COVENTRY, United Kingdom — Scientists have made an extraordinary discovery that enhances our understanding of how stars evolve. They found a rare type of white dwarf pulsar, a small and dense star formed when a low-mass star burns all of its fuel and sheds its outer layers.
White dwarfs provide valuable insights into the process of star formation and evolution, often being referred to as “stellar fossils.” White dwarf pulsars are unique as they consist of a rapidly spinning white dwarf star and a neighboring red dwarf star. The white dwarf emits powerful beams of electrical particles and radiation that cause the entire system to periodically brighten and fade. The cause of these strong magnetic fields remains unclear.
One theory explaining the magnetic fields is the “dynamo model,” which suggests that white dwarfs possess electrical generators in their cores, similar to Earth but much more powerful. To test this theory, scientists needed to search for other white dwarf pulsars to confirm their predictions.
In an astronomical breakthrough, scientists described the discovery of a second known white dwarf pulsar named J1912-4410. This star system, located 773 light years away from Earth, spins 300 times faster than our planet. While its size resembles that of Earth, it’s at least as massive as the Sun. A teaspoon of white dwarf material would weigh around 15 tons. The cool temperature of J1912-4410 indicates its advanced age.
“The origin of magnetic fields is a big open question in many fields of astronomy, and this is particularly true for white dwarf stars,” says University of Warwick researcher Dr. Ingrid Pelisoli in a media release. “The magnetic fields in white dwarfs can be more than a million times stronger than the magnetic field of the Sun, and the dynamo model helps to explain why. The discovery of J1912−4410 provided a critical step forward in this field.”
To find candidates for the study, researchers used data from various surveys, focusing on systems with similar characteristics to the previously discovered AR Scorpii (AR Sco). After observing several candidates, they found one that exhibited similar light variations to AR Sco. Further observations confirmed that this system emitted radio and X-ray signals in our direction every five minutes, indicating the presence of a white dwarf pulsar.
The discovery of J1912-4410 confirms the predictions made by the dynamo model, including the cool temperature of the white dwarf, its fast spinning, and the gravitational effect it has on its companion star. This research demonstrates the progress of science and how predictions can be tested to advance our understanding.
Dr. Pelisoli is among the researchers supported by a generous philanthropic donation to the University of Warwick, allowing them to explore the vast frontiers of astronomy and astrophysics. Another complementary study led by Axel Schwope from the Leibniz Institute for Astrophysics Potsdam confirmed the unusual nature of the new object and solidified white dwarf pulsars as a new class of stars.
The study is published in the journal Nature Astronomy.
StudyFinds’ Matt Higgins contributed to this report.