A team of astronomers has uncovered the secret behind the bizarre behavior of a dead star that is devouring its companion and shooting out balls of matter into space.
The star, known as PSR J1023+0038 or J1023 for short, is a pulsar, a type of neutron star that spins rapidly and emits beams of radiation from its poles. The pulsar is part of a binary system, orbiting a low-mass star that is being stripped of its gas by the pulsar’s strong gravity.
The astronomers, led by Maria Cristina Baglio from New York University, Abu Dhabi, published their findings in The Astrophysical Journal1. They used data from several telescopes, including NASA’s Neil Gehrels Swift Observatory and the European Space Agency’s XMM-Newton, to study the pulsar’s changing brightness. They found that the pulsar switches between two modes: a low mode when it emits mostly radio waves, and a high mode when it emits mostly X-rays.
The researchers discovered that the pulsar’s mode changes are caused by the ejection of clumps of matter from the system. These clumps, which they call “cosmic cannonballs”, are formed when the gas from the companion star accumulates around the pulsar and becomes unstable. The pulsar then flings these clumps away at speeds of up to 10% of the speed of light, creating flashes of light that are detected by the telescopes.
The cosmic cannonballs are launched every few minutes and have masses ranging from 10^15 to 10^17 grams, equivalent to small asteroids or large mountains. They carry away energy and angular momentum from the system, affecting the evolution of the binary. The researchers estimate that the pulsar will consume its companion in about 100 million years.
The pulsar J1023 is one of the few known examples of transitional millisecond pulsars, which are thought to be neutron stars that are spun up by accreting matter from their companions and become faster and brighter over time. By observing these systems, astronomers can learn more about how neutron stars evolve and interact with their environments.
The researchers also compared J1023 with another transitional millisecond pulsar, PSR J1227-4853, which was discovered by Baglio and her colleagues in 20152. They found that both systems show similar mode changes and cosmic cannonball ejections, suggesting that this phenomenon is common among these types of pulsars.
The researchers plan to continue monitoring J1023 and other transitional millisecond pulsars with different telescopes and wavelengths, to better understand their properties and dynamics. They also hope to find more examples of these systems in the future, using new facilities such as the Square Kilometre Array (SKA), a radio telescope project that will be built in Australia and South Africa.