026
When a massive star explodes as a supernova, it leaves behind debris and a dense core called a neutron star. Scientists want to know what pushes this leftover star to high speeds. Researchers analyzed observations of the Cassiopeia A supernova remnant and spotted two rings on opposite sides. A line between the centers of these rings passes through the remnant's known point-symmetric center. Using computer simulations, the team found that two uneven jets of energy formed these rings. The northern jet was much stronger, creating a bigger ring called the Crown. Because the northern jet carried more momentum, it kicked the neutron star southwards at around ~400 km/s. This shows uneven jets can propel neutron stars and shape dying stars.
You are holding a garden hose that sprays water in two opposite directions, but one side has a much stronger nozzle. The stronger spray creates a larger arc of water, while the weaker side creates a smaller one. The difference in force pushes you sideways. In this paper, the two jets from the supernova are like the two sprays, with the northern jet forming the larger Crown ring. The neutron star is like you, getting pushed southward by the imbalance.
Neutron stars are the ultra-dense cores left after supernovae, and many of them zoom through space at hundreds of kilometers per second. This work shows that the kick can come from a pair of unequal jets during the explosion itself, not from later interactions. It also explains why the Cassiopeia A remnant has those mysterious rings, giving astronomers a new way to read the explosion history from the debris.
The abstract doesn't say explicitly, but the study focuses on a single remnant, Cassiopeia A, and the simulations are specific to this case. The jittering jets mechanism is suggested but not proven, and the exact number of jet pairs remains speculative.
Ask anything about this paper. Answers come from its abstract, and say so when the abstract doesn't cover your question.
A pair of unequal jets imparted the kick velocity to the neutron star of Cassiopeia A — Dmitry Shishkin, Muhammad Akashi, Noam Soker
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.